Magnetic cores and coil components

Abstract

To provide a magnetic core and a coil component which are excellent in magnetic permeability, core loss and DC superposition characteristics and voltage resistance.SOLUTION: A magnetic core has a metal magnetic powder-containing resin containing metal magnetic powder. The metal magnetic powder-containing resin has metal magnetic powder. The metal magnetic power has large-diameter powder, middle-diameter powder, and small-diameter powder. The large-diameter powder has a particle diameter of 10 μm or more and 60 μm or less. The middle-diameter powder has a particle diameter of 2.0 μm or more and less than 10 μm. The small-diameter powder has a particle diameter of 0.1 μm or more and less than 2.0 μm. The large-diameter powder contains nanocrystals. An existence ratio of the large-diameter powder to the metal magnetic powder is 39% or more and 91% or less in terms of an area ratio in a cut surface of the magnetic core.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a magnetic core and a coil component. [Background technology]

[0002] In the field of electronic devices, surface-mounted coil components are increasingly being used as inductors for power supplies. One specific structure of surface-mounted coil components is a planar coil structure that applies printed circuit board technology.

[0003] Patent Document 1 proposes a coil component having a magnetic core made of two or more types of magnetic metal powders with different particle sizes, and shows that using two or more types of magnetic metal powders with different particle sizes improves magnetic permeability and reduces core loss. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-103287 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, there has been a demand for magnetic cores with even better characteristics. The present invention has been made in view of this situation, and its object is to provide a magnetic core and a coil component that are excellent in magnetic permeability, core loss, DC bias characteristics, and voltage resistance. [Means for solving the problem]

[0006] In order to achieve the above object, the magnetic core according to the present invention comprises: A magnetic core having a metal magnetic powder-containing resin containing metal magnetic powder, The metal magnetic powder-containing resin contains metal magnetic powder, The metal magnetic powder includes large-diameter powder, medium-diameter powder, and small-diameter powder, The large-diameter powder has a particle diameter of 10 μm or more and 60 μm or less, The medium-sized powder has a particle diameter of 2.0 μm or more and less than 10 μm, The small-diameter powder has a particle diameter of 0.1 μm or more and less than 2.0 μm, the large-diameter powder comprises nanocrystals; The ratio of the large-diameter powder to the metal magnetic powder is 39% or more and 91% or less in terms of area ratio on the cut surface of the magnetic core.

[0007] The magnetic core according to the present invention has the above-described configuration, and is therefore excellent in magnetic permeability, core loss, DC bias characteristics, and voltage resistance.

[0008] The medium-sized powder may include nanocrystals.

[0009] The small diameter powder may include permalloy.

[0010] The nanocrystals may be Fe-based nanocrystals.

[0011] The Fe-based nanocrystals may comprise Fe and M; M may be at least one selected from Nb, Hf, Zr, Ta, Mo, W and V.

[0012] The metal magnetic powder may be coated with an insulating material.

[0013] A coil component according to the present invention includes the above-described magnetic core and a coil. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a perspective view of a coil component according to an embodiment of the present invention. [Figure 2] FIG. 2 is an exploded perspective view of the coil component shown in FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III shown in FIG. [Figure 4A] FIG. 4A is a cross-sectional view taken along line IV-IV shown in FIG. [Figure 4B] FIG. 4B is an enlarged cross-sectional view of a main portion near the terminal electrode in FIG. 4A. [Figure 5] FIG. 5 is a schematic diagram of insulating coated metal magnetic powder. [Figure 6] Figure 6 is an SEM image of the cross section of the magnetic core of sample No. 10. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, the present invention will be described based on the embodiments shown in the drawings.

[0016] One embodiment of the coil component according to the present invention is a coil component 2 shown in Figures 1 to 4. As shown in Figure 1, the coil component 2 has a rectangular, flat magnetic core 10 and a pair of terminal electrodes 4, 4 attached to both ends of the magnetic core 10 in the X-axis direction. The terminal electrodes 4, 4 cover the end face of the magnetic core 10 in the X-axis direction and also partially cover the upper surface 10a and lower surface 10b of the magnetic core 10 in the Z-axis direction near the end face of the X-axis direction. Furthermore, the terminal electrodes 4, 4 also partially cover a pair of side surfaces of the magnetic core 10 in the Y-axis direction.

[0017] As shown in FIG. 2, the magnetic core 10 is made up of an upper core 15 and a lower core 16, and has an insulating substrate 11 in the center in the Z-axis direction.

[0018] The insulating substrate 11 is preferably made of a general printed circuit board material in which glass cloth is impregnated with epoxy resin, but there is no particular limitation.

[0019] In the present embodiment, the resin substrate 11 has a rectangular shape, but may have other shapes. There are no particular limitations on the method for forming the resin substrate 11, and it may be formed by, for example, injection molding, a doctor blade method, screen printing, or the like.

[0020] An internal electrode pattern consisting of a circular spiral internal conductor passage 12 is formed on the upper surface (one of the main surfaces) in the Z-axis direction of the insulating substrate 11. The internal conductor passage 12 will eventually become a coil. There are no particular restrictions on the material of the internal conductor passage 12.

[0021] A connection end 12a is formed at the inner peripheral end of the spiral-shaped internal conductor passage 12. A lead contact 12b is formed at the outer peripheral end of the spiral-shaped internal conductor passage 12 so as to be exposed along one end of the magnetic core 10 in the X-axis direction.

[0022] An internal electrode pattern consisting of spiral internal conductor passages 13 is formed on the lower surface (the other main surface) in the Z-axis direction of the insulating substrate 11. The internal conductor passages 13 will eventually become coils. There are no particular restrictions on the material of the internal conductor passages 13.

[0023] A connection end 13a is formed at the inner peripheral end of the spiral-shaped internal conductor passage 13. Furthermore, a lead contact 13b is formed at the outer peripheral end of the spiral-shaped internal conductor passage 13 so as to be exposed along one end of the magnetic core 10 in the X-axis direction.

[0024] 3, connection end 12a and connection end 13a are formed on opposite sides of insulating substrate 11 in the Z-axis direction, and are formed at the same position in the X-axis and Y-axis directions. They are electrically connected via through-hole electrodes 18 embedded in through-holes 11i formed in insulating substrate 11. In other words, spiral-shaped internal conductor path 12 and similarly spiral-shaped internal conductor path 13 are electrically connected in series via through-hole electrodes 18.

[0025] When viewed from the top surface 11a of the insulating substrate 11, the spiral-shaped internal conductor passage 12 forms a counterclockwise spiral from the lead contact 12b at the outer circumferential end to the connection end 12a at the inner circumferential end.

[0026] In contrast, the spiral-shaped internal conductor passage 13 viewed from the top surface 11a side of the insulating substrate 11 forms a counterclockwise spiral from the connecting end 13a, which is the inner peripheral end, to the lead contact 13b, which is the outer peripheral end.

[0027] This allows the directions of magnetic fluxes generated by current flowing through the spiral internal conductor paths 12 and 13 to coincide, and the magnetic fluxes generated in the spiral internal conductor paths 12 and 13 to overlap and reinforce each other, thereby achieving a large inductance.

[0028] Upper core 15 has a cylindrical center leg 15a that protrudes downward in the Z-axis direction at the center of the rectangular plate-shaped core body, and plate-shaped side legs 15b that protrude downward in the X-axis direction at both ends of the rectangular plate-shaped core body in the Y-axis direction.

[0029] The lower core 16 has a rectangular flat plate shape similar to the core body of the upper core 15, and the middle leg portion 15a and the side leg portion 15b of the upper core 15 are connected to the center and the end portion in the Y-axis direction of the lower core 16, respectively, to form an integrated structure.

[0030] 2, magnetic core 10 is depicted as being separated into upper core 15 and lower core 16, but these may be integrally formed using a resin containing magnetic metal powder. Also, center leg 15a and / or side leg 15b formed on upper core 15 may be formed on lower core 16. In either case, magnetic core 10 forms a completely closed magnetic circuit, and no gaps exist within the closed magnetic circuit.

[0031] As shown in Figure 2, a protective insulating layer 14 is interposed between the upper core 15 and the internal conductor passage 12, providing insulation between them. A rectangular sheet-like protective insulating layer 14 is also interposed between the lower core 16 and the internal conductor passage 13, providing insulation between them. A circular through-hole 14a is formed in the center of the protective insulating layer 14. A circular through-hole 11h is also formed in the center of the insulating substrate 11. Through these through-holes 14a and 11h, the middle leg 15a of the upper core 15 extends toward the lower core 16 and is connected to the center of the lower core 16.

[0032] 4A and 4B, in this embodiment, the terminal electrode 4 has an inner layer 4a that contacts the end face in the X-axis direction of the magnetic core 10, and an outer layer 4b that is formed on the surface of the inner layer 4a. The inner layer 4a also covers parts of the upper surface 10a and the lower surface 10b of the magnetic core 10 near the end face in the X-axis direction of the magnetic core 10, and the outer surface of the inner layer 4a is covered by the outer layer 4b.

[0033] In this embodiment, the magnetic core 10 is made of a resin containing magnetic metal powder. The resin containing magnetic metal powder is a magnetic material in which magnetic metal powder is mixed into resin.

[0034] In this embodiment, when the magnetic core 10 is cut at an arbitrary cross section and the cut surface is observed, three sizes of metal magnetic powder are observed: large-diameter powder, medium-diameter powder, and small-diameter powder. In other words, the metal magnetic powder has large-diameter powder, medium-diameter powder, and small-diameter powder. Specifically, when the cut surface of the magnetic core 10 is observed using an SEM, it appears as shown in FIG. 6. Note that FIG. 6 shows Sample No. 10, an example of an embodiment described later.

[0035] The large particle diameter is 10 μm or more and 60 μm or less in particle diameter (equivalent circle diameter), the medium particle diameter is 2.0 μm or more and less than 10 μm, and the small particle diameter is 0.1 μm or more and less than 2.0 μm.

[0036] The large-diameter powder contains nanocrystals. Here, nanocrystals refer to crystals with a grain size on the nano-order, that is, crystals of 1 nm or more and 100 nm or less. While it is not necessary for all of the large-diameter powder to contain nanocrystals, it is preferable that 30% or more of the large-diameter powder contains nanocrystals on a number basis.

[0037] Furthermore, the medium-sized powder may contain nanocrystals, and 30% or more of the medium-sized powder may contain nanocrystals on a number basis. When the medium-sized powder contains nanocrystals, the magnetic permeability is further improved.

[0038] In powders containing nanocrystals, it is common for a single grain of powder to contain many nanocrystals, meaning that the particle size of the powder is different from the crystal grain size.

[0039] In this embodiment, the large-diameter powder contains nanocrystals, which improves the magnetic permeability of the magnetic core and reduces core loss. In addition, the DC bias characteristics and withstand voltage are favorably maintained without significant degradation.

[0040] The nanocrystals will be described in more detail below, along with the compositions of the large and medium diameter powders.

[0041] The nanocrystals of this embodiment are preferably Fe-based nanocrystals, which are crystals with nano-order particle sizes and Fe crystal structures of bcc (body-centered cubic lattice structure).

[0042] In this embodiment, the Fe-based nanocrystals preferably have an average particle size of 5 to 30 nm. A soft magnetic alloy in which such Fe-based nanocrystals are precipitated tends to have a high saturation magnetic flux density and a low coercive force.

[0043] The composition of the Fe-based nanocrystals in this embodiment is arbitrary. For example, they may contain M in addition to Fe. M is one or more elements selected from Nb, Hf, Zr, Ta, Mo, W, and V.

[0044] The composition of the metal magnetic powder containing Fe-based nanocrystals is arbitrary. For example, Composition formula (Fe (1-( α + β )) X1αX2β) (1-(a+b+c+d+e+g+f)) M a B b P c Si d C e S f Ti g A soft magnetic alloy consisting essentially of X1 is at least one selected from the group consisting of Co and Ni; X2 is one or more selected from the group consisting of Al, Mn, Ag, Zn, Sn, As, Sb, Cu, Cr, Bi, N, O and rare earth elements; M is one or more selected from the group consisting of Nb, Hf, Zr, Ta, Mo, W and V; 0.020≦a≦0.14 0.020 <b≦0.20 0≦c≦0.15 0≦d≦0.14 0≦e≦0.030 0≦f≦0.010 0≦g≦0.0010 α≧0 β≧0 0≦α+β≦0.50 may be.

[0045] Each component of the metal magnetic powder containing Fe-based nanocrystals will be described in detail below.

[0046] M is one or more elements selected from the group consisting of Nb, Hf, Zr, Ta, Mo, W and V.

[0047] The M content (a) satisfies 0.020≦a≦0.14. If a is small, crystals with a particle size larger than nanocrystals are likely to be produced during the production of the metal magnetic powder. This tends to result in a lower resistivity, a higher coercive force, and a lower magnetic permeability of the metal magnetic powder. If a is large, the saturation magnetic flux density of the metal magnetic powder tends to decrease.

[0048] The content (b) of B satisfies 0.020 < b ≤ 0.20. When b is small, crystals with a particle size larger than that of nanocrystals are likely to occur during the production of the metallic magnetic powder. Then, the specific resistance of the metallic magnetic powder tends to be low, the coercive force tends to be high, and the magnetic permeability tends to be low. When b is large, the saturation magnetic flux density of the metallic magnetic powder tends to decrease.

[0049] The content (c) of P satisfies 0 ≤ c ≤ 0.15. That is, P may not be contained. When c is large, the saturation magnetic flux density of the metallic magnetic powder tends to decrease.

[0050] The content (d) of Si satisfies 0 ≤ d ≤ 0.14. That is, Si may not be contained. When d is large, the coercive force of the metallic magnetic powder tends to increase.

[0051] The content (e) of C satisfies 0 ≤ e ≤ 0.030. That is, C may not be contained. When e is large, the specific resistance of the metallic magnetic powder decreases, and the coercive force tends to increase.

[0052] The content (f) of S satisfies 0 ≤ f ≤ 0.010. That is, S may not be contained. When f is large, the coercive force tends to increase.

[0053] The content (g) of Ti satisfies 0 ≤ f ≤ 0.0010. That is, Ti may not be contained. When g is large, the coercive force tends to increase.

[0054] The content (1-(a + b + c + d + e + f + g)) of Fe preferably satisfies 0.73 ≤ (1-(a + b + c + d + e + f + g)) ≤ 0.95. By setting (1-(a + b + c + d + e + f + g)) within the above range, Fe-based nanocrystals are likely to be obtained.

[0055] Also, a part of Fe may be replaced with X1 and / or X2.

[0056] X1 is one or more selected from the group consisting of Co and Ni. Regarding the content of X1, α may be 0. That is, X1 may not be contained. Furthermore, the number of atoms of X1 is preferably 40 at% or less, where the number of atoms in the entire composition is 100 at%. That is, it is preferable to satisfy 0≦α{1−(a+b+c+d+e+f+g)}≦0.40.

[0057] X2 is one or more elements selected from the group consisting of Al, Mn, Ag, Zn, Sn, As, Sb, Cu, Cr, Bi, N, O, and rare earth elements. Regarding the content of X2, β may be 0. That is, X2 may not be contained. Furthermore, the number of X2 atoms is preferably 3.0 at% or less, where the number of atoms in the entire composition is 100 at%. That is, it is preferable to satisfy the relationship 0≦β{1−(a+b+c+d+e+f+g)}≦0.030.

[0058] The range of substitution amount of X1 and / or X2 for Fe may be half or less of Fe on an atomic number basis. In other words, 0≦α+β≦0.50 may be satisfied. If α+β>0.50, it becomes difficult to obtain Fe-based nanocrystals.

[0059] Elements other than those mentioned above may be contained within a range that does not significantly affect the properties, for example, 0.1% by weight or less relative to 100% by weight of the metal magnetic powder.

[0060] In this embodiment, in any cross section of the magnetic core 10, the abundance ratio of the large diameter powder to the metal magnetic powder is 39% or more and 91% or less in area ratio.

[0061] By making the area ratio of the large-diameter powder 39% or more, the magnetic permeability of the magnetic core is improved and core loss is reduced. In addition, the DC bias characteristics and withstand voltage are maintained favorably without any significant degradation.

[0062] Furthermore, by setting the area ratio of the large-diameter powder to 91% or less, the magnetic permeability of the magnetic core is improved. Furthermore, the DC bias characteristics and withstand voltage are maintained favorably without a significant decrease. Furthermore, the core loss is maintained favorably without a significant increase.

[0063] The ratio of the large-diameter powder to the metal magnetic powder is preferably 59% or more and 86% or less in area ratio, and more preferably 74% or more and 86% or less. In particular, when the ratio of the large-diameter powder is 74% or more and 86% or less, the core loss becomes even smaller when the medium-diameter powder contains nanocrystals.

[0064] In this embodiment, in any cross section of the magnetic core 10, the ratio of the medium-sized powder to the small-sized powder is preferably 0.73 to 5.7 in area ratio, and more preferably 0.73 to 2.3. The smaller the ratio of the medium-sized powder to the small-sized powder, the better the magnetic permeability of the magnetic core. On the other hand, the greater the ratio of the medium-sized powder to the small-sized powder, the better the DC bias characteristics.

[0065] In this embodiment, the small-diameter powder preferably contains permalloy, and 30% or more of the small-diameter powder may contain permalloy by number. When the small-diameter powder contains permalloy, the magnetic permeability is further improved.

[0066] All of the metal magnetic powder may contain nanocrystals, but if all of the metal magnetic powder contains nanocrystals, the content of metal magnetic powder in the magnetic core 10 is likely to decrease, and magnetic permeability is likely to decrease. Nanocrystals are also expensive. Therefore, it is preferable to simultaneously contain metal magnetic powder containing nanocrystals and metal magnetic powder not containing nanocrystals. Specifically, the proportion of metal magnetic powder containing nanocrystals is preferably 40 wt% to 90 wt% by weight.

[0067] The permalloy in this embodiment refers to a Ni-Fe alloy containing 28% or more by weight of Ni, with the remainder being Fe and other elements. There are no particular restrictions on the content of the other elements, but the content is 8% by weight or less when the Ni-Fe alloy is taken as 100% by weight.

[0068] The Ni content in the permalloy is preferably 40 to 85% by weight, and particularly preferably 75 to 82% by weight. By keeping the Ni content within the above range, the initial permeability is improved and the core loss is reduced.

[0069] Furthermore, the metal magnetic powder according to this embodiment is preferably insulated coated as shown in FIG. 5. It is even more preferable that the large-diameter powder, medium-diameter powder, and small-diameter powder are all insulated coated. Insulating the metal magnetic powder particularly improves the withstand voltage. Note that "insulating coated" refers to the case where 50% or more of the powder is insulated coated.

[0070] There are no particular restrictions on the material of the insulating coating 22, and any insulating coating commonly used in this technical field can be used. A coating containing glass made of SiO2 or a phosphate chemical conversion coating containing phosphate is preferred. For metal magnetic powder containing permalloy, it is particularly preferred to use a coating containing glass made of SiO2. Furthermore, any insulating coating method can be used, and any method commonly used in this technical field can be used.

[0071] There is no particular limitation on the thickness of the insulating coating 22. The average thickness of the insulating coating 22 of the metal magnetic powder is preferably 5 to 45 nm, and particularly preferably 10 to 35 nm.

[0072] The particle size of the insulating coated metal magnetic powder is the length d1 in Figure 5. The length d2 in Figure 5, i.e., the maximum thickness of the insulating coating on the metal magnetic powder, is the thickness of the insulating coating on the metal magnetic powder. The insulating coating does not necessarily have to cover the entire surface of the metal magnetic powder. Metal magnetic powder with 50% or more of its surface covered with the insulating coating is considered to be insulating coated metal magnetic powder.

[0073] When the metal magnetic powder in this embodiment has the above-described configuration, it is possible to obtain a magnetic core 10 that is excellent in all of initial permeability, core loss, DC bias characteristics, and withstand voltage.

[0074] The content of the metal magnetic powder in the resin containing the metal magnetic powder is preferably 90 to 99% by weight, and more preferably 95 to 99% by weight. If the amount of metal magnetic powder relative to the resin is reduced, the saturation magnetic flux density and magnetic permeability will decrease, and conversely, if the amount of metal magnetic powder is increased, the saturation magnetic flux density and magnetic permeability will increase. Therefore, the saturation magnetic flux density and magnetic permeability can be adjusted by the amount of metal magnetic powder.

[0075] The resin contained in the metal magnetic powder-containing resin functions as an insulating binder. It is preferable to use a liquid epoxy resin or a powder epoxy resin as the resin material. The resin content is preferably 1 to 10% by weight, and more preferably 1 to 5% by weight. When mixing the metal magnetic powder and the resin, it is preferable to use a resin solution to obtain a metal magnetic powder-containing resin solution. There are no particular limitations on the solvent for the resin solution.

[0076] A method for manufacturing the coil component 2 will be described below.

[0077] First, the spiral internal conductor paths 12, 13 are formed by plating on the insulating substrate 11. There are no particular limitations on the plating conditions, and they may be formed by a method other than plating.

[0078] Next, protective insulating layers 14 are formed on both sides of the insulating substrate 11 on which the internal conductor paths 12 and 13 have been formed. There are no particular limitations on the method for forming the protective insulating layer 14. For example, the protective insulating layer 14 can be formed by immersing the insulating substrate 11 in a resin solution diluted with a high-boiling point solvent and drying it.

[0079] Next, magnetic core 10 is formed by combining upper core 15 and lower core 16 as shown in Fig. 2. To do this, the above-mentioned resin solution containing metal magnetic powder is applied to the surface of insulating substrate 11 on which protective insulating layer 14 is formed. There are no particular limitations on the application method, but application by printing is common.

[0080] The metal magnetic powder in this embodiment is produced by mixing multiple metal magnetic powders with different particle size distributions, etc. Here, by controlling the particle size distribution and mixing ratio of the multiple metal magnetic powders, it is possible to control the cross-sectional area ratio of the large-diameter powder, medium-diameter powder, and small-diameter powder in the final magnetic core 10 obtained.

[0081] Here is an example of a method for relatively easily controlling the cross-sectional area ratios of large-diameter powder, medium-diameter powder, and small-diameter powder in magnetic core 10. In this method, metal magnetic powders that will primarily become large-diameter powder, metal magnetic powders that will primarily become medium-diameter powder, and metal magnetic powders that will primarily become small-diameter powder are separately prepared in the final magnetic core 10. In this case, the D50 of the metal magnetic powder that will primarily become large-diameter powder is set to 15 to 40 μm, the D50 of the metal magnetic powder that will primarily become medium-diameter powder is set to 3.0 to 8.0 μm, and the D50 of the metal magnetic powder that will primarily become small-diameter powder is set to 0.5 to 1.5 μm, thereby sufficiently reducing the variation in particle size of each metal magnetic powder.

[0082] The large-diameter, medium-diameter, and small-diameter powders are preferably spherical. In this embodiment, "spherical" specifically refers to a sphericity of 0.9 or more. The sphericity can be measured using an image particle size distribution analyzer.

[0083] Next, a method for producing a metal magnetic powder containing nanocrystals (particularly Fe-based nanocrystals) will be described. Any method can be used to produce a metal magnetic powder containing nanocrystals (particularly Fe-based nanocrystals), but from the perspective of making it easier to form the metal magnetic powder containing nanocrystals (particularly Fe-based nanocrystals) into a spherical shape, gas atomization is preferred.

[0084] In the gas atomization method, first, pure metals of each metal element contained in the final metal magnetic powder are prepared and weighed so as to have the same composition as the final metal magnetic powder. Then, the pure metals of each metal element are melted and mixed to prepare a master alloy. There are no particular limitations on the method for melting the pure metal, but one method is to melt the metal by high-frequency heating after evacuating the chamber. The master alloy and the final soft magnetic alloy usually have the same composition. Next, the prepared master alloy is heated and melted to obtain molten metal (molten metal). There are no particular limitations on the temperature of the molten metal, but it can be, for example, 1200 to 1500°C.

[0085] The molten alloy is then sprayed into the chamber to produce metal magnetic powder. The particle size distribution of the metal magnetic powder can be controlled by methods commonly used in gas atomization. At this time, it is preferable to set the gas spray temperature to 50 to 200°C and the vapor pressure in the chamber to 4 hPa or less. This is because the heat treatment described below makes it easier to obtain metal magnetic powder containing Fe-based nanocrystals. At this point, the metal magnetic powder may consist of only amorphous material, or it may have a nanoheterostructure. In this embodiment, a nanoheterostructure refers to a structure in which nanocrystals with a particle size of 30 nm or less exist in an amorphous material.

[0086] Next, it is preferable to heat-treat the produced metal magnetic powder. Heat treatment is always required when the metal magnetic powder is composed only of amorphous material, but heat treatment is not necessarily required when the metal magnetic powder has a nanoheterostructure, because the metal magnetic powder already contains nanocrystals.

[0087] For example, heat treatment at 400-600°C for 0.5-10 minutes can prevent the individual metal magnetic powder particles from sintering and coarsening while promoting element diffusion, allowing the particles to reach a thermodynamic equilibrium state in a short time and eliminating strain and stress. As a result, it becomes easier to obtain metal magnetic powder containing Fe-based nanocrystals. Note that the metal magnetic powder containing Fe-based nanocrystals after heat treatment may or may not contain amorphous material.

[0088] There are no particular limitations on the method for calculating the average particle size of the Fe-based nanocrystals contained in the metal magnetic powder obtained by heat treatment. For example, it can be calculated by observation using a transmission electron microscope. There are also no particular limitations on the method for confirming that the crystal structure is a bcc (body-centered cubic lattice structure). For example, it can be confirmed using X-ray diffraction measurement.

[0089] Next, the solvent in the resin solution containing the magnetic metal powder that has been applied by printing is volatilized to form the magnetic core 10.

[0090] Furthermore, the density of the magnetic core 10 is increased. There are no particular limitations on the method for increasing the density of the magnetic core 10, but one example is a method using a press treatment.

[0091] The upper surface 11a and the lower surface 11b of the magnetic core 10 are then ground to a predetermined thickness. The resin is then cross-linked by thermal curing. The grinding method is not particularly limited, but examples include a method using a fixed grindstone. The temperature and time for thermal curing are also not particularly limited, and can be appropriately controlled depending on the type of resin, etc.

[0092] Thereafter, the insulating substrate 11 on which the magnetic cores 10 are formed is cut into individual pieces. There is no particular limitation on the cutting method, but dicing may be used, for example.

[0093] By the above method, the magnetic core 10 before the terminal electrodes 4 are formed as shown in Fig. 1 is obtained. Before cutting, the magnetic core 10 is integrally connected in the X-axis direction and the Y-axis direction.

[0094] After cutting, etching is performed on the individual magnetic cores 10. The conditions for the etching are not particularly limited.

[0095] Next, an electrode material for forming the inner layer 4a is prepared. Any type of electrode material can be used. For example, a conductive powder-containing resin can be used, which is a thermosetting resin such as an epoxy resin similar to the epoxy resin used in the metal magnetic powder-containing resin described above, containing a conductive powder such as Ag powder. When using a conductive powder-containing resin as the electrode material, the electrode material is applied to both ends of the etched magnetic core 10 in the X-axis direction, and the thermosetting resin is cured by heating to form the inner layer 4a.

[0096] Next, terminal plating is applied to the product on which the inner layer 4a has been formed by barrel plating to form the outer layer 4b. The outer layer 4b may have a multi-layer structure of two or more layers. There are no particular restrictions on the method or material for forming the outer layer 4b, but it can be formed, for example, by applying Ni plating to the inner layer 4a and then applying Sn plating to the Ni plating. The coil component 2 can be manufactured by the above method.

[0097] In this embodiment, the magnetic core 10 is made of resin containing metal magnetic powder, and the resin exists between the metal magnetic powder particles, creating a minute gap that increases the saturation magnetic flux density. This prevents magnetic saturation without forming an air gap between the upper core 15 and the lower core 16. Therefore, there is no need to machine the magnetic core with high precision to form the gap.

[0098] Furthermore, in the coil component 2 according to this embodiment, forming the coil as an assembly on the substrate surface allows for extremely high coil positioning accuracy, making it possible to reduce the size and thickness. Furthermore, in this embodiment, a metallic magnetic material is used for the magnetic body, which has better DC bias characteristics than ferrite, so the formation of a magnetic gap can be omitted.

[0099] The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention. For example, even if the coil components have forms other than those shown in Figures 1 to 4, all coil components having a coil covered with the resin containing metal magnetic powder described above are coil components of the present invention. [Example]

[0100] The present invention will be described below based on examples.

[0101] A toroidal core was fabricated to evaluate the properties of the resin containing magnetic metal powder in the coil component according to the present invention. The fabrication method of the toroidal core will be described below.

[0102] First, large diameter powder 1, medium diameter powder 1, and small diameter powder 1 to be contained in the metal magnetic powder were prepared in order to produce the metal magnetic powder contained in the toroidal core.

[0103] First, nanocrystalline alloy powders 1 to 3 with the compositions (atomic ratios) shown in Table 1 were prepared as large-diameter powder 1 and medium-diameter powder 1. Note that the compositions in Table 1 have been rounded to one decimal place, so the total may not add up to 100.0%.

[0104] [Table 1]

[0105] A method for producing the nanocrystalline alloy powder used for the large-diameter powder 1 and the medium-diameter powder 1 will be described.

[0106] First, raw material metals were weighed so as to have the alloy composition shown in Table 1, and melted by high-frequency heating to prepare master alloys.

[0107] The prepared master alloy was then heated and melted to form a molten metal at 1250°C. The metal was then sprayed by gas atomization to produce powder. The gas spray temperature was 150°C, and the vapor pressure in the chamber was 3.8 hPa. Vapor pressure adjustment was performed using Ar gas with a dew point adjustment. The particle size distribution was controlled to achieve the D50 shown in Tables 2 to 5.

[0108] Each powder was then heat treated at 500°C for 5 minutes to produce nanocrystalline alloy powder.

[0109] When amorphous powder was used as the large-diameter powder 1, Fe-based amorphous powder (manufactured by Epson Atmix Corporation) with a D50 of 24 μm was prepared. When amorphous powder was used as the medium-diameter powder, Fe-based amorphous powder (manufactured by Epson Atmix Corporation) with a D50 of 3.0 μm was prepared. In Tables 2 to 9 shown below, the Fe-based amorphous powder with a D50 of 24 μm is referred to as amorphous powder 1, and the Fe-based amorphous powder with a D50 of 3.0 μm is referred to as amorphous powder 2. It is listed as powder 2.

[0110] As the small diameter powder 1, pure iron powder and permalloy powder (Ni content: 78.5 wt%) were prepared.

[0111] Next, the large diameter powder 1, the medium diameter powder 1 and the small diameter powder 1 (excluding the pure iron powder) were coated.

[0112] The coating on the large-diameter powder 1 and the medium-diameter powder 1 was carried out by forming a phosphate conversion coating containing phosphate (hereinafter, sometimes simply referred to as a phosphate conversion coating). The phosphate conversion coating was formed by spraying a solution containing phosphate onto the large-diameter powder 1 and the medium-diameter powder 1. The average thickness of the phosphate conversion coating was set to 30 nm.

[0113] The coating for the small-diameter powder 1 (excluding pure iron powder) was performed by forming an insulating film (hereinafter sometimes simply referred to as a glass coat) made of glass containing SiO2. The glass coat was formed by spraying a solution containing SiO2 onto the metal magnetic powder. The average thickness of the glass coat was set to 30 nm.

[0114] Then, large diameter powder 1, medium diameter powder 1 and small diameter powder 1 were mixed so that the compounding ratios by weight of Tables 2 to 5 were obtained, thereby producing a metal magnetic powder.

[0115] [Table 2]

[0116] [Table 3]

[0117] [Table 4]

[0118] [Table 5]

[0119] The metal magnetic powder was then mixed with an epoxy resin to prepare a resin containing the metal magnetic powder. The weight ratio of the metal magnetic powder with the insulating coating formed in the resin containing the metal magnetic powder was 97.5% by weight. The epoxy resin used was a phenol novolac epoxy resin.

[0120] The obtained resin containing the metal magnetic powder was then filled into a mold of a predetermined toroidal shape and heated at 100°C for 5 hours to volatilize the solvent. 2After pressing at a pressure of 1000 kJ / cm, it was ground with a fixed grinding wheel to a uniform thickness of 0.7 mm. It was then heat-cured at 170°C for 90 minutes to crosslink the epoxy resin and obtain a toroidal core (outer diameter 15 mm, inner diameter 9 mm, thickness 0.7 mm).

[0121] The obtained resin containing metal magnetic powder was then filled into a mold of a predetermined rectangular parallelepiped shape. A rectangular parallelepiped magnetic material (4 mm x 4 mm x 1 mm) was obtained in the same manner as for the toroidal core. Furthermore, terminal electrodes with a width of 1.3 mm were provided on both ends of one of the 4 mm x 4 mm faces of the rectangular parallelepiped magnetic material. The distance between the terminal electrodes was 1.4 mm.

[0122] Next, the proportions of the large diameter powder 2, the medium diameter powder 2 and the small diameter powder 2 in the obtained toroidal core were measured.

[0123] The obtained toroidal core was cut at an arbitrary cross section, and the cut surface was observed using an SEM at 1000x magnification with an observation area of 0.128mm x 0.96mm. Powders with particle diameters (circle-equivalent diameters) in the cross section of 10µm to 60µm were designated as large-diameter powder 2, powders with particle diameters of 2.0µm to less than 10µm as medium-diameter powder 2, and powders with particle diameters of 0.1µm to less than 2.0µm as small-diameter powder 2. The area ratios (cross-sectional area ratios) of the large-diameter powder 2, medium-diameter powder 2, and small-diameter powder 2 on the cut surface were then confirmed. To calculate the area ratios, five or more different observation areas were set, and the area ratios of each powder in each observation area were calculated and averaged. The results are shown in Tables 6 to 9.

[0124] Furthermore, for all samples listed in Tables 6 to 9, it was confirmed using SEM / EDS that at least 30% or more of the large diameter powder 2 on a number basis was derived from the large diameter powder 1. It was also confirmed that at least 30% or more of the medium diameter powder 2 was derived from the medium diameter powder 1, and at least 30% or more of the small diameter powder 2 was derived from the small diameter powder 1.

[0125] A coil was wound around the toroidal core, and various properties (initial permeability μi, core loss Pcv) were evaluated. The results are shown in Tables 6 to 9.

[0126] The initial permeability μi was calculated from the inductance (L0) measured by winding a coil with 30 turns and using an LCR meter at a frequency of 1 MHz. In this example, μi of 30 or more was considered good, 35 or more was considered better, 40 or more was considered even better, 45 or more was considered particularly good, and 50 or more was considered best.

[0127] The core loss Pcv was measured by winding a coil with 30 turns on the primary side and 30 turns on the secondary side, using an AC BH analyzer at a magnetic flux density of 10 mT and a frequency of 3 MHz. 3 Below 600kW / m is considered good. 3 It is considered better if it is less than 550kW / m 3 It is considered better if it is less than 500kW / m 3 The following was deemed to be the best case:

[0128] Furthermore, the DC bias characteristics were measured. First, the inductance (L0) was measured when no DC current was applied. Next, the inductance (L1) was measured when a DC current was applied. The magnitude of the DC current when 100×(L0−L1) / L0(%) was 90% was defined as Idc1 (A). In this example, the DC bias characteristics were considered to be good when Idc1 was 3.5 A or more, even better when Idc1 was 4.5 A or more, and best when Idc1 was 5.5 A or more.

[0129] Furthermore, the dielectric breakdown strength was measured by applying a voltage between the terminal electrodes of the rectangular parallelepiped magnetic material and measuring the voltage when a current of 2 mA flowed. In this example, the withstand voltage was determined to be good if it was 200 V or more, even better if it was 700 V or more, even better if it was 750 V or more, even better if it was 800 V or more, and the best if it was 900 V or more.

[0130] [Table 6]

[0131] [Table 7]

[0132] [Table 8]

[0133] [Table 9]

[0134] Samples Nos. 3 to 6 and 6a in Table 6 are examples in which the large-diameter powder 2 is mainly nanocrystalline alloy powder 1, the medium-diameter powder 2 is mainly amorphous powder 2, and the small-diameter powder 2 is mainly pure iron powder, and the blending ratio of each powder was changed.

[0135] Samples Nos. 3 to 6 and 6a, in which the cross-sectional area ratio (L2) of the large diameter powder 2 to the metal magnetic powder was 39% or more and 91% or less, exhibited good initial permeability μi, core loss Pcv, DC bias characteristics and withstand voltage.

[0136] Samples Nos. 8 to 11 in Table 6 are examples in which the large-diameter powder 2 is mainly nanocrystalline alloy powder 1, the medium-diameter powder 2 is mainly amorphous powder 2, and the small-diameter powder 2 is mainly permalloy powder, and the blending ratios of each powder are changed. Samples Nos. 13 to 16 in Table 6 are examples in which the large-diameter powder 2 is mainly nanocrystalline alloy powder 1, the medium-diameter powder 2 is mainly nanocrystalline alloy powder 1, and the small-diameter powder 2 is mainly permalloy powder, and the blending ratios of each powder are changed.

[0137] Samples Nos. 8 to 11 and 13 to 16, in which the cross-sectional area ratio (L2) of the large-diameter powder 2 to the metal magnetic powder was 39% or more and 91% or less, and the small-diameter powder 2 contained permalloy, all had good initial permeability μi, core loss Pcv, DC bias characteristics, and withstand voltage. In particular, the withstand voltage was better than when the small-diameter powder 2 was quasi-iron powder.

[0138] Samples Nos. 18 to 21 in Table 7 are examples in which the large-diameter powder 2 is mainly nanocrystalline alloy powder 2, the medium-diameter powder 2 is mainly amorphous powder 2, and the small-diameter powder 2 is mainly permalloy powder, and the blending ratios of each powder are changed. Samples Nos. 23 to 26 in Table 7 are examples in which the large-diameter powder 2 is mainly nanocrystalline alloy powder 2, the medium-diameter powder 2 is mainly nanocrystalline alloy powder 2, and the small-diameter powder 2 is mainly permalloy powder, and the blending ratios of each powder are changed.

[0139] Samples Nos. 18 to 21 and 23 to 26, in which the cross-sectional area ratio (L2) of the large-diameter powder 2 to the metal magnetic powder was 39% or more and 91% or less, and the small-diameter powder 2 contained permalloy, all had good initial permeability μi, core loss Pcv, DC bias characteristics, and withstand voltage.

[0140] Samples Nos. 48 to 51 in Table 8 are examples in which the large-diameter powder 2 is mainly nanocrystalline alloy powder 3, the medium-diameter powder 2 is mainly amorphous powder 2, and the small-diameter powder 2 is mainly permalloy powder, and the blending ratios of each powder were changed. Samples Nos. 23 to 26 in Table 7 are examples in which the large-diameter powder 2 is mainly nanocrystalline alloy powder 2, the medium-diameter powder 2 is mainly nanocrystalline alloy powder 2, and the small-diameter powder 2 is mainly permalloy powder, and the blending ratios of each powder were changed.

[0141] Samples Nos. 48 to 51, in which the cross-sectional area ratio (L2) of large-diameter powder 2 to metal magnetic powder was 39% or more and 90% or less, and in which small-diameter powder 2 contained permalloy, had good initial permeability μi, core loss Pcv, DC bias characteristics, and withstand voltage.

[0142] Samples Nos. 52 to 55 in Table 8 are examples in which only the blending ratio of medium-diameter powder to small-diameter powder was changed from sample No. 50.

[0143] Even in this case, samples Nos. 52 to 55, in which the cross-sectional area ratio (L2) of large-diameter powder 2 to the metal magnetic powder was 39% or more and 90% or less, and in which small-diameter powder 2 contained permalloy, all exhibited good initial permeability μi, core loss Pcv, DC bias characteristics, and withstand voltage. Furthermore, as the cross-sectional area ratio of medium-diameter powder 2 increased, the DC bias characteristics improved, but the initial permeability μi tended to decrease.

[0144] Table 9 shows the test results for the samples listed in Tables 6 to 8, in which the cross-sectional area ratio of large diameter powder 2 is approximately 80%, and the cross-sectional area ratios of medium diameter powder 2 and small diameter powder 2 are each approximately 10%. It also lists samples Nos. 1, 7, and 12, in which large diameter powder 1 is mainly amorphous powder 1. It was confirmed using STEM that nanocrystals were not observed in large diameter powder 2, particularly for sample No. 12.

[0145] The cross-sectional area ratio (L2) of the large-diameter powder 2 to the metal magnetic powder was 39% or more and 91% or less, and each sample in which the large-diameter powder 2 contained nanocrystals had good initial permeability μi, core loss Pcv, DC bias characteristics, and withstand voltage.

[0146] In contrast, samples Nos. 1, 7, and 12, in which the large-diameter powder 2 did not contain nanocrystals, had significantly increased core loss Pcv.

[0147] Furthermore, when the large-diameter powder 2 is mainly nanocrystalline alloy powder 1 and / or nanocrystalline alloy powder 2, the magnetic permeability μi, core loss Pcv, and DC bias characteristics are particularly good compared to when the large-diameter powder 2 is mainly nanocrystalline alloy powder 3.

[0148] We also compared the results when medium-sized powder 2 was primarily amorphous powder with those when it was primarily nanocrystalline alloy powder. When medium-sized powder 2 was primarily amorphous powder, the DC bias characteristics were better. In contrast, when medium-sized powder 2 was primarily nanocrystalline alloy powder, the magnetic permeability μi and core loss Pcv were better.

[0149] <Experimental Example 2> The magnetic cores shown in Figures 1 to 4A and 4B were fabricated using the resin containing magnetic metal powder used in each of the above examples, and the coil components shown in Figures 1 to 4A and 4B were fabricated. The coil components using the resin containing magnetic metal powder used in each example were coil components with good initial permeability, core loss, and DC bias characteristics. Furthermore, when the small-diameter powder 2 was mainly permalloy powder, the coil components also had good withstand voltage. [Explanation of symbols]

[0150] 2... Coil parts 4…Terminal electrode 4a... Inner layer 4b… Outer layer 10... Magnetic core 11... Insulating substrate 12,13... Internal conductor passage 12a, 13a... Connection end 12b, 13b... Lead contacts 14... Protective insulating layer 15... Upper core 15a…Middle leg 15b... Side leg 16... Lower core 18...Through-hole conductor 20... Insulation coated metal magnetic powder 22... Insulation coating

Claims

1. A magnetic core having a metal magnetic powder-containing resin containing metal magnetic powder, The metal magnetic powder-containing resin contains metal magnetic powder, The metal magnetic powder includes large-diameter powder, medium-diameter powder, and small-diameter powder, The large-diameter powder has a particle diameter of 10 μm or more and 60 μm or less, The medium-sized powder has a particle diameter of 2.0 μm or more and less than 10 μm, The small-diameter powder has a particle diameter of 0.1 μm or more and less than 2.0 μm, the large-diameter powder comprises nanocrystals; the nanocrystals are Fe-based nanocrystals, and the Fe-based nanocrystals include Fe and Nb; The large-diameter powder has an Fe content of 72.9 at% or more and 81.0 at% or less, and an Nb content of 3.1 at% or more and 7.0 at% or less, the abundance ratio of the large-diameter powder to the metal magnetic powder is 39% or more and 91% or less in terms of area ratio on a cut surface of the magnetic core, A magnetic core characterized in that, in any cross section of the magnetic core, the abundance ratio of the medium-diameter powder to the abundance ratio of the small-diameter powder is 0.73 or more and 5.7 or less in area ratio.

2. The magnetic core according to claim 1 , wherein the medium-sized powder contains nanocrystals.

3. 3. The magnetic core according to claim 1, wherein the small-diameter powder contains permalloy.

4. The magnetic core according to any one of claims 1 to 3, wherein the metal magnetic powder is coated with an insulating coating.

5. A coil component comprising the magnetic core according to any one of claims 1 to 4 and a coil.

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