Composite magnetic body and electronic component

Abstract

The present invention provides a composite magnetic body comprising soft magnetic metal particles and non-magnetic ceramic particles having a smaller particle diameter (D50) than the soft magnetic metal particles.

Description

Technical Field

[0001] The present invention relates to a composite magnetic body made of soft magnetic metal particles and an electronic component comprising the composite magnetic body. Background Technology

[0002] Compared to ferrites, metallic magnetic materials have higher saturation magnetic flux density and better DC superposition characteristics. Therefore, in recent years, metallic magnetic materials have been widely used to replace ferrites in electronic components such as inductors, transformers, and choke coils. For example, Patent Document 1 proposes a multilayer inductor using FeCrSi alloy as the magnetic material.

[0003] However, compared with ferrite as an oxide, conventional metallic magnetic materials have poor impedance frequency characteristics and are not suitable for electronic components used in high-frequency applications.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2017-092431 Summary of the Invention

[0007] The problem the invention aims to solve

[0008] The present invention was made in view of the following actual situation, and its purpose is to provide a composite magnetic material with good DC superposition characteristics and good impedance frequency characteristics, and an electronic component using the composite magnetic material.

[0009] Means for solving technical problems

[0010] To achieve the above objectives, the present invention provides a composite magnetic body comprising:

[0011] Soft magnetic metal particles; and

[0012] The non-magnetic ceramic particles have a smaller particle size (D50) than the soft magnetic metal particles.

[0013] The composite magnetic material of the present invention, by having the above-described structure, achieves excellent DC superposition characteristics and improves the frequency characteristics of impedance. Here, "improved frequency characteristics of impedance" refers to the shift of the self-resonant frequency (SRF) of the composite magnetic material to a higher frequency. Furthermore, the self-resonant frequency (SRF) is the frequency at which the impedance reaches its maximum value in the frequency characteristics of impedance.

[0014] Furthermore, soft ferrites such as Mn-Zn ferrites or Ni-Zn ferrites are ceramics, but they are magnetic. Such soft ferrites do not conform to the non-magnetic ceramic particles of the present invention.

[0015] Preferably, the non-magnetic ceramic particles are silicate compounds containing one or more elements selected from copper, zinc, nickel, aluminum, magnesium, and tin.

[0016] Furthermore, it is preferable that the non-magnetic ceramic particles are silicate compounds represented by the general formula α(βZnO·(1-β)CuO)·SiO2.

[0017] In the general formula, α is 1.5 to 2.4, and β is 0.60 to 1.00.

[0018] By using the silicate compound described above as non-magnetic ceramic particles, it is possible to suppress the formation of a reaction phase that hinders the properties of the magnetic material between soft magnetic metal particles and non-magnetic ceramic particles.

[0019] Preferably, the content of the non-magnetic ceramic particles is 0.6 parts by weight or more and 90 parts by weight or less relative to 100 parts by weight of the soft magnetic metal particles. According to the experiments of the inventors, the more the content of non-magnetic ceramic particles increases, the higher the self-resonant frequency shifts, and the better the frequency characteristics of the impedance. Furthermore, if the content of non-magnetic ceramic particles exceeds 90 parts by weight, the frequency characteristics of the impedance improve, but the formability of the magnetic material tends to deteriorate. Therefore, it is desirable that the content of non-magnetic ceramic particles is 90 parts by weight or less relative to 100 parts by weight of the soft magnetic metal particles.

[0020] Preferably, the sphericity of the non-magnetic ceramic particles is less than 0.98. According to experiments conducted by the inventors, the lower the sphericity of the non-magnetic ceramic particles, the more likely the DC superposition characteristics and frequency characteristics of the impedance are to improve. Furthermore, by using non-magnetic ceramic particles with a sphericity below a predetermined value, the strength of the magnetic core constructed from the composite magnetic material of the present invention is increased.

[0021] Preferably, the relative permittivity of the non-magnetic ceramic particles is 10 or less. By using such non-magnetic ceramic particles, the frequency characteristics of the impedance are further improved.

[0022] The composite magnetic material of this invention can be applied to various electronic components such as inductors, transformers, reactors, choke coils, composite elements (e.g., LC composite components that combine coil and capacitor regions), noise filters, magnetic sensors, and antennas. In this invention, electronic components using the composite magnetic material can have the following structures.

[0023] That is, the electronic component of the present invention has the aforementioned composite magnetic body, in which the non-magnetic ceramic particles are present between the soft magnetic metal particles on the cross-section of the composite magnetic body. The electronic component with such a structure exhibits excellent DC superposition characteristics and good frequency impedance characteristics. Therefore, the electronic component of the present invention can be suitably used as an electronic component for high-frequency applications.

[0024] Furthermore, on the cross-section of the composite magnetic body, if the area ratio occupied by the soft magnetic metal particles is set as A... M Let A be the area ratio outside the region occupied by the soft magnetic metal particles. C Therefore, A is preferred. C / A M The values ​​range from 0.07 to 19.3.

[0025] Furthermore, in the above, the area occupied by non-magnetic ceramic particles is included in area ratio A. C In the middle. Through area ratio A C / A M Within the aforementioned range, the DC superposition characteristics and the frequency characteristics of the impedance are further improved. Attached Figure Description

[0026] Figure 1 This is an internal transparent perspective view of an electronic component according to one embodiment of the present invention.

[0027] Figure 2 It means Figure 1 A rough cross-sectional view of the composite magnetic material contained in the electronic component shown.

[0028] Figure 3A This is a schematic diagram showing the main part of the composite magnetic material in an enlarged form.

[0029] Figure 3B This is a schematic diagram showing the main part of the composite magnetic material in an enlarged form.

[0030] Figure 4 It is a graph that roughly represents the results of measuring the frequency characteristics of impedance.

[0031] Figure 5 It is a graph that roughly represents the results of measuring the DC superposition characteristics.

[0032] Symbol Explanation

[0033] 1. Multilayer Inductor

[0034] 2 body

[0035] 4. Magnetic layer

[0036] 40 Composite Magnetic Materials

[0037] 41 Soft magnetic metal particles

[0038] 42 Ceramic Particles

[0039] 43 Adhesives

[0040] 50 coil conductor

[0041] 5 Internal electrode layer

[0042] 6. Lead-out electrodes

[0043] 3-terminal electrode Detailed Implementation

[0044] Hereinafter, the present invention will be described in detail based on the embodiments shown in the accompanying drawings. Furthermore, in this embodiment, a multilayer inductor will be described as an example of an electronic component of the present invention.

[0045] like Figure 1 As shown, the multilayer inductor 1 of this embodiment has a body 2 and terminal electrodes 3. The body 2 is composed of a magnetic layer 4 and a coil conductor 50 having a three-dimensional and helical shape, and the coil conductor 50 is embedded inside the body 2. A pair of terminal electrodes 3 are formed at both ends of the body 2, and the terminal electrodes 3 are electrically connected to the coil conductor 50 via lead-out electrodes 6.

[0046] The shape of the base body 2 is not particularly limited, but it is usually set to a cuboid shape. Furthermore, the size of the base body 2 is not particularly limited; it can be set to an appropriate size according to the application. The pair of terminal electrodes 3 also only need to be conductive, and their material or thickness is not particularly limited. For example, the terminal electrodes 3 can be sintered electrodes of conductive paste, resin electrodes containing thermosetting resin, or laminated electrodes with plating applied to the outer surface of the sintered electrode or resin electrode.

[0047] The coil conductor 50 contained in the body 2 has a spiral coil shape. This coil shape is formed by stacking internal electrode layers 5 with a predetermined pattern such as a square ring or a square semi-ring through a magnetic layer 4 along the Y-axis, and connecting adjacent internal electrode layers 5 with through-hole electrodes (not shown) or stepped electrodes. Furthermore, lead-out electrodes 6 are connected to both ends of the coil conductor 50 in the Y-axis direction. These lead-out electrodes 6 are through-hole electrodes that penetrate the magnetic layer 4. The materials of the coil conductor 50 and the lead-out electrodes 6 are only required to be conductive and are not particularly limited. For example, the coil conductor 50 and the lead-out electrodes 6 can be constructed with Ag (silver), Cu (copper), Au (gold), Al (aluminum), Ag alloys, Cu alloys, etc., as the main components. In addition, they may also contain glass frit, secondary components, and unavoidable impurities.

[0048] Furthermore, in this embodiment, the stacking direction of the magnetic layer 4 and the internal electrode layer 5 is aligned along the Y-axis, and the end face of the terminal electrode 3 is parallel to the X-axis and Z-axis. Additionally, the winding axis of the coil conductor 50 is aligned with the Y-axis. The X-axis, Y-axis, and Z-axis are perpendicular to each other.

[0049] The magnetic layer 4 of the base body 2 is composed of the composite magnetic body 40 of this embodiment. For example... Figure 2As shown, the composite magnetic body 40 includes soft magnetic metal particles 41 and ceramic particles 42. The details of the composite magnetic body 40 of this embodiment will be described below.

[0050] In this embodiment, the soft magnetic metal particles 41 can be made of a material exhibiting soft magnetism, and their composition is not particularly limited. Examples of materials exhibiting soft magnetism include pure iron, Fe-Si alloys (iron-silicon), Fe-Al alloys (iron-aluminum), Fe-Ni alloys (iron-nickel), Fe-Si-Al alloys (Fe-Si-Al), Fe-Si-Cr alloys (iron-silicon-chromium), Fe-Si-Al-Ni alloys, Fe-Ni-Si-Co alloys, Fe-Ni-Si-Co-Cr alloys, Fe amorphous alloys, and Fe nanocrystalline alloys. Furthermore, these soft magnetic metal particles 41 may also contain phosphorus (P).

[0051] Furthermore, the soft magnetic metal particles 41 can be composed entirely of the same material, or they can be a mixture of particles of different materials. For example, some of the soft magnetic metal particles 41 may be composed of pure iron particles, while others may be composed of Fe-Si alloys, etc. Examples of different materials include cases where the constituent elements of the metal particles are different, cases where the constituent elements are the same but their composition ratios are different, and cases where the crystal systems are different.

[0052] Alternatively, an insulating coating (not shown) can be formed on the surface of the soft magnetic metal particles 41. Examples of insulating coatings include resin coatings, inorganic insulating coatings, and coatings combining these, with inorganic insulating coatings being preferred. Examples of inorganic insulating coatings include oxide coatings formed by oxidizing the particle surface through heat treatment, phosphate coatings, Si-containing coatings formed by silane coupling treatment, and various glass coatings such as borosilicate glass. Furthermore, the insulating coating can be formed on all particles or only on a portion of the particles. The thickness of the insulating coating is not particularly limited; for example, it can be set to 5 nm to 60 nm. By forming an insulating coating, the insulation between metal particles can be improved, thereby increasing the dielectric strength of the multilayer inductor 1.

[0053] The median diameter (D50) of the soft magnetic metal particles 41 is preferably 1 μm or more and 15 μm or less, more preferably 1 μm or more and less than 5.0 μm. It is possible to observe the particles using a scanning electron microscope (SEM) or a scanning transmission electron microscope (STEM). Figure 2The cross-section of the substrate 2 (the cross-section of the magnetic layer 4) is shown, and image analysis is performed on the obtained cross-sectional photographs to determine the particle size of the soft magnetic metal particles 41. During this determination, cross-sectional photographs are taken with at least 5 fields of view. Furthermore, the equivalent circular diameter of the constituent particles (metal particles 41) contained in each cross-sectional photograph is measured to obtain the particle size distribution of the soft magnetic metal particles 41.

[0054] Furthermore, the soft magnetic metal particles 41 can also be formed by mixing two or more particle groups with different average particle sizes. In this case, the particle size distribution of the soft magnetic metal particles 41 shows two or more peaks depending on the number of mixed particle groups. In addition, the shape of the soft magnetic metal particles 41 is not particularly limited, and can be, for example, spherical, ellipsoidal, needle-like, scale-like, or irregular in shape.

[0055] On the other hand, the ceramic particles 42 are composed of non-magnetic ceramics with a particle size smaller than that of the soft magnetic metal particles 41.

[0056] Specifically, the median diameter (D50) of the ceramic particles 42 can be set to be 0.01 μm or more and 3.0 μm or less, preferably 0.05 μm to 2.0 μm, and more preferably 0.1 μm to 0.7 μm. Furthermore, the median diameter d of the ceramic particles 42... C The median diameter d of the soft magnetic metal particle 41 M The ratio (d) C / d M The value can be set to 0.003 to 0.8, preferably 0.01 to 0.67, and more preferably 0.03 to 0.25. Furthermore, the particle size of the ceramic particles 42 is the same as that of the soft magnetic metal particles 41, and can be measured by image analysis of the cross-sectional photograph.

[0057] Examples of main components of the ceramic particles 42 having the characteristics described above include silicate compounds, titanate compounds, stannate compounds, germanates, etc. Soft ferrites such as Mn-Zn ferrites or Mn-Ni ferrites are types of ceramics, but they are magnetic. Therefore, soft ferrites do not conform to the ceramic particles 42 of this embodiment. The ceramic particles 42 are not magnetic like ferrites, but rather non-magnetic.

[0058] Furthermore, the titanate compounds exemplified above are also a type of non-magnetic ceramic. These titanate compounds contain perovskite oxides with high relative permittivity, such as barium titanate or calcium titanate. However, as the ceramic particles 42 in this embodiment, compounds with a relative permittivity of 10 or less are preferred over compounds with high relative permittivity. By using ceramic particles 42 with low relative permittivity, the relative permittivity of the composite magnetic material 40 can also be reduced.

[0059] More specifically, the ceramic particles 42 are preferably silicate compounds containing one or more elements selected from copper (Cu), zinc (Zn), nickel (Ni), aluminum (Al), magnesium (Mg), and tin (Sn). Furthermore, among these silicate compounds, silicate compounds represented by the general formula α(βZnO·(1-β)CuO)·SiO2 are particularly preferred. In this formula, α is preferably 1.5 to 2.4. Additionally, β is preferably 0.60 to 1.00, more preferably 0.80 to 1.00.

[0060] By using the silicate compound described above as the material for the ceramic particles 42, it is possible to suppress the formation of a reaction phase that hinders the properties of the composite magnetic body 40 between the soft magnetic metal particles 41 and the ceramic particles 42. For example, when particles composed solely of nickel oxide (NiO) are used as the ceramic particles 42, Ni-containing ferrites sometimes form between the soft magnetic metal particles 41 and the ceramic particles 42. In contrast, when the silicate compound described above is used as the ceramic particles 42, no reaction phases such as ferrites are formed, and the DC superposition characteristics are better compared to the case where particles composed solely of nickel oxide are used.

[0061] In the cross-section of the composite magnetic body 40 of this embodiment (i.e., the cross-section of the magnetic body layer 4 constituting the substrate 2), ceramic particles 42 exist between the soft magnetic metal particles 41, i.e., grain boundaries 10, and fill the grain boundaries 10. Particularly preferred is... Figure 3A As shown, ceramic particles 42 exist at the triangular grain boundary 10a where three soft magnetic metal particles 42 are associated at a single point, and also exist not only at the triangular grain boundary 10a, but also at grain boundaries 10b outside the triangular grain boundary. In order to set the ceramic particles on the cross-section of the composite magnetic body 40 to the configuration described above, it is desirable to control the content of ceramic particles 42 and / or the roundness of ceramic particles 42 within a specified range.

[0062] Specifically, the content of ceramic particles 42 in the composite magnetic body 40 is preferably 0.6 parts by weight or more and 90 parts by weight or less relative to 100 parts by weight of soft magnetic metal particles, more preferably 1 part by weight or more and 70 parts by weight or less, and even more preferably 2 parts by weight or more and 60 parts by weight or less.

[0063] Furthermore, the roundness of the ceramic particles 42 is preferably lower than 0.98, and the ceramic particles 42 preferably have a shape with low roundness. In addition, the lower limit of roundness can be set to 0.50 or higher. More preferably, the roundness of the ceramic particles 42 is 0.55 to 0.85, and even more preferably 0.55 to 0.70.

[0064] Figure 3A and Figure 3BThis is a schematic diagram illustrating the influence of the content of ceramic particles 42 in the composite magnetic body 40 and the influence of the roundness of the ceramic particles 42. For example... Figure 3B As shown, when the content of ceramic particles 42 is low or the sphericity of ceramic particles 42 is high, ceramic particles 42 tend to concentrate at the triangular grain boundary 10a, exhibiting a tendency to aggregate at the triangular grain boundary 10a. On the other hand, as... Figure 3A As shown, when the content of ceramic particles 42 and / or the roundness of ceramic particles 42 are controlled within the above-mentioned specified range, ceramic particles 42 not only fill the three-way grain boundary 10a, but also fill the grain boundary 10b outside the three-way grain boundary, and the grain boundary 10 of the soft magnetic metal particles 41 tends to widen.

[0065] The widening of the grain boundaries 10 of the soft magnetic metal particles 41 is synonymous with the widening of the interparticle distance of the soft magnetic metal particles 41. By widening the interparticle distance of the soft magnetic metal particles 41, the relative permittivity of the composite magnetic body 40 tends to decrease, resulting in higher impedance even at high frequencies above 1 GHz. Furthermore, by using ceramic particles 42 with low sphericity, the strength of the base body 2 composed of the composite magnetic body 40 is improved. The reason for this improved strength is that an anchoring effect is achieved by denser filling of the ceramic particles 42 within the grain boundaries 10 of the soft magnetic metal particles 41.

[0066] Furthermore, the content of ceramic particles 42 and the roundness of ceramic particles 42 can both be determined by image analysis of the cross-section of the composite magnetic body 40 (in this embodiment, the cross-section of the magnetic body layer 4 constituting the base body 2).

[0067] For example, when observing the cross-section of the composite magnetic body 40 using backscattered electron images from SEM or HAADF images from STEM, the soft magnetic metal particles 41 can be identified as regions with high contrast, while the ceramic particles 42 can be identified as regions with lower contrast and denser particle size compared to the soft magnetic metal particles 41. In image analysis, based on the contrast, the area proportion A of the soft magnetic metal particles 41 on the observed cross-section is calculated. M And the proportion of the area outside the region occupied by the soft magnetic metal particles 41 on the observation section A C (i.e., the area of ​​the observation region A = A) M +A C Furthermore, in area ratio A C The area may include the ceramic particles 42, and also the area of ​​other voids or binders. The content of ceramic particles 42 can be determined by the area ratio A. M A C Convert to weight ratio for a rough estimate.

[0068] Furthermore, when the proportion of ceramic particles 42 in the composite magnetic body 40 is expressed by area ratio conversion, the area ratio A C Relative to area ratio A M The ratio (A) C / A M The preferred value is 0.07 to 19.3, more preferably 0.09 to 6.5, and even more preferably 0.094 to 3.7. Furthermore, the content and area ratio (AC / AM) of the ceramic particles 42 are preferably determined by image analysis performed on at least three cross-sections with different fields of view, as described above, and the average value is calculated. In determining the area ratios AM and AC, the magnification can be appropriately adjusted according to the particle size of the soft magnetic metal particles 41; for example, the observation field of view can be set to 10 μm square to 100 μm square.

[0069] In addition, in determining the roundness of ceramic particles 42, the magnification of SEM or STEM was set to approximately 10,000 to 50,000 times, and the field of view was set to a range equivalent to 1 μm square to 100 μm square. Cross-sectional photographs were taken from at least five fields of view. Furthermore, the roundness of each ceramic particle 42 contained in the captured cross-sectional photographs was determined by image analysis, and the average value was calculated.

[0070] In addition, bismuth oxide, boron oxide, glass components, etc., can be added as by-products to the ceramic particles 42. Furthermore, a coating layer such as a glass coating or an oxide film can be formed on the surface of the ceramic particles 42. If a coating layer is formed on the ceramic particles 42, it is expected to suppress the chemical reaction between the soft magnetic metal particles 41 and the ceramic particles 42, improve the insulation between the metal particles, and increase the sintering density of the composite magnetic body 40. However, forming a coating layer on the surface of the ceramic particles 42 increases the number of steps in the manufacturing process and reduces productivity. In this embodiment, although a coating layer is not formed on the surface of the ceramic particles 42, by setting the material or content of the ceramic particles 42 and their roundness as appropriate as described above, it is sufficient to ensure the suppression of the reactive phase, the improvement of insulation, and the increase of density. Therefore, in the composite magnetic body 40 of this embodiment, it is not necessarily necessary to form a coating layer on the surface of the ceramic particles 42.

[0071] In addition to the soft magnetic metal particles 41 and ceramic particles 42 described above, the composite magnetic body 40 of this embodiment may also include an adhesive 43. The type of adhesive 43 is not particularly limited, but resin is preferred. Specifically, examples of resins include epoxy resin, phenolic resin, acrylic resin, polyimide, polyamide-imide, silicone resin, and composite resins that are mixtures of the above resins. Furthermore, the content of adhesive 43 is preferably set to 1 to 2 parts by weight relative to 100 parts by weight of soft magnetic metal particles. By including adhesive 43 in the composite magnetic body 40, the insulation between the soft magnetic metal particles is further improved, and the strength of the base body 2 formed by the composite magnetic body 40 is increased.

[0072] Hereinafter, an example of a method for manufacturing the composite magnetic body 40 and the multilayer inductor 1 according to this embodiment will be described. However, the method for manufacturing the composite magnetic body 40 and the multilayer inductor 1 according to this embodiment is not limited to the method described below.

[0073] First, raw material powders for the soft magnetic metal particles 41 constituting the composite magnetic body 40 and raw material powders for the ceramic particles 42 are prepared. The raw material powders for the soft magnetic metal particles 41 can be produced using known powder manufacturing methods. These methods include, for example, gas atomization, water atomization, rotary disc method, and carbonyl method. Alternatively, they can be produced by mechanically pulverizing a thin strip obtained by a single-roller method. Furthermore, after obtaining the raw material powders for the soft magnetic metal particles 41 using the above methods, the particle size of the soft magnetic metal particles 41 can be adjusted by sieving or air classifying. Additionally, if an insulating coating is to be formed on the surface of the soft magnetic metal particles 41, the raw material powder obtained above can be appropriately subjected to coating formation treatments such as heat treatment, phosphate treatment, silane coupling treatment, or hydrothermal synthesis.

[0074] On the other hand, ceramic particles 42 can be made from ceramic powder produced by a known powder manufacturing method. For example, a raw material powder of a silicate compound represented by the general formula α(βZnO·(1-β)CuO)·SiO2 can be obtained by calcining powders of silicon oxide, zinc oxide, and copper oxide in a desired ratio. In this case, the particle size of ceramic particles 42 can be adjusted by pulverizing and appropriately classifying the raw material powder. Furthermore, the sphericity of ceramic particles 42 can be adjusted by controlling the type of pulverizing apparatus or pulverizing conditions used during pulverization, and can also be adjusted by subjecting the pulverized particles to plasma treatment.

[0075] Next, the method for manufacturing the multilayer inductor 1 using the aforementioned raw material powder and the sheet method will be described. First, a magnetic paste is obtained by mixing and slurrying the raw material powders of soft magnetic metal particles 41 and ceramic particles 42 with additives such as solvents or binders 43. As the magnetic paste added at this time, solvents such as acetone, isopropanol (IPA), methyl ethyl ketone (MEK), butyl diethylene glycol acetate (BCA), and methanol can be used. Alternatively, a dispersant can be added to the magnetic paste; dispersants such as silane coupling agents, oleic acid, and oleylamine can be used.

[0076] Furthermore, the magnetic paste is thinned using a scraper method or similar technique, and after firing, a green sheet is obtained, which becomes the magnetic layer 4. Next, a conductive paste is printed onto the formed green sheet according to a predetermined pattern, and after firing, an internal electrode pattern is formed, which becomes the internal electrode layer 5. Moreover, by stacking multiple green sheets with printed internal electrode patterns and applying appropriate pressure and cutting, a green laminate is obtained. At this time, during or after stacking the green sheets, through-hole electrodes are formed between adjacent internal electrode patterns in the stacking direction, and the internal electrode patterns are joined together. By forming through-hole electrodes, a three-dimensional and spiral coil conductor pattern is integrally formed inside the green laminate. In addition, the lead-out electrode 6 can also be formed as a through-hole electrode in the same manner as described above.

[0077] Next, the green laminate obtained by the above-described process is fired to obtain body 2. There are no particular restrictions on the firing conditions; for example, the holding temperature during firing can be set to 550°C to 850°C, and the holding time during firing can be set to 0.5 to 3.0 hours. Furthermore, a binder removal treatment can be appropriately performed before the firing process.

[0078] Furthermore, by forming a pair of terminal electrodes 3 on the substrate 2 obtained by the above-described process, a result is obtained. Figure 1 The multilayer inductor 1 shown.

[0079] (Summary of Implementation Methods)

[0080] In the multilayer inductor 1 of this embodiment, the magnetic layer 4, which corresponds to the core portion of the base 2, is composed of a composite magnetic material 40 containing soft magnetic metal particles 41 and ceramic particles 42. Furthermore, the ceramic particles 42 contained in this composite magnetic material 40 are characterized by being non-magnetic ceramics with a median diameter (D50) smaller than that of the soft magnetic metal particles 41. By including ceramic particles 42 with the characteristics described above, the composite magnetic material 40 and the multilayer inductor 1 of this embodiment improve the DC superposition characteristics and the frequency characteristics of the impedance compared to conventional methods.

[0081] Figure 4This is a graph that roughly represents the frequency characteristics of the impedance (|Z|) measured for a multilayer inductor. Figure 4 In the graph, the solid line represents the result when the magnetic body is composed solely of soft magnetic metal particles 41 without the addition of ceramic particles 42. On the other hand, in... Figure 4 The graph Ex1, shown by the dashed line, represents the results when ceramic 42 is added to the composite magnetic body 40. (See graph for example.) Figure 4 As shown, if ceramic particles 42 are added, the peak (maximum) of the impedance shifts towards the high-frequency side. That is, by adding ceramic particles 42 with specified characteristics to the composite magnetic body 40, the self-resonant frequency of the multilayer inductor 1 shifts towards the high-frequency side and can be set to above 1 GHz.

[0082] in addition, Figure 5 This is a graph that roughly represents the results of evaluating the DC superposition characteristics of a multilayer inductor. In this embodiment, the DC superposition characteristics are evaluated based on the rate of change of inductance when a DC current is applied. Specifically, the inductance L0 in the state without a DC current and the inductance L in the state with a DC current applied are measured, and their rate of change is calculated as (L-L0) / L0(%). It can be said that the smaller the rate of change of inductance, the better the DC superposition characteristics. Figure 4 same, Figure 5 The solid line graph Cex represents the result when the magnetic body is composed solely of soft magnetic metal particles 41 without the addition of ceramic particles 42, while the dashed line graph Ex1 represents the result when ceramic particles 42 are included. Figure 5 As shown, by adding ceramic particles 42 with specified properties to the composite magnetic body 40, the rate of change of inductance when a DC current is applied is reduced, and the DC superposition characteristics are improved.

[0083] Furthermore, the reason for the improvement in DC superposition characteristics or frequency characteristics of impedance is not necessarily clear. It is thought that, for example, the effect is caused by the widening of the interparticle distance of the soft magnetic metal particles 41 due to the addition of ceramic particles 42.

[0084] In the composite magnetic body 40 of this embodiment, the content of ceramic particles 42 is 0.6 parts by weight or more and 90 parts by weight or less relative to 100 parts by weight of soft magnetic metal particles. If the content of ceramic particles 42 is increased, then... Figure 4 As shown in Figure Ex2, the self-resonant frequency shifts further towards higher frequencies, and the frequency characteristics of the impedance are further improved. Additionally, as... Figure 5 As shown in Figure Ex2, the DC superposition characteristics are further improved. Furthermore, if the content of ceramic particles 42 exceeds 90 parts by weight, the frequency characteristics of the impedance improve, but the formability of the composite magnetic body 40 tends to deteriorate. Therefore, it is desirable that the content of ceramic particles 42 is less than 90 parts by weight relative to the soft magnetic metal particles.

[0085] Furthermore, in the composite magnetic material 40 of this embodiment, the sphericity of the ceramic particles 42 is less than 0.98. By using particles with low sphericity as the ceramic particles 42, such as... Figure 4 and Figure 5 As shown in Figure Ex2, the DC superposition characteristics and the frequency characteristics of the impedance show a further improvement trend. Furthermore, as mentioned above, by using ceramic particles 42 with low sphericity, an anchoring effect can be obtained, increasing the strength of the base body 2 composed of the composite magnetic body 40.

[0086] Furthermore, in this embodiment, the relative permittivity of the ceramic particles 42 is preferably 10 or less. By using ceramic particles 42 with low relative permittivity, the relative permittivity of the composite magnetic body 40 also tends to decrease, and the frequency characteristics of the impedance are further improved.

[0087] More specifically, the ceramic particles 42 are preferably silicate compounds that meet specified conditions. By using a silicate compound as the ceramic particles 42, it is possible to suppress the formation of a reaction phase between the soft magnetic metal particles 41 and the ceramic particles 42 that hinders the properties of the composite magnetic body 40.

[0088] The embodiments of the present invention have been described above, but the present invention is not limited to the above embodiments, and various changes can be made within the scope of the present invention.

[0089] For example, in the above embodiments, a multilayer inductor was described as an application example of the composite magnetic material 40 of the present invention, but the inductors to which the present invention can be applied are not limited to multilayer types. For example, the composite magnetic material 40 can be press-formed to produce a magnetic core, and conductive wires or plates can be wound on the magnetic core to form an inductor element. Alternatively, the composite magnetic material of the present invention can be pressed together with an air-core coil to form an inductor element. In the case of these wound inductors, the type of magnetic core is not particularly limited, and it can be a toroidal, FT, ET, EI, UU, EE, EER, UI, drum, pot, cup, or other pressed or sintered material. In addition, the composite magnetic material 40 of the present invention can also be applied to the magnetic core of thin-film inductors.

[0090] Furthermore, in the above embodiments, an inductor is exemplified as an electronic component of the present invention, but the electronic component of the present invention is not limited to this; it can also be a transformer, reactor, choke coil, composite element (e.g., an LC composite component combining a coil region and a capacitor region), noise filter, magnetic sensor, antenna, contactless power supply device, and other electronic components. That is, the composite magnetic body 40 of the present invention can be used as a magnetic core in various coil devices or as a magnetic sheet in filters, antennas, magnetic sensors, etc. When the various electronic components described above include the composite magnetic body 40 of the present invention, the electronic component can also be suitably used for high-frequency applications.

[0091] Example

[0092] The present invention will be further described below based on detailed embodiments, but the present invention is not limited to these embodiments.

[0093] Experiment 1

[0094] In Experiment 1, magnetic specimens consisting solely of metal particles (Specimen 1) and magnetic specimens consisting of a mixture of metal and ceramic particles (Specimens 4-13) were prepared, and the characteristics of each magnetic specimen were evaluated. Additionally, in Experiment 1, experiments were conducted in Specimens 4-13 with variations in the type of ceramic particles. The method for preparing the magnetic specimens is described below.

[0095] First, 94.0Fe-6.0Si alloy powder was prepared as the metal raw material powder for the soft magnetic metal particles 41. This metal raw material powder was produced by atomization, and then an oxide coating with an average thickness of 20 nm was formed on the surface of the metal particles by heat treatment.

[0096] On the other hand, the specified oxide powder is mixed, calcined, and then pulverized to produce ceramic raw material powder for ceramic particles 42. As described above, in Experiment 1, ceramic raw material powders of different materials were prepared in samples 4 to 13. Table 1 shows the composition of ceramic particles 42 in each sample and the relative permittivity of the ceramic particles 42.

[0097] Furthermore, the relative permittivity of ceramic particles 42 was determined by volumetric method using an LCR meter (4285A). The measurement frequency was set to 1 MHz, and the measurement was performed at room temperature (25°C). Additionally, a test sample for the relative permittivity was obtained by pressing only the raw material powder of ceramic particles 42 obtained in the above-described process. The test sample was made into a disc shape with a diameter of 10 mm and a height of 5 mm.

[0098] Next, the raw material powder of the prepared soft magnetic metal particles 41 and the raw material powder of the ceramic particles 42 are mixed to obtain a magnetic material sample. However, in sample 1, no ceramic particles 42 are added, and the magnetic material sample consists only of soft magnetic metal particles 41. Furthermore, in all magnetic material samples of Experiment 1, the particle size (D50) of the soft magnetic metal particles 41 is set to 3.0 μm. In addition, in each magnetic material sample of Experiment 1, the particle size (D50) of the ceramic particles 42 is set to 0.3 μm, and the content of ceramic particles 42 is set to 2.0 parts by weight relative to 100 parts by weight of soft magnetic metal particles.

[0099] (Determination of the relative permittivity of magnetic samples)

[0100] In the magnetic material samples obtained in the above-described process, the relative permittivity was also measured in the same manner as that of the raw material powder of ceramic particles 42. In the determination of the relative permittivity of the magnetic material samples, a mixed powder of soft magnetic metal particles 41 and ceramic particles 42 was press-formed into a disc-shaped molded body, which was then used as the test sample. Preferably, the relative permittivity value of the magnetic material sample is low, with values ​​below 100 considered good. The results of measuring the relative permittivity of each magnetic material sample are shown in Table 1.

[0101] (Preparation of multilayer inductor prototypes)

[0102] In addition, in Experiment 1, inductor samples were fabricated using the prepared magnetic material samples. Specifically, butyraldehyde resin and solvent were added to the aforementioned magnetic material samples to obtain a magnetic material paste. Using this magnetic material paste, inductor samples were fabricated using the sheet method. Figure 1 The layered inductor shown. Furthermore, in the inductor sample, the coil conductor contained within the body 2 is composed of Ag electrodes.

[0103] (Determination of the frequency characteristics of impedance)

[0104] The frequency characteristics of the impedance were measured using an impedance analyzer (E4991A RF impedance / material analyzer) to evaluate the performance of the inductor samples. Measurements were performed at room temperature, and the self-resonant frequency (SRF) was calculated from the maximum impedance value. If the SRF is above 1000 MHz, the multilayer inductor can be adequately used for high-frequency applications. Therefore, an SRF above 1000 MHz is considered good. The evaluation results of the frequency characteristics for each sample are shown in Table 1.

[0105] (Evaluation of DC superposition characteristics)

[0106] Next, the DC superposition characteristics of the inductor sample were measured. The DC superposition characteristics were evaluated based on the rate of change of inductance when a DC current was applied to the inductor sample. In this embodiment, an LCR meter (4284A precision LCR meter) was used to measure the inductance L0 in the state without a DC current (Idc) and the inductance L1 in the state with a DC current of 1.5A. 1.5 Then, based on equation (L) 1.5 The rate of change of inductance (ΔL / L0) is calculated as ΔL / L0 (in %). A smaller rate of change of inductance indicates better DC superposition characteristics. In this experiment, a rate of change of 0% for the inductance is considered good. Table 1 shows the evaluation results of the frequency characteristics for each sample.

[0107] Table 1

[0108]

[0109] (Evaluation results of Experiment 1)

[0110] As shown in Table 1, among samples 4–13 with added ceramic particles, the SRF was higher and the rate of change of inductance was lower compared to sample 1 without added ceramic particles. This result confirms that adding non-magnetic ceramic particles with a particle size finer than soft magnetic metal particles to the composite magnetic material improves the DC superposition characteristics and the frequency characteristics of the impedance. Furthermore, sample 5, containing ZnO·Fe2O3, is a type of ferrite, but it is a non-magnetic ceramic.

[0111] Furthermore, comparing the results of samples 4 to 13, it is evident that the inductor characteristics are particularly good in samples 6 to 13, which contain silicate compounds. Specifically, the results are as follows: in samples 6 to 13, the SRF is above 1000 MHz, and the inductance variation rate is 0%. Compared to samples 4 and 5, the DC superposition characteristic or the frequency characteristic of the impedance is further improved. The relative permittivity of the silicate compounds in samples 6 to 13 is 10 or less. Based on the results of these samples 6 to 13, it can be confirmed that the relative permittivity of the ceramic particles added to the composite magnetic material is preferably 10 or less.

[0112] Furthermore, among the samples 6 to 13 containing silicate compounds, samples 6 to 8 received a good evaluation result. Based on this result, it can be confirmed that, among the silicate compounds, silicate compounds represented by the general formula α(βZnO·(1-β)CuO)·SiO2 are particularly preferred as ceramic particles.

[0113] Furthermore, although not listed in Table 1, samples with only NiO composite magnetic material added were also prepared as ceramic particles. In the NiO-only samples, cross-sectional observations based on SEM confirmed the formation of Ni ferrite between the soft magnetic metal particles and the ceramic particles. On the other hand, in samples 6–13 with added silicate compounds, no reactive phase like Ni ferrite was observed. Moreover, samples 6–13 with added silicate compounds exhibited higher SRF and better DC superposition characteristics compared to the NiO-only samples. These results confirm that by using silicate compounds as ceramic particles, the formation of reactive phases that hinder the properties of the magnetic material can be suppressed, and the DC superposition characteristics or frequency characteristics of the impedance are further improved.

[0114] Experiment 2

[0115] In Experiment 2, the particle size (D50) of the soft magnetic metal particles 41 and the particle size (D50) of the ceramic particles 42 were varied to prepare magnetic samples 21-32. Furthermore, using these magnetic samples, samples were prepared in the same manner as in Experiment 1. Figure 1The stacked inductors shown were used to obtain inductor samples 21 to 32. Table 2 shows the particle size of the soft magnetic metal particles 41 and the particle size of the ceramic particles 42 in each sample of Experiment 2.

[0116] Furthermore, the particle sizes of particles 41 and 42 shown in Table 2 were calculated by observing the cross-section of the fabricated inductor sample using SEM and performing image analysis. Cross-sectional observations were conducted in five fields of view, and the equivalent circle diameter of each particle 41 and 42 contained within the observed field of view was measured, thereby obtaining the particle size distribution of each particle 41 and 42. The particle sizes shown in other tables besides Table 2 are the same as described above.

[0117] In addition, in each sample of Experiment 2, 94.0Fe-6.0Si alloy was used as soft magnetic metal particles 41, and 2ZnO·SiO2 was used as ceramic particles 42. Furthermore, in each sample of Experiment 2, the content of ceramic particles 42 was set to 2.0 parts by weight relative to 100 parts by weight of soft magnetic metal particles. The experimental conditions in Experiment 2, except as described above, were the same as in Experiment 1. The evaluation results for each sample of Experiment 2 are shown in Table 2.

[0118] Table 2

[0119]

[0120] (Evaluation results of Experiment 2)

[0121] As shown in Table 2, in samples 21–28 and 31–32, which contained ceramic particles with a particle size smaller than that of the soft magnetic metal particles, the SRF was higher and the rate of change of inductance was lower compared to sample 1, which did not contain ceramic particles. On the other hand, in samples with a particle size ratio d… C / d M In sample 29 (with a particle size of 1.0) and sample 30 (with ceramic particles larger than the soft magnetic metal particles), almost no improvement in DC superposition characteristics or impedance frequency characteristics was achieved. Based on these results, it can be confirmed that by adding ceramic particles with a particle size smaller than the soft magnetic metal particles to the composite magnetic material, both DC superposition characteristics and impedance frequency characteristics are improved.

[0122] Furthermore, in samples 22-28, the SRF was above 1000 MHz, and the rate of change of inductance was 0%. Based on this result, it can be confirmed that the particle size (D50) of the ceramic particles is preferably 0.05 μm to 2.0 μm, more preferably 0.1 μm to 0.7 μm. Additionally, it can be confirmed that the particle size ratio d... C / d M The preferred value is 0.01 to 0.67, and more preferably 0.03 to 0.25.

[0123] Furthermore, the results from samples 31 and 32 confirm that, even with changes in the particle size of the soft magnetic metal particles, the same improvement in DC superposition characteristics or impedance frequency characteristics can be achieved as with samples 22-28. Additionally, sample 31 exhibits a higher SRF compared to sample 32. These results indicate that by adding ceramic particles and further reducing the particle size of the soft magnetic metal particles, the impedance frequency characteristics can be further improved.

[0124] Experiment 3

[0125] In Experiment 3, to investigate the effect of ceramic particle content, magnetic samples were prepared by varying the ceramic particle content, and inductor samples 41–58 were also prepared. Table 3 shows the ceramic particle content in each of the samples 41–58 from Experiment 3.

[0126] In addition, in Experiment 3, besides measuring the DC superposition characteristics or the frequency characteristics of the impedance, the area ratio of the soft magnetic metal particles and ceramic particles, as well as the inductance L, were also measured. Regarding the area ratio A... C / A M For the inductor sample, five field-of-view observations were performed on its cross-section, and the average value was used for calculation. Additionally, an impedance analyzer was used to measure the inductance L at a frequency of 100 MHz. Table 3 shows the evaluation results for each sample in Experiment 3.

[0127] In Experiment 3, 94.0Fe-6.0Si alloy with a D50 of 3.0 μm was used as the soft magnetic metal particles, and 2ZnO·SiO2 with a D50 of 0.3 μm was used as the ceramic particles. The experimental conditions in Experiment 3 were the same as in Experiment 1, except that the content of ceramic particles was changed.

[0128] Table 3

[0129]

[0130] (Evaluation results of Experiment 3)

[0131] As shown in Table 3, it can be confirmed that when the content of ceramic particles is 0.6 parts by weight or more per 100 parts by weight of soft magnetic metal particles, or when the area ratio A... C / A MWith a value of 0.072 or higher, the SRF is above 1000, and the DC superposition characteristics and frequency characteristics of the impedance are improved. Furthermore, it can be confirmed that the higher the ceramic particle content, the more the SRF shifts towards the high-frequency side, and the frequency characteristics of the impedance are further improved. Moreover, in samples 53-57 with a ceramic particle content of 50 parts by weight or more, the SRF is ">3000". The reason for this statement is that the measurable range of the impedance analyzer used in this experiment is up to 3000 MHz. It is assumed that the higher the ceramic particle content, the higher the SRF of samples 53-57.

[0132] Furthermore, in sample 58 with a ceramic particle content of 100 parts by weight, the DC superposition characteristics and frequency characteristics of impedance were considered to be improved. However, due to the excessive ceramic particle content, the formability of the magnetic sample deteriorated, and the shape of the raw body could not be maintained normally. Therefore, considering the formability of the magnetic body, the upper limit of the ceramic particle content is preferably set to 90 parts by weight or less, and the area ratio A C / A M The upper limit is preferably set to below 19.257.

[0133] Furthermore, considering the inductance L measurement results shown in Table 3, the content of ceramic particles is more preferably 1 part by weight or more and 70 parts by weight or less, and even more preferably 2 parts by weight or more and 60 parts by weight or less. Additionally, the area ratio AC / AM is more preferably 0.091 to 6.434, and even more preferably 0.094 to 3.670. That is, when the content of ceramic particles is within the above-mentioned range, good DC superposition characteristics and good frequency characteristics can be obtained while ensuring the necessary inductance L.

[0134] Experiment 4

[0135] In Experiment 4, magnetic samples were fabricated by varying the roundness of the ceramic particles, resulting in inductor samples 61-67. During the preparation of the raw material powder, the pulverization conditions after calcination (pulverization time in the ball mill, ball diameter, etc.) were adjusted, and the pulverized particles were appropriately subjected to plasma treatment to control the roundness of the ceramic particles. Furthermore, the roundness of the ceramic particles was calculated by observing the cross-section of the inductor samples using SEM and performing image analysis. Specifically, the magnification for cross-section observation was set to 35000x for 10μm particles. 2 Cross-sectional photographs were taken at five different fields of view. Image analysis was performed on the obtained cross-sectional photographs to determine the roundness of the ceramic particles contained within them. Table 4 shows the roundness of the ceramic particles in each sample of Experiment 4. Furthermore, the roundness values ​​shown in Table 4 are average values.

[0136] In addition, in Experiment 4, a cutting test was conducted to evaluate the strength of the fabricated inductor samples. In the cutting test, the inductor sample was first cut using a cutting machine along a direction parallel to the stacking direction of the magnetic layers (Y-axis direction). The cut cross-section was then observed with the naked eye and a stereomicroscope to confirm the presence or absence of cracks or notches. 1000 cutting tests were performed on each sample, and the proportion of good samples without cracks or notches was calculated.

[0137] Furthermore, in Experiment 4, 94.0Fe-6.0Si alloy with a D50 of 3.0 μm was used as the soft magnetic metal particles, and 2ZnO·SiO2 with a D50 of 0.3 μm was used as the ceramic particles, with the ceramic particle content set at 2 parts by weight. The experimental conditions in Experiment 3, except as described above, were the same as in Experiment 1. Table 4 shows the evaluation results for each sample in Experiment 4.

[0138] Table 4

[0139]

[0140] (Evaluation results of Experiment 4)

[0141] As shown in Table 4, the results are as follows: In samples 62 to 67 with a ceramic particle sphericity of less than 0.98, the relative permittivity of the magnetic sample is less than 100, and the frequency characteristics of the impedance are improved. In particular, it can be confirmed that the sphericity of the ceramic particles is more preferably 0.55 to 0.85, and even more preferably 0.55 to 0.70.

[0142] Furthermore, the results in Table 4 confirm that reducing the roundness of the ceramic particles improves the yield rate and the strength of the substrate during the cutting test. However, in sample 67 with a ceramic particle roundness of 0.5, the yield rate during the cutting test actually decreased. Based on this result, it can be confirmed that the lower limit of the roundness of the ceramic particles is preferably set to 0.55 or higher.

Claims

1. A composite magnetic material, characterized in that, Include: Soft magnetic metal particles; and The non-magnetic ceramic particles have a particle size D50 smaller than that of the soft magnetic metal particles, and the content of the non-magnetic ceramic particles is more than 0.6 parts by weight and less than 90 parts by weight per 100 parts by weight of the soft magnetic metal particles. The non-magnetic ceramic particles have a sphericity of 0.55~0.

85. The non-magnetic ceramic particles are silicate compounds represented by the general formula α(βZnO·(1-β)CuO)·SiO2. In the general formula, α is 1.5 to 2.4, and β is 0.60 to 0.

80.

2. The composite magnetic material according to claim 1, characterized in that, The relative permittivity of the non-magnetic ceramic particles is below 10.

3. An electronic component, characterized in that, Having the composite magnetic body as described in claim 1 or 2, On the cross-section of the composite magnetic body, the non-magnetic ceramic particles exist between the soft magnetic metal particles.

4. The electronic component according to claim 3, characterized in that, On the cross-section of the composite magnetic body, let A be the area ratio occupied by the soft magnetic metal particles. M Let A be the area ratio outside the region occupied by the soft magnetic metal particles. C hour, A C / A M is 0.07 to 19.3.

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