Multilayer coil component

Abstract

To provide a multilayer coil component having excellent magnetic permeability and voltage resistance characteristics.SOLUTION: A multilayer coil component includes a magnetic layer, wherein the magnetic layer has a main phase made of spinel ferrite and a grain boundary phase containing silicon oxide and bismuth oxide, and the area ratio of the main phase to the grain boundary phase is 92:8 to 99:1.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a multilayer coil component. [Background technology]

[0002] In recent years, as ICT devices have become smaller, the ferrite chip bead products used have become smaller. Multilayer ferrite chip bead products require thinner layers between the internal electrode layers to achieve miniaturization, but if insulation between the layers is not achieved, short circuits will occur. Therefore, there is a need for designs that reduce the particle size of ferrite materials in order to reduce the size of voids that can become low-voltage areas and also reduce the porosity.

[0003] Patent Document 1 discloses a ferrite material that uses NiCuZn-based ferrite containing tin oxide and potassium oxide, which has excellent DC bias characteristics and can suppress the particle size after sintering to 1.3 μm. However, this particle size is too large for a material to be used between thin layers.

[0004] Patent Document 2 discloses a ferrite material with improved density and magnetic permeability by mixing the magnetic material and the non-magnetic material in a ratio of 20% by weight:80% by weight to 80% by weight:20% by weight. However, if the ratio of non-magnetic material increases, the magnetic path is interrupted, resulting in a material with low magnetic permeability. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-213578 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-220469 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a multilayer coil component having high magnetic permeability and excellent voltage resistance characteristics. [Means for solving the problem]

[0007] In order to achieve the above object, a multilayer coil component according to one aspect of the present invention comprises: A multilayer coil component having a magnetic layer, The magnetic layer has a main phase made of spinel ferrite and a grain boundary phase containing silicon oxide and bismuth oxide, and the area ratio of the main phase to the grain boundary phase is 92:8 to 99:1.

[0008] This laminated coil component has improved magnetic permeability and improved voltage resistance characteristics.

[0009] Preferably, the magnetic layer has a ferrite composition containing a main component and a subcomponent. Preferably, the main component contains 24.0 to 50.0 mol % (more preferably 26.0 to 49.8 mol %) of iron oxide (calculated as Fe2O3), 2.2 to 12.0 mol % (more preferably 5.0 to 10.0 mol %) of copper oxide (calculated as CuO), 12.3 to 39.0 mol % (more preferably 13.0 to 37.9 mol %) of zinc oxide (calculated as ZnO), and the remainder is nickel oxide. Preferably, the subcomponent contains 0.02 to 3.0 mol % (more preferably 0.10 to 2.0 mol %) of bismuth oxide (calculated as Bi2O3) by weight, relative to 100% by weight of the main component.

[0010] The secondary component may further contain silicon oxide, and the content is preferably 0.02 to 3.0 wt %, more preferably 0.1 to 3.0 wt %, and particularly preferably 0.1 to 2.0 wt % in terms of SiO2 relative to 100 wt % of the main component.

[0011] Cobalt oxide may be further contained as a secondary component, and is preferably contained in an amount of 0.1 to 4.0% by weight, more preferably 0.1 to 3.0% by weight, calculated as Co3O4, relative to 100% by weight of the main component.

[0012] Silver oxide may be further contained as a secondary component, and is preferably contained in an amount of 0.02 to 3.2 wt %, more preferably 0.02 to 3.0 wt %, or even 0.1 to 3.0 wt %, calculated as Ag2O relative to 100 wt % of the main component.

[0013] Preferably, the average particle size of the main phase is 0.27 to 0.6 μm, more preferably 0.27 to 0.5 μm. [Brief explanation of the drawings]

[0014] [Figure 1A] FIG. 1A is a perspective view showing the interior of a multilayer coil component according to one embodiment of the present invention. [Figure 1B] FIG. 1B is a perspective view showing the inside of a multilayer coil component according to another embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram of a cross-sectional SEM image of a magnetic layer of the multilayer coil component shown in FIG. 1A. [Figure 3] FIG. 3 is a photograph of element mapping by STEM-EDS of a cross section of a magnetic layer of a multilayer coil component according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] The following describes the embodiments.

[0016] As shown in FIG. 1A, a multilayer chip coil 1 as a multilayer coil component according to one embodiment of the present invention has a chip body 4 in which magnetic layers (ceramic layers) 2 and internal electrode layers 3 are alternately stacked in the Y-axis direction.

[0017] Each internal electrode layer 3 has a square ring, C-shape, or U-shape, and is spirally connected by a through-hole electrode (not shown) for connecting internal electrodes or a stepped electrode that penetrates adjacent magnetic layers 2, thereby forming a coil conductor 30.

[0018] Terminal electrodes 5, 5 are formed on both ends in the Y-axis direction of the chip body 4. Each terminal electrode 5 is connected to an end of a terminal connection through-hole electrode 6 that penetrates the laminated magnetic layers 2, and each terminal electrode 5, 5 is connected to both ends of a coil conductor 30 that constitutes a closed magnetic circuit coil (winding pattern).

[0019] In this embodiment, the stacking direction of the magnetic layers 2 and the internal electrode layers 3 coincides with the Y axis, and the end faces of the terminal electrodes 5, 5 are parallel to the X axis and Z axis. The X axis, Y axis, and Z axis are perpendicular to each other. In the multilayer chip coil 1 shown in FIG. 1A, the winding axis of the coil conductor 30 substantially coincides with the Y axis.

[0020] There are no particular restrictions on the external shape or dimensions of the chip body 4, and they can be set appropriately depending on the application. Typically, the external shape is approximately rectangular, with an X-axis dimension of 0.125 to 0.8 mm, a Y-axis dimension of 0.25 to 1.6 mm, and a Z-axis dimension of 0.1 to 1.0 mm.

[0021] Furthermore, there are no particular restrictions on the inter-electrode thickness and base thickness of the magnetic layer 2, and the inter-electrode thickness (the distance between the internal electrode layers 3, 3) can be set to about 2.5 to 50 μm, and the base thickness (the length of the terminal connection through-hole electrode 6 in the Y-axis direction) can be set to about 5 to 300 μm. However, in this embodiment, even if the inter-electrode thickness of the magnetic layer 2 is thinned to about 2.0 μm or less, a multilayer coil component with high magnetic permeability and excellent voltage resistance characteristics can be obtained.

[0022] In this embodiment, the terminal electrodes 5 are not particularly limited and are formed by applying a conductive paste containing Ag, Pd, or the like as a main component to the outer surface of the main body 4, baking the paste, and then electroplating the paste. Cu, Ni, Sn, or the like can be used for the electroplating.

[0023] The coil conductor 30 contains Ag (including Ag alloys), and is made of, for example, simple Ag, an Ag-Pd alloy, etc. The coil conductor may contain Zr, Fe, Mn, Ti, and oxides thereof as minor components.

[0024] The magnetic layer 2 is made of a ferrite composition containing a main component and a subcomponent. The ferrite composition will be described in detail below.

[0025] The main components include iron oxide, copper oxide, zinc oxide and nickel oxide.

[0026] The content of iron oxide in 100 mol% of the main component, calculated as Fe2O3, is preferably 24.0 mol% or more, more preferably 26.0 mol% or more, and preferably 50.0 mol% or less, more preferably 49.8 mol% or less. If the content of iron oxide is too low, the initial permeability tends to decrease. If the content of iron oxide is too high, the temperature characteristics of permeability tend to deteriorate.

[0027] The copper oxide content, calculated as CuO, of 100 mol% of the main component is preferably 2.2 mol% or more, more preferably 5.0 mol% or more, and preferably 12.0 mol% or less, and more preferably 10.0 mol% or less. If the copper oxide content is too low, the density decreases, the resistivity decreases, and the initial permeability also tends to decrease. This is thought to be due to poor sinterability. If the copper oxide content is too high, the initial permeability and resistivity tend to decrease. This is thought to be due to segregation of copper oxide.

[0028] The content of zinc oxide in 100 mol% of the main component, calculated as ZnO, is preferably 12.3 mol% or more, more preferably 13.0 mol% or more, and preferably 39.0 mol% or less, and more preferably 37.9 mol% or less. If the content of zinc oxide is too low, the resistivity and the withstand voltage characteristics (breakdown voltage value) tend to decrease. If the content of zinc oxide is too high, the resistivity and initial permeability tend to decrease.

[0029] The remainder of the main component is composed of nickel oxide. The content of nickel oxide in the main component is not particularly limited, but is, for example, 47.0 to 47.5 mol % in terms of NiO.

[0030] In addition to the above-mentioned main components, the magnetic layer 2 contains at least bismuth oxide and silicon oxide as secondary components.

[0031] The content of bismuth oxide, calculated as Bi2O3, is preferably 0.02 parts by weight or more, more preferably 0.10 parts by weight or more, and preferably 3.0 parts by weight or less, and more preferably 2.0 parts by weight or less, relative to 100 parts by weight of the main component. If the content of bismuth oxide is too low, the initial permeability and resistivity tend to decrease. This is thought to be due to poor sinterability. If the content of bismuth oxide is too high, the resistivity tends to decrease. This is thought to be due to abnormal grain growth of bismuth.

[0032] The content of silicon oxide, calculated as SiO2, is preferably 0.02 wt% or more, more preferably 0.10 wt% or more, relative to 100 parts by weight of the main component. It may be contained at 3.0 wt% or less, more preferably 2.30 wt% or less, or even 2.00 wt% or less. By including silicon oxide, the average particle size can be reduced and the resistivity and withstand voltage can be improved. However, if the silicon oxide content is too high, the density tends to decrease and the resistivity tends to decrease. This is thought to be due to poor sinterability.

[0033] Furthermore, the magnetic layer 2 may contain cobalt oxide in addition to the above components. The content of cobalt oxide is not particularly limited, but is preferably 0.1 wt % or more, preferably 4.0 wt % or less, and more preferably 3.0 wt % or less, calculated as Co3O4, relative to 100 parts by weight of the main component. The inclusion of cobalt oxide improves density, resistivity, and electrical durability. However, if the cobalt oxide content is too high, the density, initial permeability, and resistivity tend to decrease.

[0034] Furthermore, the magnetic layer 2 may contain silver oxide in addition to the above components. The content of silver oxide is not particularly limited, but is preferably 0.02 wt % or more, more preferably 0.1 wt % or more, and preferably 3.2 wt % or less, and even more preferably 3.0 wt % or less, calculated as AgO, per 100 parts by weight of the main component. The inclusion of silver oxide improves density, reduces porosity, and improves voltage resistance characteristics. However, if the silver oxide content is too high, the initial permeability and resistivity tend to decrease.

[0035] Furthermore, in addition to the above components, the magnetic layer 2 may contain additional components such as manganese oxides such as MnO, zirconium oxide, magnesium oxide, glass compounds, etc. The content of these additional components is not particularly limited as long as it does not impair the effects of this embodiment, and may be, for example, 1 part by weight or less.

[0036] Furthermore, the magnetic layer 2 may contain oxides of unavoidable impurity elements. Specific examples of unavoidable impurity elements include typical metal elements such as C, S, Cl, As, Se, Br, Te, and I, as well as Li, Na, Mg, Al, Ca, Ga, Ge, Sr, Cd, In, Sb, Ba, and Pb, and transition metal elements such as Sc, Ti, V, Cr, Y, Nb, Mo, Pd, Hf, and Ta. The oxides of the unavoidable impurity elements are preferably contained in the magnetic layer 2 in an amount of about 0.05 parts by weight or less.

[0037] Observing a cross section of a magnetic material 2 having the above-described composition reveals that the magnetic material layer 2 has a main phase 12 made of spinel ferrite and a grain boundary phase 16 containing silicon oxide and bismuth oxide, as shown in Fig. 2. Fig. 3 shows a Bi element mapping image of the magnetic material layer 2 obtained using STEM-EDS at a magnification of 100,000 times.

[0038] The main phase 12 is mainly composed of the main components described above, and the grain boundary phase 16 is a phase containing at least silicon oxide and bismuth oxide. As shown in Figure 3, when observing the distribution of Bi in the cross section of the magnetic layer 2, the concentration of Bi is higher at the position of the grain boundary phase 16 shown in Figure 2 than in the main phase 12. This, combined with the oxygen mapping image, confirms that the grain boundary phase 16 contains bismuth oxide.

[0039] Similarly, when the distribution of Si is observed in the cross section of the magnetic layer 2, it is confirmed that the concentration of Si is higher at the position of the grain boundary phase 16 shown in Fig. 2 than in the main phase 12, and when combined with the oxygen mapping image, it is confirmed that silicon oxide is contained in the grain boundary phase 16. Note that a composite oxide of bismuth oxide and silicon oxide may be formed in the grain boundary phase 16.

[0040] The grain boundary phase 16 may contain elements other than bismuth and silicon, but the total mole percentage of bismuth and silicon in the grain boundary phase 16 is 6.50 mole percent or more, where the total mole percentage of the elements contained in the grain boundary phase excluding oxygen is 100 mole percent, and no other elements may be contained. Alternatively, the grain boundary phase may contain elements other than bismuth and silicon in an amount of 96.0 mole percent or less, where the total mole percentage of the elements contained in the grain boundary phase excluding oxygen is 100 mole percent. Examples of elements that may be contained in the grain boundary phase excluding oxygen include the above-mentioned elements of the main components and subcomponents, additional components, and unavoidable impurities.

[0041] In the grain boundary phase 16, the molar ratio of bismuth to silicon is not particularly limited and is in the range of 1.00:0.05 to 1.00:0.59.

[0042] 2, the magnetic layer 2 may include voids. The ratio of the area of ​​voids to the area of ​​the field of view in cross-sectional observation of the magnetic layer 2, i.e., the porosity, is preferably small, and is preferably 12% or less, 9% or less, and 7.3% or less, in that order.

[0043] In this embodiment, in a STEM-EDS image of the magnetic layer 2 at a magnification of, for example, 20,000 times or more, where the main phase 12 is visible, the area ratio of the main phase 12 to the grain boundary phase 16, excluding voids and where the total area of ​​the main phase 12 and the grain boundary phase 16 is 100%, is preferably 92:8 to 99:1, and more preferably 93:7 to 98:2. This configuration makes it possible to obtain a multilayer chip coil 1 that can achieve excellent withstand voltage characteristics while maintaining high magnetic permeability.

[0044] The average particle size of the main phase 12 in the magnetic layer 2 is preferably 0.27 to 0.6 μm, and more preferably 0.27 to 0.5 μm. Any method can be used to measure the average particle size. For example, there is a method of measuring the cross section of the magnetic layer 2 using an electron microscope such as SEM or STEM, or a method of measuring using XRD.

[0045] Next, an example of a method for manufacturing the chip coil 1 according to this embodiment will be described. First, the starting materials (raw materials of the main components and raw materials of the subcomponents) are weighed out so as to have a predetermined composition ratio. It is preferable to use starting materials with an average particle size of 0.05 to 3.00 μm.

[0046] As raw materials for the main components, iron oxide (α-Fe2O3), copper oxide (CuO), nickel oxide (NiO), zinc oxide (ZnO), or composite oxides can be used. Examples of the composite oxides include zinc silicate (Zn2SiO4). Furthermore, various compounds that become the above-mentioned oxides or composite oxides upon firing can also be used. Examples of materials that become the above-mentioned oxides upon firing include elemental metals, carbonates, oxalates, nitrates, hydroxides, halides, and organometallic compounds.

[0047] As raw materials for the minor components, silicon oxide, bismuth oxide, cobalt oxide, and silver oxide can be used. There are no particular limitations on the oxides used as raw materials for the minor components, and composite oxides can be used. An example of the composite oxide is zinc silicate (Zn2SiO4). In addition, various compounds that become the above-mentioned oxides or composite oxides upon firing can be used. Examples of compounds that become the above-mentioned oxides upon firing include elemental metals, carbonates, oxalates, nitrates, hydroxides, halides, and organometallic compounds.

[0048] Co3O4, which is one form of cobalt oxide, is easy to store and handle, and its valence is stable even in air, making it a preferred raw material for cobalt compounds.

[0049] Next, the raw materials for the main components, iron oxide, copper oxide, nickel oxide, and zinc oxide, are mixed to obtain a raw material mixture. Furthermore, among the raw materials for the main components, zinc oxide may not be added at this stage, but may be added together with zinc silicate after the raw material mixture is calcined. Conversely, some of the raw materials for the minor components may be mixed with the raw materials for the main components at this stage. By appropriately controlling the types and ratios of the raw materials contained in the raw material mixture, the proportions of the main phase and the grain boundary phase can be controlled.

[0050] Specifically, the area ratio of the grain boundary phase tends to increase as the ZnO content in the raw material mixture decreases. Any mixing method can be used. For example, wet mixing using a ball mill or dry mixing using a dry mixer can be used.

[0051] Next, the raw material mixture is calcined to obtain a calcined material. Calcination is performed to thermally decompose the raw materials, homogenize the components, generate ferrite, eliminate ultrafine powder by sintering, and grow particles to an appropriate particle size, thereby converting the raw material mixture into a form suitable for subsequent processes. The calcination time and temperature are optional. Calcination is usually performed in the atmosphere (air), but it can also be performed in an atmosphere with a lower oxygen partial pressure than the atmosphere.

[0052] Next, the raw materials for the secondary components, such as silicon oxide, bismuth oxide, cobalt oxide, silver oxide, and zinc silicate, are mixed with the calcined material to produce a mixed calcined material. The more Bi there is in the calcined material, the greater the proportion (area percentage) of the grain boundary phase. Bismuth flows into the grain boundary phase during sintering, forming bismuth oxide in the grain boundary phase. It is thought that a certain area percentage of the grain boundary phase suppresses grain growth during sintering, improving both the voltage resistance characteristics and the magnetic permeability. Silicon is also thought to have a similar effect to bismuth.

[0053] Next, the mixed calcined material is pulverized to obtain a pulverized calcined material. The pulverization is carried out to break down agglomerates of the mixed calcined material and obtain a powder with appropriate sinterability. When the mixed calcined material forms large lumps, it is subjected to coarse pulverization and then wet pulverization using a ball mill, attritor, or the like. The wet pulverization is carried out until the average particle size of the pulverized calcined material is preferably about 0.1 to 3.00 μm.

[0054] Hereinafter, a method for manufacturing the multilayer chip coil 1 shown in FIG. 1A using the pulverized material after the wet pulverization will be described.

[0055] The multilayer chip coil 1 shown in FIG. 1A can be manufactured by a common manufacturing method. Specifically, the chip body 4 can be formed by alternately printing and laminating internal electrode paste containing Ag or the like using a ferrite paste obtained by kneading a pulverized calcined material with a binder and a solvent, followed by firing (printing method). Alternatively, the chip body 4 can be formed by preparing green sheets using the ferrite paste, printing the internal electrode paste on the surface of the green sheets, laminating them, and firing them (sheet method). In either case, after the chip body is formed, the terminal electrodes 5 can be formed by baking or plating.

[0056] The binder and solvent contents in the ferrite paste are arbitrary. For example, the binder content can be set to about 1 to 10 wt % and the solvent content can be set to about 10 to 50 wt % when the entire ferrite paste is 100 wt %. Furthermore, the ferrite paste can contain dispersants, plasticizers, dielectrics, insulators, etc., in the range of 10 wt % or less, as needed. Internal electrode pastes containing Ag or the like can also be prepared in the same manner. Furthermore, the firing conditions are not particularly limited, but when Ag or the like is contained in the internal electrode layers, the firing temperature is preferably 930°C or less, more preferably 900°C or less.

[0057] The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention.

[0058] For example, the configuration of the multilayer coil component is not limited to the configuration shown in Fig. 1A, and may be a configuration such as the multilayer chip coil 1a shown in Fig. 1B. This coil 1a has a chip body 4a in which magnetic layers 2 and internal electrode layers 3a are alternately stacked in the Z-axis direction. The configuration of the magnetic layers 2 is the same as that of the magnetic body 2 in the above-described embodiment.

[0059] Each internal electrode layer 3a has a square ring, C-shape, or U-shape, and is spirally connected by a through-hole electrode (not shown) for connecting internal electrodes or a stepped electrode that penetrates adjacent magnetic layers 2, forming a coil conductor 30a.

[0060] Terminal electrodes 5, 5 are formed on both ends of the chip body 4a in the Y-axis direction. Each terminal electrode 5 is connected to the end of an extraction electrode 6a located above and below in the Z-axis direction, and each terminal electrode 5, 5 is connected to both ends of a coil conductor 30a that constitutes a closed magnetic circuit coil.

[0061] In this embodiment, the stacking direction of the magnetic layers 2 and the internal electrode layers 3 coincides with the Z axis, and the end faces of the terminal electrodes 5, 5 are parallel to the X axis and the Z axis. The X axis, Y axis, and Z axis are perpendicular to each other. In the multilayer chip coil 1a shown in FIG. 1B, the winding axis of the coil conductor 30a substantially coincides with the Z axis.

[0062] In the multilayer chip coil 1 shown in Fig. 1A, the winding axis of the coil conductor 30 is in the Y-axis direction, which is the longitudinal direction of the chip body 4, so it is possible to increase the number of turns compared to the multilayer chip coil 1a shown in Fig. 1B, which has the advantage of making it easier to achieve high impedance up to high frequency bands. The other configurations and effects of the multilayer chip coil 1a shown in Fig. 1B are the same as those of the multilayer chip coil 1 shown in Fig. 1A.

[0063] Furthermore, the multilayer coil component of this embodiment may be any component that has a portion having the above-described magnetic layer 2, and includes a multilayer composite electronic component that combines elements such as a coil and a capacitor.

[0064] The multilayer coil component of this embodiment can be used in any application, including circuits in ICT devices (such as smartphones) that use NFC technology or contactless power supply, where a particularly high AC current flows and therefore wire-wound ferrite inductors have traditionally been used. [Example]

[0065] More detailed examples will be described below, but the present invention is not limited to these examples.

[0066] Examples 1 to 5 First, Fe2O3 powder, NiO powder, CuO powder, and ZnO powder were prepared as raw materials for the main components. SiO2 powder, Bi2O3 powder, Co3O4 powder, and Ag2O powder were prepared as raw materials for the secondary components. The average particle size of the SiO2 powder raw material was 0.025 μm. The prepared raw materials for the main components and secondary components were weighed to obtain the composition listed in Table 1, and then the raw materials for the main components were wet-mixed in a ball mill for 24 hours to obtain a raw material mixture.

[0067] The resulting raw material mixture was dried and then calcined in air at 720°C for 10 hours to obtain a calcined material. The calcined material was then wet-ground in a ball mill for 16 hours while adding the subcomponent raw materials SiO powder, Bi powder, Co powder, and Ag powder to obtain a ground material.

[0068] After drying the pulverized material, 100% by weight of the pulverized material was mixed with 10.0% by weight of polyvinyl alcohol as a binder and granulated to form granules. The granules were then press-molded to a target molding density of 3.2 Mg / m. 3 Toroidal (dimensions: outer diameter 13 mm x inner diameter 6 mm x height 3 mm) and disk-shaped (dimensions: outer diameter 12 mm x height 2 mm) compacts were obtained.

[0069] These compacts were then sintered in air at 880-980°C for 2 hours to obtain toroidal core and disk samples as sintered bodies. The following characteristic evaluations were performed on the obtained samples. An X-ray fluorescence analyzer was used to confirm that there was almost no change in composition between the weighed raw material powder and the sintered compact.

[0070] <Area ratio of main phase and grain boundary phase> The cut surface of the toroidal core (corresponding to the cross section of the magnetic layer 2) was observed using EPMA and STEM-EDS. The observation magnification was 20,000 times or more, and an appropriate observation magnification was set appropriately for each example and comparative example. It was confirmed that a main phase consisting of a spinel ferrite phase, a grain boundary phase containing silicon oxide and bismuth oxide, and voids were observed in the cross section. Furthermore, the area ratio of the main phase to the grain boundary phase in the field of view was calculated from the STEM-EDS observation results. The results are shown in Table 1. Also, a photograph of the cross section of the sample in Example 3, in which Bi was elementally mapped using STEM-EDS, is shown in Figure 3.

[0071] <Porosity / average particle diameter> The toroidal core sample was cut and 100 μm of the cut surface was measured. 2 The above regions were observed using a scanning electron microscope (SEM), and SEM photographs were taken. These SEM photographs were then processed using software, and EDS analysis was also used to extract the main phase, grain boundary phase, and voids, and their respective areas were calculated. The void area ratio to the calculated total area of ​​the main phase and grain boundary phase was then taken as the porosity. The circle-equivalent diameter (Heywood diameter) of each main phase was also calculated, and the number average was taken as the average particle diameter. The results are shown in Table 1.

[0072] <density> The density of the toroidal core samples was calculated from their dimensions and weights, and the results are shown in Table 1.

[0073] <Initial permeability μi> Ten turns of copper wire were wound around the toroidal core sample, and the initial permeability μi was measured using an impedance analyzer (4991A manufactured by Agilent Technologies). The measurement conditions were a measurement frequency of 1 MHz and a measurement temperature of 25°C. In this example, an initial permeability of 35 or more was considered good, and an initial permeability of 40 or more was considered particularly good. The results are shown in Table 1.

[0074] <Temperature change rate of magnetic permeability> Additionally, these samples were evaluated for the temperature change rate of magnetic permeability. Specifically, the magnetic permeability was measured at 125°C. The change rate (%) relative to the magnetic permeability (initial magnetic permeability μi) at a reference temperature of 25°C was then calculated. In this example, a temperature change rate of 27% or less was considered good. The results are shown in Table 1.

[0075] <Resistivity ρ> In-Ga electrodes were applied to both sides of the disk sample, and the DC resistance was measured to determine the resistivity ρ (unit: Ω m). The measurement was performed using an IR meter (4329A manufactured by Hewlett Packard). In this example, the resistivity ρ was 1.0×10 6 A resistance of Ω·m or more (1.0E+06Ω·m or more) was considered good. The results are shown in Table 1.

[0076] <Withstand voltage (breakdown voltage value)> Capacitor samples were fabricated using the same pulverized material as the toroidal core described above. Specifically, a green laminate for forming a capacitor circuit was produced by printing so that after firing, the conductor layer would be 0.7 μm thick, the ceramic layer (magnetic layer) would be 5 μm thick, and the number of conductor layers would be three. Ag particles were used as the conductor raw material. The green laminate was fired in air at 860-900°C for 2 hours to produce a sintered chip with a rectangular parallelepiped shape measuring 1.6 mm x 0.8 mm x 0.8 mm. In-Ga terminal electrode paste was applied to both end faces of the resulting sintered chip, dried, and then baked at 700°C for 1 hour in an atmosphere with a 1% oxygen partial pressure.

[0077] Then, electrolytic plating was performed to form Ni and Sn plating layers on the terminal electrodes, thereby forming the terminal electrodes and obtaining capacitor samples. The capacitor samples were evaluated for withstand voltage as follows.

[0078] For five or more capacitor samples, a DC voltage was applied to the samples at a rate of 10 V / sec. The voltage at which a leakage current of 10 mA was observed was measured and divided by the thickness between the conductors to determine the value. The average of these values ​​was used as the breakdown voltage value (withstand voltage). Withstand voltages of 16 V / μm or more were considered good, and those of 20 V / μm or more were considered particularly good. The results are shown in Table 1.

[0079] [Table 1]

[0080] Comparative Examples 1 and 2 Except for adjusting the raw materials of the subcomponents so that the content ratios of Bi2O3 powder and SiO2 were as shown in Table 1, toroidal core samples, disk samples, and capacitor samples were prepared in the same manner as in Example 1, and evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0081] Rating 1 From the results shown in Table 1, it was confirmed that in Examples 1 to 5, in which the area ratio of the main phase to the grain boundary phase in the magnetic layer satisfies the predetermined range, the magnetic permeability and withstand voltage characteristics are improved compared to Comparative Examples 1 and 2. It was also confirmed that the magnetic permeability and withstand voltage characteristics are improved by including 0.02 to 3.0 wt %, and preferably 0.10 to 2.0 wt %, of bismuth oxide calculated as Bi2O3 relative to 100 wt % of the main component.

[0082] Examples 6 to 10

[0083] Samples were prepared under the same conditions as in Example 1, except that the mixing ratio of the raw materials was adjusted so that the ratio of SiO2 in the subcomponents was the value shown in Table 2. The obtained samples were evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0084] [Table 2]

[0085] Rating 2 The results shown in Table 2 indicate that controlling the SiO2 ratio changes the average particle size, and when the average particle size of the main phase is within a predetermined range, the area ratio between the main phase and the grain boundary phase satisfies a predetermined range, improving the magnetic permeability and withstand voltage characteristics. It was also confirmed that when the average particle size is 0.27 to 0.6 μm, and more preferably 0.27 to 0.5 μm, the magnetic permeability and withstand voltage characteristics are improved.

[0086] Examples 11 to 15 Samples were prepared under the same conditions as in Example 3, except that the mixing ratio of the raw materials was adjusted so that the ratio of the main component raw materials was the value shown in Table 3. The obtained samples were evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0087] [Table 3]

[0088] Rating 3 From the results shown in Table 3, it was confirmed that if the amount of iron oxide as the main component is within a predetermined range, the area ratio between the main phase and the grain boundary phase will satisfy a predetermined range, thereby achieving a good balance between density, porosity, magnetic permeability, the temperature characteristics of magnetic permeability, and voltage resistance characteristics. It was also confirmed that the predetermined range of iron oxide as the main component is preferably 24.0 to 50.0 mol%, and more preferably 26.0 to 49.8 mol%, calculated as Fe2O3.

[0089] Examples 16 to 19 Samples were prepared under the same conditions as in Example 3, except that the mixing ratio of the raw materials was adjusted so that the ratio of the main component raw materials was the value shown in Table 4. The obtained samples were evaluated in the same manner as in Example 1. The results are shown in Table 4.

[0090] [Table 4]

[0091] Rating 4 From the results shown in Table 4, it was confirmed that if the amount of copper oxide as the main component is within a predetermined range, the area ratio between the main phase and the grain boundary phase will satisfy a predetermined range, thereby achieving a good balance between density, porosity, magnetic permeability, temperature characteristics of magnetic permeability, withstand voltage characteristics, and resistivity. It was also confirmed that the predetermined range of copper oxide as the main component, calculated as CuO, is preferably 2.2 to 12.0 mol %, more preferably 5.0 to 10.0 mol %.

[0092] Examples 20 to 23 Samples were prepared under the same conditions as in Example 3, except that the mixing ratio of the raw materials was adjusted so that the ratio of the main component raw materials was the value shown in the table. The obtained samples were evaluated in the same manner as in Example 1. The results are shown in Table 5.

[0093] [Table 5]

[0094] Rating 5 From the results shown in Table 5, it was confirmed that if the amount of zinc oxide as the main component is within a predetermined range, the area ratio between the main phase and the grain boundary phase will satisfy a predetermined range, thereby achieving a good balance between density, porosity, magnetic permeability, temperature characteristics of magnetic permeability, withstand voltage characteristics, and resistivity. It was also confirmed that the predetermined range of zinc oxide as the main component is 12.3 to 39.0 mol%, more preferably 13.0 to 37.9 mol%, calculated as ZnO.

[0095] Examples 24 to 27 Samples were prepared under the same conditions as in Example 3, except that the mixing ratio of the raw materials for the minor components was adjusted so that the ratios were as shown in the table. The obtained samples were evaluated in the same manner as in Example 1. The results are shown in Table 6.

[0096] [Table 6]

[0097] Rating 6 From the results shown in Table 6, it was confirmed that when the area ratio of the main phase to the grain boundary phase satisfies a predetermined range, and silicon oxide is contained as a secondary component, preferably in an amount of 0.02 to 3.0 wt %, more preferably 0.1 to 3.0 wt %, and particularly preferably 0.1 to 2.0 wt %, calculated as SiO2 relative to 100 wt % of the main component, a good balance of density, porosity, magnetic permeability, temperature characteristics of magnetic permeability, withstand voltage characteristics, and resistivity is achieved.

[0098] Examples 28 to 31 Samples were prepared under the same conditions as in Example 3, except that the mixing ratio of the raw materials for the minor components was adjusted so that the ratios were as shown in the table. The obtained samples were evaluated in the same manner as in Example 1. The results are shown in Table 7.

[0099] [Table 7]

[0100] Rating 7 From the results shown in Table 7, it was confirmed that when the area ratio of the main phase to the grain boundary phase satisfies a predetermined range, and bismuth oxide is contained as a minor component in an amount of preferably 0.02 to 3.0 wt %, more preferably 0.10 to 2.0 wt %, calculated as Bi2O3, a good balance of density, porosity, magnetic permeability, temperature characteristics of magnetic permeability, withstand voltage characteristics, and resistivity is achieved.

[0101] Examples 32 to 36 Samples were prepared under the same conditions as in Example 3, except that the mixing ratio of the raw materials for the minor components was adjusted so that the ratios were as shown in Table 8. The obtained samples were evaluated in the same manner as in Example 1. The results are shown in Table 8. [Table 8]

[0102] Rating 8 The results shown in Table 8 confirm that cobalt oxide does not need to be included as a secondary component as long as the area ratio of the main phase to the grain boundary phase satisfies the specified range. However, it was confirmed that the inclusion of cobalt oxide is preferable, and that a content of 0.1 to 4.0 wt. % (equivalent to Co3O4), and more preferably 0.1 to 3.0 wt. %, provides a good balance between density, porosity, magnetic permeability, temperature characteristics of magnetic permeability, withstand voltage characteristics, and resistivity.

[0103] Examples 37 to 41 Samples were prepared under the same conditions as in Example 3, except that the mixing ratio of the raw materials for the minor components was adjusted so that the ratios were as shown in Table 9. The obtained samples were evaluated in the same manner as in Example 1. The results are shown in Table 9. [Table 9]

[0104] Rating 9 The results shown in Table 9 confirm that silver oxide does not need to be included as a minor component as long as the area ratio of the main phase to the grain boundary phase satisfies the specified range. However, it is preferable that silver oxide is included, and it was confirmed that a content of preferably 0.02 to 3.2 wt%, more preferably 0.02 to 3.0 wt%, calculated as AgO, or 0.1 to 3.0 wt%, taking other tables into consideration, of silver oxide provides a good balance of density, porosity, magnetic permeability, temperature characteristics of magnetic permeability, withstand voltage characteristics, and resistivity. [Explanation of symbols]

[0105] 1,1a... Multilayer chip coil 2... Magnetic layer 3,3a… Internal electrode layer 4,4a... Chip body 5…Terminal electrode 6...Through-hole electrode for terminal connection 6a... Extraction electrode 12... Main phase (spinel ferrite phase) 16… Grain boundary phase 30, 30a... Coil conductor

Claims

1. A multilayer coil component having a magnetic layer, The magnetic layers have a main phase made of spinel ferrite and a grain boundary phase containing silicon oxide and bismuth oxide, and the area ratio of the main phase to the grain boundary phase is 92:8 to 99:

1.

2. the magnetic layer has a ferrite composition containing a main component and a subcomponent, The main component is iron oxide, Fe 2 O 3 24.0 to 50.0 mol % in terms of CuO of copper oxide, 2.2 to 12.0 mol % in terms of CuO of zinc oxide, 12.3 to 39.0 mol % in terms of ZnO of zinc oxide, and the remainder being nickel oxide, The auxiliary component is bismuth oxide in an amount of Bi with respect to 100% by weight of the main component. 2 O 3 2. The multilayer coil component according to claim 1, wherein the content is 0.02 to 3.0% by weight in terms of the total weight of the composite material.

3. As a secondary component, silicon oxide (SiO) is used relative to 100% by weight of the main component. 2 3. The laminated coil component according to claim 1 or 2, wherein the content is 0.02 to 3.0% by weight in terms of the total weight of the composite material.

4. Cobalt oxide is used as a secondary component relative to 100% by weight of the main component. 3 O 4 3. The multilayer coil component according to claim 1, wherein the content is 0.1 to 4.0% by weight in terms of the total weight of the composite material.

5. Silver oxide is used as a secondary component relative to 100% by weight of the main component. 2 3. The laminated coil component according to claim 1, wherein the content is 0.02 to 3.2% by weight in terms of O.

6. 3. The laminated coil component according to claim 1, wherein the average grain size of the main phase is 0.27 to 0.6 μm.

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