Laminated coil component

Abstract

The present invention relates to a laminated coil component having excellent magnetic permeability and voltage resistance. The laminated coil component has a magnetic layer having a main phase comprising spinel ferrite and a grain boundary phase containing a silicon oxide and a bismuth oxide, the area ratio of the main phase to the grain boundary phase being 92: 8 to 99: 1.

Description

Technical Field

[0001] The present invention relates to a laminated coil component. Background Art

[0002] In recent years, as ICT devices have become increasingly miniaturized, the ferrite chip bead products used have also become increasingly smaller. In the case of laminated ferrite chip bead products, the internal inter-electrode layer must be thinned to achieve miniaturization. However, if the inter-layer insulation is not achieved, short circuits can occur. Therefore, ferrite materials require designs that not only reduce the size of the gaps that create low withstand voltage areas, but also reduce the porosity and particle size.

[0003] Patent Document 1 discloses a ferrite material that uses NiCuZn-based ferrite containing tin oxide and potassium oxide, exhibiting excellent DC superposition performance and capable of controlling the particle size after sintering to 1.3 μm or less. However, the material used between the thinned layers results in a very large particle size.

[0004] Patent Document 2 discloses a ferrite material with increased density and magnetic permeability by controlling the mixing ratio of magnetic and non-magnetic materials to between 20% by weight:80% by weight and 80% by weight:20% by weight. However, increasing the proportion of non-magnetic material fragments the magnetic path, resulting in a material with low magnetic permeability.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2011-213578

[0008] Patent Document 2: Japanese Patent Application Laid-Open No. 2014-220469 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] An object of the present invention is to provide a laminated coil component having high magnetic permeability and excellent voltage resistance.

[0011] Technical means to solve problems

[0012] In order to achieve the above-mentioned purpose, an embodiment of the present invention involves a stacked coil component, wherein the stacked coil component has: a magnetic layer, the magnetic layer has: a main phase composed 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.

[0013] This laminated coil component not only increases magnetic permeability but also improves withstand voltage performance.

[0014] The magnetic layer preferably comprises a ferrite composition comprising a main component and a secondary component. The main component preferably comprises 24.0 to 50.0 mol%, more preferably 26.0 to 49.8 mol%, of iron oxide (as converted to Fe₂O₃); 2.2 to 12.0 mol%, more preferably 5.0 to 10.0 mol%, of copper oxide (as converted to CuO); 12.3 to 39.0 mol%, more preferably 13.0 to 37.9 mol%, of zinc oxide (as converted to ZnO); and the remainder being nickel oxide. Furthermore, the secondary component preferably comprises 0.02 to 3.0 wt%, more preferably 0.10 to 2.0 wt%, of bismuth oxide (as converted to Bi₂O₃) relative to 100 wt% of the main component.

[0015] As a secondary component, silicon oxide may be further included, preferably in an amount of 0.02 to 3.0 wt % in terms of SiO 2 relative to 100 wt % of the main component, more preferably 0.1 to 3.0 wt %, and particularly preferably 0.1 to 2.0 wt %.

[0016] Cobalt oxide may be further contained as a secondary component, and its content is preferably 0.1 to 4.0 wt % in terms of Co 3 O 4 relative to 100 wt % of the main component, more preferably 0.1 to 3.0 wt %.

[0017] As a secondary component, silver oxide may be further included, preferably in an amount of 0.02 to 3.2 wt % in terms of Ag 2 O relative to 100 wt % of the main component, more preferably 0.02 to 3.0 wt % or 0.1 to 3.0 wt %.

[0018] The average particle size of the main phase is preferably 0.27 to 0.6 μm, more preferably 0.27 to 0.5 μm. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1A This is a perspective view showing the interior of a laminated coil component according to one embodiment of the present invention.

[0020] Figure 1B This is a perspective view of the interior of a laminated coil component according to another embodiment of the present invention.

[0021] Figure 2 for Figure 1A Schematic diagram of a cross-sectional SEM image of a magnetic layer of a laminated coil component shown.

[0022] Figure 3This is a photograph of a cross section of a magnetic layer of a laminated coil component according to an embodiment of the present invention obtained by performing elemental mapping using STEM-EDS.

[0023] Explanation of symbols

[0024] 1,1a…Laminated chip coil

[0025] 2…Magnetic layer

[0026] 3,3a…Internal electrode layer

[0027] 4,4a…Chip body

[0028] 5…Terminal electrode

[0029] 6…Through-hole electrodes for terminal connection

[0030] 6a…lead-out electrode

[0031] 12…Main phase (spinel ferrite phase)

[0032] 16…Grain boundary phase

[0033] 30,30a…Coil conductor DETAILED DESCRIPTION

[0034] Hereinafter, embodiments will be described.

[0035] like Figure 1A As shown, a laminated chip coil 1 as a laminated coil component according to one embodiment of the present invention includes a chip body 4 in which magnetic layers (ceramic layers) 2 and internal electrode layers 3 are alternately laminated in the Y-axis direction.

[0036] Each internal electrode layer 3 has a rectangular ring shape, a C shape, or a U shape, and is spirally connected via internal electrode connection via electrodes (not shown) or step electrodes penetrating adjacent magnetic layers 2 to form a coil conductor 30 .

[0037] Terminal electrodes 5, 5 are formed at both ends of the chip body 4 in the Y-axis direction. The ends of terminal connection through-hole electrodes 6 that penetrate the stacked magnetic layers 2 are connected to each terminal electrode 5, and each terminal electrode 5, 5 is connected to the ends of a coil conductor 30 that forms a closed magnetic circuit coil (winding form).

[0038] In this embodiment, the stacking direction of the magnetic layer 2 and the internal electrode layer 3 is aligned with the Y 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. Figure 1A In the case of the multilayer chip coil 1 shown, the winding axis of the coil conductor 30 substantially coincides with the Y axis.

[0039] There is no special restriction on the shape and size of the chip body 4, which can be appropriately set according to the purpose. Usually, the shape is set to be nearly rectangular, for example, the X-axis size is 0.125~0.8mm, the Y-axis size is 0.25~1.6mm, and the Z-axis size is 0.1~1.0mm.

[0040] Furthermore, the inter-electrode thickness and base thickness of the magnetic layer 2 are not particularly limited; the inter-electrode thickness (the distance between the internal electrode layers 3, 3) can be set to 2.5 to 50 μm, and the base thickness (the Y-axis length of the terminal connection through-hole electrode 6) can be set to 5 to 300 μm. In this embodiment, even when the inter-electrode thickness of the magnetic layer 2 is reduced to 2.0 μm or less, a laminated coil component with high magnetic permeability and excellent withstand voltage performance can be obtained.

[0041] In this embodiment, the terminal electrodes 5 are not particularly limited and can be formed by applying a conductive paste containing Ag or Pd as a main component to the outer surface of the main body 4, baking it, and then performing electroplating. Cu, Ni, Sn, etc. can be used for the electroplating.

[0042] The coil conductor 30 contains Ag (including an alloy of Ag), and is composed of, for example, Ag alone, an Ag-Pd alloy, etc. As auxiliary components of the coil conductor, Zr, Fe, Mn, Ti, and oxides thereof may be contained.

[0043] The magnetic layer 2 is composed of a ferrite composition containing a main component and a subcomponent. The ferrite composition will be described in detail below.

[0044] The main components include: iron oxide, copper oxide, zinc oxide and nickel oxide.

[0045] The content of iron oxide, 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, per 100 mol% of the main component. If the content of iron oxide is too low, the initial magnetic permeability tends to decrease. If the content of iron oxide is too high, the temperature performance of the magnetic permeability tends to deteriorate.

[0046] The content of copper oxide, calculated as CuO, is preferably 2.2 mol% or more, more preferably 5.0 mol% or more, and preferably 12.0 mol% or less, more preferably 10.0 mol% or less, per 100 mol% of the main component. If the copper oxide content is too low, the density and specific resistivity often decrease, and the initial magnetic permeability also decreases. This is believed to be due to poor sintering properties. If the copper oxide content is too high, the initial magnetic permeability or specific resistivity often decreases. This is believed to be due to copper oxide segregation.

[0047] The zinc oxide content, calculated as ZnO, is preferably 12.3 mol% or more, more preferably 13.0 mol% or more, and preferably 39.0 mol% or less, more preferably 37.9 mol% or less, based on 100 mol% of the main component. If the zinc oxide content is too low, the specific resistivity and withstand voltage (breakdown voltage) tend to decrease. If the zinc oxide content is too high, the resistivity and initial magnetic permeability tend to decrease.

[0048] The balance of the main component is made 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.

[0049] The magnetic layer 2 contains at least bismuth oxide and silicon oxide as accessory components in addition to the above-mentioned main component.

[0050] The bismuth oxide content, 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, more preferably 2.0 parts by weight or less, per 100 parts by weight of the main component. If the bismuth oxide content is too low, initial magnetic permeability or resistivity may decrease. This is believed to be due to poor sintering properties. If the bismuth oxide content is too high, resistivity may decrease. This is believed to be due to abnormal bismuth grain growth.

[0051] The content of silicon oxide, calculated as SiO2, is preferably 0.02% by weight or more, more preferably 0.10% by weight or more, relative to 100 parts by weight of the main component. It can preferably be 3.0% by weight or less, more preferably 2.30% by weight or less, or 2.00% by weight or less. The inclusion of silicon oxide not only reduces the average particle size but also increases resistivity and withstand voltage. However, excessive silicon oxide content often leads to reduced density and resistivity. This is believed to be due to poor sintering properties.

[0052] In addition to the above components, the magnetic layer 2 may also contain cobalt oxide. The content of cobalt oxide is not particularly limited, but is preferably 0.1% by weight or greater, more preferably 4.0% by weight or less, and even more preferably 3.0% by weight or less, calculated as Co₃O₄, relative to 100 parts by weight of the main component. The inclusion of cobalt oxide increases density, resistivity, and withstand voltage performance. However, excessive cobalt oxide content often results in decreased density, lower initial magnetic permeability, and decreased resistivity.

[0053] In addition to the above components, the magnetic layer 2 may also contain silver oxide. The silver oxide content is not particularly limited, but is preferably 0.02% by weight or greater, more preferably 0.1% by weight or greater, and preferably 3.2% by weight or less, more preferably 3.0% by weight or less, calculated as Ag2O, relative to 100 parts by weight of the main component. The inclusion of silver oxide increases density, reduces porosity, and improves withstand voltage performance. However, excessive silver oxide content often results in decreased initial magnetic permeability and resistivity.

[0054] In addition to the above components, the magnetic layer 2 may also contain additional components such as manganese oxides such as Mn3O4, zirconium oxides, magnesium oxides, and glass compounds. The content of these additional components is not particularly limited within the range that does not impair the effects of the embodiment of the present invention, and is, for example, 1 part by weight or less.

[0055] Furthermore, the magnetic layer 2 may contain oxides of inevitable impurity elements. Specifically, examples of inevitable impurity elements include typical metal elements such as C, S, Cl, As, Se, Br, Te, I, or 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 inevitable impurity elements are preferably present in the magnetic layer 2 in an amount of 0.05 parts by weight or less.

[0056] Observing the cross section of the magnetic layer 2 having the above composition, Figure 2 As shown, the magnetic layer 2 has a main phase 12 composed of spinel ferrite and a grain boundary phase 16 containing silicon oxide and bismuth oxide. In addition, the Bi element mapping image of the magnetic layer 2 obtained by STEM-EDS at a magnification of 100,000 times is shown in FIG. Figure 3 .

[0057] The main phase 12 is mainly composed of the main components of the above composition, and the grain boundary phase 16 is a phase containing at least silicon oxide and bismuth oxide. Figure 3 As shown, the distribution of Bi at the cross section of the magnetic layer 2 can be confirmed: Figure 2 The position of the grain boundary phase 16 shown has a higher concentration of Bi than the main phase 12 , which, combined with the mapping image of oxygen, indicates that the grain boundary phase 16 contains bismuth oxide.

[0058] In addition, the distribution of Si in the cross section of the magnetic layer 2 can be observed to confirm that: Figure 2The grain boundary phase 16 shown has a higher Si concentration than the main phase 12. This, combined with the oxygen mapping pattern, indicates that the grain boundary phase 16 contains silicon oxide. Note that a composite oxide of bismuth oxide and silicon oxide may also form in the grain boundary phase 16.

[0059] Furthermore, the grain boundary phase 16 may contain elements other than bismuth and silicon. In the grain boundary phase 16, the combined mol% of bismuth and silicon is 6.50 mol% or greater, based on 100 mol% of the total molar amount of elements contained in the grain boundary phase excluding oxygen. The grain boundary phase 16 may contain no other elements. Alternatively, the grain boundary phase may contain no more than 96.0 mol% of elements other than bismuth and silicon, based on 100 mol% of the total molar amount of elements contained in the grain boundary phase excluding oxygen. Examples of elements other than oxygen that may be contained in the grain boundary phase include the above-mentioned main and secondary components, additional components, and unavoidable impurities.

[0060] The molar ratio of bismuth to silicon in the grain boundary phase 16 is not particularly limited, but is in the range of 1.00:0.05 to 1.00:0.59.

[0061] Although Figure 2 Although not shown in the figure, the magnetic layer 2 may actually contain voids. The ratio of the void area to the viewing area in cross-sectional observation of the magnetic layer 2, i.e., the porosity, is preferably small, for example, preferably 12% or less, 9% or less, and 7.3% or less, respectively.

[0062] In this embodiment, the magnetic layer 2 preferably has an area ratio of 92:8 to 99:1, more preferably 93:7 to 98:2, in a STEM-EDS image of the main phase 12 visible at a magnification of, for example, 20,000x or greater, with the total area of ​​the main phase 12 and the grain boundary phase 16 excluding voids being 100%. This configuration allows for a laminated chip coil 1 that maintains high magnetic permeability while achieving excellent withstand voltage performance.

[0063] The average particle size of the main phase 12 in the magnetic layer 2 is preferably 0.27 to 0.6 μm, more preferably 0.27 to 0.5 μm. The average particle size can be measured by any of a variety of methods. Examples include measuring the cross-section of the magnetic layer 2 using an electron microscope such as a SEM or STEM, or measuring using XRD.

[0064] Next, an example of a method for manufacturing the chip coil 1 according to an embodiment of the present invention is described. First, starting materials (main component materials and auxiliary component materials) are weighed according to a predetermined composition ratio. It is preferable to use starting materials with an average particle size of 0.05 to 3.00 μm.

[0065] As the raw material of the main component, iron oxide (α-Fe2O3), copper oxide (CuO), nickel oxide (NiO), zinc oxide (ZnO), or a composite oxide can be used. Examples of the composite oxide include zinc silicate (Zn2SiO4). In addition, various compounds of the above oxides or composite oxides formed by calcination can also be used. Examples of the above oxide compounds formed by calcination include metal elements, carbonates, oxalates, nitrates, hydroxides, halides, and organometallic compounds.

[0066] As the raw materials of the auxiliary components, silicon oxide, bismuth oxide, cobalt oxide and silver oxide can be used. As the oxide forming the raw materials of the auxiliary components, composite oxides etc. can be used but are not particularly limited. As the above-mentioned composite oxides, for example, zinc silicate (Zn2SiO4) can be given. In addition, various compounds etc. formed by firing the above-mentioned oxides and / or composite oxides can also be used. As the compounds formed by firing the above-mentioned oxides, for example, metal elements, carbonates, oxalates, nitrates, hydroxides, halides, organometallic compounds etc. can be given.

[0067] It should be noted that Co 3 O 4 , which is one form of cobalt oxide, is preferred as a raw material for the cobalt compound because it is easy to store and handle and has a stable valence even in the air.

[0068] Next, the iron oxide, copper oxide, nickel oxide, and zinc oxide serving as the raw materials for the main component are mixed to form a raw material mixture. Alternatively, zinc oxide may be added to the raw materials for the main component, rather than at this stage, after the raw material mixture is calcined, along with zinc silicate. Alternatively, a portion of the secondary raw materials may be mixed with the raw materials for the main component at this stage. By appropriately controlling the types and ratios of the raw materials contained in the raw material mixture, the ratio of the main phase to the grain boundary phase can be controlled.

[0069] Specifically, the lower the ZnO content in the raw material mixture, the higher the area ratio of the grain boundary phase tends to be. The mixing method is optional. For example, wet mixing using a ball mill and dry mixing using a dry mixer can be mentioned.

[0070] Next, the raw material mixture is calcined to produce a calcined material. Calcination is performed to initiate thermal cracking of the raw materials, homogenize the components, form ferrite, eliminate ultrafine powders through sintering, grow the grains to a suitable particle size, and transform the raw material mixture into a form suitable for subsequent processing. The calcination time and temperature are optional. Calcination is typically performed in ambient air, but can also be performed at an oxygen partial pressure lower than atmospheric pressure.

[0071] Next, silicon oxide, bismuth oxide, cobalt oxide, silver oxide, and zinc silicate, which will serve as auxiliary raw materials, are mixed with the calcined material to produce a mixed calcined material. The higher the Bi content in the calcined material, the more likely it is that the proportion (area ratio) of the grain boundary phase increases. It is believed that this is because bismuth flows into the grain boundary phase during sintering and forms bismuth oxide in the grain boundary phase. The grain boundary phase with a specified area ratio can control grain growth during sintering, thereby improving the withstand voltage performance and increasing the magnetic permeability. It should be noted that silicon is believed to have the same effect as bismuth.

[0072] Next, the mixed calcined material is pulverized to produce a pulverized calcined material. This pulverization is performed to break up any agglomerates in the mixed calcined material and form a powder with suitable sinterability. If the mixed calcined material forms large agglomerates, it is coarsely pulverized and then wet-pulverized using a ball mill, grinder, or the like. Wet pulverization is performed until the average particle size of the pulverized calcined material reaches preferably 0.1 to 3.00 μm.

[0073] The following describes the process of using the pulverized material after wet pulverization. Figure 1A The manufacturing method of the laminated chip coil 1 is shown.

[0074] Figure 1A The stacked chip coil 1 shown can be manufactured by a conventional manufacturing method. That is, by using a ferrite paste obtained by mixing a pulverized calcined material with a binder and a solvent, and alternately printing and stacking it with an internal electrode paste containing Ag, etc., and then firing it, the chip body 4 can be formed (printing method). Alternatively, a green sheet can be prepared using ferrite paste, and the internal electrode paste can be printed on the surface of the green sheet, and they can be stacked and fired to form the chip body 4 (sheet method). In any case, the terminal electrode 5 can be formed by baking or plating after the chip body is formed.

[0075] The content of binder and solvent in ferrite paste is optional. For example, if the ferrite paste as a whole is 100 weight percent, the binder content can be set to about 1 to 10 weight percent, and the solvent content can be set to about 10 to 50 weight percent. In addition, the ferrite paste can contain a dispersant, plasticizer, dielectric, insulator, etc. in a range of 10 weight percent or less as needed. Internal electrode paste containing Ag and the like can also be prepared in the same way. In addition, the firing conditions are not particularly limited, but when Ag and the like are contained in the internal electrode layer, the firing temperature is preferably below 930°C, more preferably below 900°C.

[0076] It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention.

[0077] For example, the structure of the laminated coil component is not limited to Figure 1A The composition shown can be, for example, Figure 1B The coil 1a has a structure similar to that of the laminated chip coil 1a shown in FIG. This coil 1a includes a chip body 4a in which magnetic layers 2 and internal electrode layers 3a are alternately laminated in the Z-axis direction. The structure of the magnetic layers 2 is the same as that of the magnetic layers 2 in the above embodiment.

[0078] Each internal electrode layer 3a has a rectangular ring shape, a C shape, or a U shape, and is spirally connected via internal electrode connection via electrodes (not shown) or stepped electrodes penetrating adjacent magnetic layers 2 to form a coil conductor 30a.

[0079] Terminal electrodes 5, 5 are formed at both ends of the chip body 4a in the Y-axis direction. The ends of the lead-out electrodes 6a located above and below in the Z-axis direction are connected to the terminal electrodes 5, and the terminal electrodes 5, 5 are connected to both ends of the coil conductor 30a that constitutes the closed magnetic circuit coil.

[0080] In this embodiment, the stacking direction of the magnetic layer 2 and the internal electrode layer 3 is aligned 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. Figure 1B In the case of the multilayer chip coil 1 a shown, the winding axis of the coil conductor 30 a substantially coincides with the Z axis.

[0081] exist Figure 1A In the laminated chip coil 1 shown, the winding axis of the coil conductor 30 is located in the Y-axis direction, which is the longitudinal direction of the chip body 4. Figure 1B Compared with the laminated chip coil 1a shown in FIG. 1 , the number of turns can be increased, and the advantage is that high impedance can be easily achieved up to the high frequency range. Figure 1B The other structures and effects of the laminated chip coil 1a shown are the same as those of Figure 1A The laminated chip coils 1 shown are identical.

[0082] The laminated coil component of the present embodiment may be any component that partially includes "a portion having the magnetic layer 2 ," and also includes a laminated composite electronic component that combines elements such as a coil and a capacitor.

[0083] The laminated coil component of this embodiment can be used in a variety of applications. For example, it can be applied to circuits in ICT devices (such as smartphones) that utilize NFC technology or contactless charging, and can also be applied to circuits that have traditionally used winding ferrite inductors due to the flow of particularly high AC currents.

[0084] Example

[0085] More specific examples will be described below, but the present invention is not limited to these examples.

[0086] Examples 1 to 5

[0087] First, Fe2O3 powder, NiO powder, CuO powder, and ZnO powder were prepared as raw materials for the main component. Separately, SiO2 powder, Bi2O3 powder, CO3O4 powder, and Ag2O powder were prepared as raw materials for the auxiliary components. The average particle size of the SiO2 powder was 0.025 μm. The prepared raw materials for the main and auxiliary components were weighed according to the composition listed in Table 1. The raw materials for the main component were then wet-mixed in a ball mill for 24 hours to obtain a raw material mixture.

[0088] The resulting raw material mixture was dried and then calcined in air at 720°C for 10 hours to obtain a calcined material. Subsequently, the calcined material was added with auxiliary raw materials SiO2 powder, Bi2O3 powder, CO3O4 powder, and Ag2O powder, and wet-pulverized using a ball mill for 16 hours to obtain a pulverized material.

[0089] After the crushed material was dried, 10.0% by weight of polyvinyl alcohol as a binder was added to 100% by weight of the crushed material to form granules. The granules were press-molded to obtain a target molding density of 3.2 Mg / m 3 Ring-shaped (dimensions = outer diameter 13 mm×inner diameter 6 mm×height 3 mm) and disc-shaped (dimensions = outer diameter 12 mm×height 2 mm) molded bodies.

[0090] Each of these molded bodies was sintered in air at 880-980°C for 2 hours to obtain toroidal core samples and disc-shaped samples. The following performance evaluations were performed on these samples. Fluorescent X-ray analysis confirmed that there was little difference in composition between the weighed raw material powders and the sintered molded bodies.

[0091] <Area Ratio of Main Phase to Grain Boundary Phase>

[0092] The cut surface of the annular core (corresponding to the cross section of the magnetic layer 2) was observed by EPMA and STEM-EDS. The observation magnification was set to 20,000 times or more, and the appropriate observation magnification was appropriately set according to each embodiment and comparative example. It was also confirmed that a main phase composed of a spinel ferrite phase, a grain boundary phase containing silicon oxide and bismuth oxide, and voids were observed in the cross section. Moreover, the area ratio of the main phase to the grain boundary phase in the field of view was calculated based on the observation results of STEM-EDS. The results are shown in Table 1. In addition, a photograph of the elemental mapping of Bi on the cross section of the sample of Example 3 by STEM-EDS is shown in Table 1. Figure 3 .

[0093] <Porosity and Average Particle Size>

[0094] The ring core sample was cut and its cut surface was observed with a scanning electron microscope (SEM) at a depth of 100 μm. 2 The area above 100 mm was selected and an SEM photograph was taken. The SEM photograph was processed using software and analyzed using EDS to extract the main phase, grain boundary phase, and voids, and the areas of each were calculated. The ratio of the calculated void area to the total area of ​​the main phase and grain boundary phase was then defined as the void ratio. In addition, the equivalent circular diameter (Heywood diameter) of each main phase was calculated, and the number average of these equivalent circular diameters was defined as the average particle size. The results are shown in Table 1.

[0095] <density>

[0096] The density of the ring core samples was calculated based on the dimensions and weight. The results are shown in Table 1.

[0097] <Initial magnetic permeability μi>

[0098] Copper wire was wrapped 10 turns around the toroidal core sample, and the initial magnetic permeability μi was measured using an impedance analyzer (Agilent 4991A). The measurement conditions were set at a frequency of 1 MHz and a temperature of 25°C. In this example, an initial magnetic permeability of 35 or greater was considered good, and 40 or greater was considered particularly good. The results are shown in Table 1.

[0099] <Temperature Change Rate of Magnetic Permeability>

[0100] In addition, the temperature change rate of the magnetic permeability of these samples was evaluated. Specifically, the magnetic permeability at 125°C was measured, and the rate of change (%) relative to the magnetic permeability (initial magnetic permeability μi) at a reference temperature of 25°C was calculated. In this example, a temperature change rate of 27% or less was defined as good. The results are shown in Table 1.

[0101] <Resistivity ρ>

[0102] In-Ga electrodes were coated on both sides of the disk sample, and the DC resistance was measured to obtain the resistivity ρ (unit: Ω·m). The measurement was performed using an IR tester (4329A manufactured by Hewlett-Packard). In this example, the resistivity ρ was set at 1.0×10 6 The results are shown in Table 1.

[0103] <Withstand Voltage (Breakdown Voltage)>

[0104] The capacitor sample was prepared using the same crushed material as the above-mentioned toroidal core. Specifically, a green laminate for forming a capacitor circuit was prepared by a printing method so that the thickness of the conductor layer after firing was 0.7 μm, the thickness of the ceramic layer (magnetic layer) was 5 μm, and the number of conductor layers was 3. Ag particles were used as the conductor raw material. The green laminate was fired in air at 860-900°C for 2 hours to form a 1.6mm×0.8mm×0.8mm rectangular shaped fired body chip. In-Ga terminal electrode paste was applied to both end faces of the obtained fired body chip and dried, and then baked at 700°C for 1 hour in an environment with an oxygen partial pressure of 1%.

[0105] Electrolytic plating was then performed to form a nickel (Ni) plating layer and a tin (Sn) plating layer on the terminal electrodes, forming the terminal electrodes and obtaining capacitor samples. The withstand voltage of the capacitor samples was evaluated as shown below.

[0106] For 5 or more capacitor samples, a DC voltage was applied to the sample at a boost rate of 10V / second, and the voltage at which a leakage current of 10mA was observed was measured and divided by the thickness between the conductors to obtain the value. The average value of these was set as the breakdown voltage value (withstand voltage). The case where the withstand voltage was 16V / μm or more was defined as good, and the case where it was 20V / μm or more was defined as particularly good. The results are shown in Table 1.

[0107] [Table 1]

[0108]

[0109] Comparative Examples 1 and 2

[0110] Except for adjusting the raw materials of the auxiliary components so that the content ratio of Bi2O3 powder to SiO2 is as shown in Table 1, the same procedures as in Example 1 were followed to prepare toroidal core samples, disc-shaped samples, and capacitor samples, and the same evaluations as in Example 1 were performed. The results are shown in Table 1.

[0111] Evaluation 1

[0112] The results shown in Table 1 demonstrate that Examples 1 to 5, in which the area ratio of the main phase to the grain boundary phase in the magnetic layer satisfies the specified range, exhibit improved magnetic permeability and withstand voltage performance compared to Comparative Examples 1 and 2. Furthermore, it was demonstrated that a bismuth oxide content of 0.02 to 3.0% by weight, preferably 0.10 to 2.0% by weight, calculated as Bi₂O₃, relative to 100% by weight of the main component, improves magnetic permeability and withstand voltage performance.

[0113] Examples 6 to 10

[0114] 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 auxiliary component became 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.

[0115] [Table 2]

[0116]

[0117] Evaluation 2

[0118] The results shown in Table 2 show that by controlling the SiO2 ratio to change the average particle size, and keeping the average particle size of the main phase within a set range, the area ratio of the main phase to the grain boundary phase satisfies the set range, resulting in improved magnetic permeability and withstand voltage performance. Furthermore, it was confirmed that when the average particle size is 0.27 to 0.6 μm, and more preferably 0.27 to 0.5 μm, both magnetic permeability and withstand voltage performance improve.

[0119] Example 11 to Example 15

[0120] 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 raw materials of the main component became the value described in Table 3. The obtained samples were evaluated in the same manner as in Example 1. The results are shown in Table 3.

[0121] [Table 3]

[0122]

[0123] Rating 3

[0124] The results shown in Table 3 demonstrate that, when the amount of iron oxide as the main component is within a specified range, by ensuring that the area ratio of the main phase to the grain boundary phase satisfies the specified range, a good balance can be achieved in terms of density, porosity, magnetic permeability, and temperature performance of magnetic permeability, as well as withstand voltage performance. Furthermore, it was demonstrated that the range of the iron oxide as the main component, calculated as Fe2O3, is preferably 24.0 to 50.0 mol%, and more preferably 26.0 to 49.8 mol%.

[0125] Example 16 to Example 19

[0126] 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 raw materials of the main component became the values ​​shown in Table 4. The obtained samples were evaluated in the same manner as in Example 1. The results are shown in Table 4.

[0127] [Table 4]

[0128]

[0129] Rating 4

[0130] The results shown in Table 4 demonstrate that, when the amount of copper oxide as the main component is within a specified range, by ensuring that the area ratio of the main phase to the grain boundary phase satisfies the specified range, a good balance can be achieved in terms of density, porosity, magnetic permeability, temperature performance of magnetic permeability, withstand voltage performance, and resistivity. Furthermore, it was demonstrated that the specified range for the amount of copper oxide as the main component, calculated as CuO, is preferably 2.2 to 12.0 mol%, and more preferably 5.0 to 10.0 mol%.

[0131] Examples 20 to 23

[0132] 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 raw materials of the main component became the values ​​shown in Table 5. The obtained samples were evaluated in the same manner as in Example 1. The results are shown in Table 5.

[0133] [Table 5]

[0134]

[0135] Rating 5

[0136] The results shown in Table 5 demonstrate that, when the amount of zinc oxide as the main component is within a specified range, by ensuring that the area ratio of the main phase to the grain boundary phase satisfies the specified range, a good balance can be achieved among density, porosity, magnetic permeability, temperature performance of magnetic permeability, withstand voltage performance, and resistivity. Furthermore, it was demonstrated that the specified range for the amount of zinc oxide as the main component, calculated as ZnO, is preferably 12.3 to 39.0 mol%, and more preferably 13.0 to 37.9 mol%.

[0137] Examples 24 to 27

[0138] 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 raw materials of the auxiliary components became the values ​​shown in Table 6. The obtained samples were evaluated in the same manner as in Example 1. The results are shown in Table 6.

[0139] [Table 6]

[0140]

[0141] Rating 6

[0142] The results shown in Table 6 can confirm that by making the area ratio of the main phase to the grain boundary phase meet the set range, when the content of silicon oxide as a secondary component is preferably 0.02 to 3.0 weight% in terms of SiO2 relative to 100 weight% of the main component, more preferably 0.1 to 3.0 weight%, and particularly preferably 0.1 to 2.0 weight%, it will be possible to achieve a good balance among density, porosity, magnetic permeability, temperature performance of magnetic permeability, voltage resistance and resistivity.

[0143] Examples 28 to 31

[0144] 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 raw materials of the auxiliary components became the values ​​shown in Table 7. The obtained samples were evaluated in the same manner as in Example 1. The results are shown in Table 7.

[0145] [Table 7]

[0146]

[0147] Rating 7

[0148] The results shown in Table 7 can confirm that by making the area ratio of the main phase to the grain boundary phase meet the set range, when the content of bismuth oxide as a secondary component is preferably 0.02 to 3.0 weight% and more preferably 0.10 to 2.0 weight% in terms of Bi2O3, it will be possible to achieve a good balance among density, porosity, magnetic permeability, temperature performance of magnetic permeability, voltage resistance and resistivity.

[0149] Examples 32 to 36

[0150] 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 raw materials of the auxiliary components became the values ​​shown in Table 8. The obtained samples were evaluated in the same manner as in Example 1. The results are shown in Table 8.

[0151] [Table 8]

[0152]

[0153] Rating 8

[0154] The results shown in Table 8 demonstrate that, by ensuring that the area ratio of the main phase to the grain boundary phase falls within a predetermined range, it is possible to eliminate the need for cobalt oxide as a secondary component. However, it was demonstrated that the inclusion of cobalt oxide, preferably in a content of 0.1 to 4.0% by weight, and more preferably 0.1 to 3.0% by weight, calculated as Co₃O₄, achieves a good balance among density, porosity, magnetic permeability, temperature performance of magnetic permeability, withstand voltage performance, and resistivity.

[0155] Examples 37 to 41

[0156] 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 raw materials of the auxiliary components became the values ​​shown in Table 9. The obtained samples were evaluated in the same manner as in Example 1. The results are shown in Table 9.

[0157] [Table 9]

[0158]

[0159] Rating 9

[0160] The results shown in Table 9 demonstrate that, by ensuring that the area ratio of the main phase to the grain boundary phase falls within the specified range, it is not necessary to include silver oxide as a secondary component. However, it was demonstrated that the inclusion of silver oxide is preferred, with the content preferably being 0.02 to 3.2% by weight, more preferably 0.02 to 3.0% by weight, or, as shown in other tables, 0.1 to 3.0% by weight, calculated as Ag2O. This allows for a good balance of density, porosity, magnetic permeability, temperature performance of magnetic permeability, withstand voltage performance, and resistivity.

Claims

1. A laminated coil component, wherein: The laminated coil component comprises: a magnetic layer, The magnetic layer includes a main phase composed of spinel ferrite and a grain boundary phase containing silicon oxide and bismuth oxide, and an area ratio of the main phase to the grain boundary phase is 92:8 to 99:

1.

2. The laminated coil component according to claim 1, wherein The magnetic layer comprises a ferrite composition including a main component and a subcomponent, The main components are: iron oxide converted to Fe2O3 in an amount of 24.0 to 50.0 mol%, copper oxide converted to CuO in an amount of 2.2 to 12.0 mol%, zinc oxide converted to ZnO in an amount of 12.3 to 39.0 mol%, and the remainder is nickel oxide. The auxiliary component contains 0.02 to 3.0 wt% of bismuth oxide in terms of Bi2O3 relative to 100 wt% of the main component.

3. The laminated coil component according to claim 1 or 2, wherein: The content of silicon oxide as a secondary component is 0.02 to 3.0 wt % in terms of SiO 2 relative to 100 wt % of the main component.

4. The laminated coil component according to claim 1 or 2, wherein: The content of the cobalt oxide as a secondary component is 0.1 to 4.0 wt % in terms of Co 3 O 4 relative to 100 wt % of the main component.

5. The laminated coil component according to claim 1 or 2, wherein: The content of silver oxide as a secondary component is 0.02 to 3.2 wt % in terms of Ag 2 O relative to 100 wt % of the main component.

6. The laminated coil component according to claim 1 or 2, wherein: The average particle size of the main phase is 0.27 to 0.6 μm.

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