Patent Application
20200082964
The present invention relates to a composite magnetic body, a substrate including the composite magnetic body, and a high-frequency electronic component including the same.
In accordance with the increasing demand for downsizing, thinning, or cost reduction of wireless communication devices, high-frequency electronic components mounted thereon are also increasingly demanded to be downsized, thinned, or reduced in cost.
In recent years, a frequency band used for high-frequency electronic components mounted on a wireless communication device, such as a mobile phone and a wireless LAN communication device, reaches a gigahertz hand, for example, 2.4 GHz band for a wireless LAN. Examples of the high-frequency electronic components used in a gigahertz band include inductors including coils, antennas for wireless communication devices including inductors, and filters for high-frequency noise including inductors and capacitors. These high-frequency electronic components are also increasingly demanded to be downsized, thinned, or reduced in cost.
In particular, a plurality of high-frequency electronic components may be housed in a small space inside the wireless communication device, and a high-performance high-frequency electronic component having characteristics, such as high inductance, low insertion loss, high capacitance, and high electromagnetic shielding performance, is demanded.
For example, however, when a high-frequency electronic component including an inductor is miniaturized and reduced in height, the coil cannot help having a small diameter, and it is thereby difficult to improve the performance of the high-frequency electronic component due to reduction in Q value and inductance value. In these high-frequency electronic components, it is thereby necessary to use a magnetic material having a high permeability and a low magnetic loss as a magnetic core material of the coil.
As a composite magnetic material having a high permeability and a low magnetic loss in a high-frequency region of gigahertz band, Patent Document 1 discloses a composite magnetic material in which a magnetic oxide whose main phase is hexagonal ferrite is dispersed in a resin. The composite magnetic material of Patent Document 1 contains a magnetic oxide having a high electrical resistance and can thereby reduce eddy current loss. Thus, the magnetic loss coefficient tan δ/μ at 2 GHz is as small as 0.01, and the magnetic loss coefficient tan δ/μ in the gigahertz band can be reduced. However, the real part of the complex permeability μ′ at 2 GHz is as small as 1.4, and the real part of the complex permeability μ′ in the gigahertz band cannot be increased. That is, high permeability and low magnetic loss are incompatible in the composite magnetic material of Patent Document 1.
Patent Document 2 discloses a magnetic composite material in which magnetic metal particles having a needle shape with an aspect ratio (long axis length/short axis length) of 1.5 to 20 are dispersed in a dielectric material. In the magnetic composite material of Patent Document 2, in a sample whose loss tangent (tan δ) at 3 GHz is as small as 0.014, the permeability μ′ is as small as 1.37, and the permeability μ′ in the gigahertz band cannot be increased. On the other hand, in a sample whose permeability is as large as 1.98, the loss tangent (tan δ) is as large as 0.096, and the loss tangent (tan δ) in the gigahertz band cannot be reduced. That is, high permeability and low magnetic loss are incompatible in the magnetic composite material of Patent Document 2. This is because, in Patent Document 2, magnetic metal particles are dispersed in a dielectric material, such as polyethylene, and are press-molded, so that the ratio of the magnetic particles is as low as 30%, and the magnetic metal particles cannot sufficiently be insulated from each other.
Patent document 1: JP2010238748 (A)
Patent document 2: JP2014116332 (A)
The present invention has been made in view of the above problems. It is an object of the invention to provide a composite magnetic body having high permeability and low magnetic loss in a high-frequency region of gigahertz band and a small high-frequency electronic component with low insertion loss using the composite magnetic body.
As a result of intensive studies on composite magnetic bodies with high permeability and low magnetic loss in the high-frequency region of gigahertz band, the present inventors have found that a composite magnetic body having a higher permeability and a lower magnetic loss than before can be obtained by including magnetic nanowires aligned so as not to intersect each other in the composite magnetic body, and the present invention has been completed. The present inventors have also found that a high-frequency electronic component having a smaller size and a lower insertion loss than before can be obtained by including the composite magnetic body or a magnetic substrate containing the composite magnetic body in the high-frequency electronic component, and the present invention has been completed.
That is, a composite magnetic body of the present invention includes: magnetic nanowires aligned so as not to intersect each other; and an insulator for electrically insulating the magnetic nanowires.
The composite magnetic body according to the present embodiment can have high permeability and low magnetic loss particularly in the high-frequency region of gigahertz band among the high-frequency regions of megahertz band and gigahertz band. Although the mechanism of action by which such an effect is exerted has not been clarified yet, the following mechanism of action can be considered.
That is, in the composite magnetic body according to the present invention, since the magnetic nanowires are aligned so as not to intersect each other, the volume ratio of the magnetic nanowires in the composite magnetic body can easily be increased, and the permeability of the composite magnetic body in the gigahertz band can be increased. In addition, since the magnetic nanowires are electrically insulated by the insulator, the eddy current loss can be reduced, and the magnetic loss in the gigahertz band can be reduced.
Preferably, the magnetic nanowires contain at least one metal of Fe, Co and Ni.
Preferably, a magnetic substrate includes the composite magnetic body.
Further, the high-frequency electronic component according to the present invention includes the composite magnetic body or the magnetic substrate containing the composite magnetic body. In this structure, the deterioration of the characteristics due to the inductor loss is small, and the insertion loss can be reduced particularly in the gigahertz band. Accordingly, it is possible to provide a small and thin high-frequency electronic component with low insertion loss, particularly in the high-frequency region of the gigahertz band, among the high-frequency regions of the megahertz band and the gigahertz band.
Preferably, the composite magnetic body is contained in a magnetic core. In this structure, the insertion loss can be effectively reduced particularly in the gigahertz band.
Preferably, the magnetic core includes a magnetic central leg passing through a coil, and the magnetic nanowires contained in the magnetic central leg are aligned substantially perpendicularly to a winding axis of the coil. In this structure, the magnetic flux passing through the magnetic central leg intersects the magnetic nanowires so as to be substantially orthogonal to their magnetization easy direction (longitudinal direction of the magnetic nanowires). Thus, the eddy current loss particularly in the gigahertz band is reduced, the magnetic loss is reduced, and the insertion loss of the high-frequency electronic component can be reduced.
Preferably, the substrate includes at least one of a magnetic upper substrate disposed above the coil and a magnetic lower substrate disposed below the coil, and the magnetic nanowires contained in at least one of the magnetic upper substrate and the magnetic lower substrate are aligned substantially in parallel to the winding axis of the coil, in this structure, the magnetic flux passing through at least one of the magnetic upper substrate and the magnetic lower substrate intersects the magnetic nanowires so as to be substantially orthogonal to their magnetization easy direction (longitudinal direction of the magnetic nanowires). Thus, the eddy current loss particularly in the gigahertz band is reduced, the magnetic loss is reduced, and the insertion loss of the high-frequency electronic component can be reduced.
Preferably, the magnetic core includes a magnetic outer leg disposed at a periphery of the coil, and the magnetic nanowires contained in the magnetic outer leg are aligned substantially perpendicularly to the winding axis of the coil. In this structure, the magnetic flux passing through the magnetic outer leg intersects the magnetic nanowires so as to be substantially orthogonal to their magnetization easy direction (longitudinal direction of the magnetic nanowires). Thus, the eddy current loss particularly in the gigahertz band is reduced, the magnetic loss is reduced, and the insertion loss of the high-frequency electronic component can further be reduced.
Hereinafter, the present invention is described based on embodiments shown in the figures.
A high-frequency electronic component 1 shown in
The inductors 11, 12, and 17 and the capacitors 13 to 16 are formed by forming a multilayer substrate consisting of a ground layer, an insulating layer, and a conductor layer into the shape as shown in
As shown in
The magnetic central legs 23 and 24 are magnetic cores (cores) having the same shape and function to increase the inductance of the inductors 11 and 12. The magnetic central leg 23 is inserted into the coil portion 110. The magnetic central leg 24 is inserted into the coil portion 120. The magnetic lower substrate 22 constitutes the bottom of the high-frequency electronic component 1. The magnetic upper substrate 21 constitutes the top of the high-frequency electronic component 1.
The magnetic upper substrate 21 and the magnetic lower substrate 22 are magnetic substrates and function to increase the inductance of the inductors 11, 12, and 17. As shown in
As shown in
In the present embodiment, the magnetic central legs 23 and 24 include a composite magnetic body. The magnetic central leg 23 formed by the composite magnetic body includes linear magnetic nanowires 361 aligned so as not to intersect each other and an insulator 365 for electrically insulating the magnetic nanowires 361 from each other. As shown in
Although not illustrated, the magnetic central leg 24 formed by a composite magnetic body also includes linear magnetic nanowires 361 aligned so as not to intersect each other and an insulator 365 for electrically insulating the magnetic nanowires 361 from each other. As shown in
The magnetic nanowires 361 contain at least one metal of Fe, Co, and Ni. More specifically, the magnetic nanowires 361 contain a single metal of Fe, Co, Ni, etc. and an alloy of these metals, such as FeCo alloy, FeNi alloy, CoNi alloy, and FeCoNi alloy. In addition, the magnetic nanowires 361 may contain a FeSi alloy or FeSiCr alloy in which other elements are contained in the above-described metal or alloy. In addition, the magnetic nanowires 361 may contain optional additional elements or unavoidable impurities, such as Cr, Mo, Mn, Cu, Sn, Zn, Al, P, B, and V. The magnetic nanowires 361 made of these metals or alloy's exhibit soft magnetism.
The volume ratio of the magnetic nanowires 361 in the composite magnetic body is preferably 45% or more and 90% or less. When the volume ratio is within the above range, it is possible to prevent the decrease of the real part of the permeability μ′ of the composite magnetic body due to too small volume ratio and to prevent the decrease in insulation between the magnetic nanowires 361 due to too large volume ratio.
Preferably, the magnetic nanowire 361 have a diameter of 5 nm or more and 500 nm or less. When the magnetic nanowire 361 has a diameter in the above range, it is possible to prevent the damage caused by the insufficient strength of the magnetic nanowire 361 due to too small diameter and also prevent the increase in magnetic loss tan δ/μ of the composite magnetic body due to too large diameter.
The length in the longitudinal direction of the magnetic nanowires 361 is not particularly limited, but it is considered that about 1 cm is the upper limit of the length due to the limitation of the method of manufacturing the magnetic wires 361. This is because in the manufacturing method described below, the magnetic nanowires 361 are electrodeposited in holes formed in the insulator 365, and the upper limit of the length of the holes is about 1 cm.
When the magnetic nanowires 361 are formed, the aspect ratio needs to be large. This is because the magnetic loss tan δ/μ of the composite magnetic body can be reduced in the gigahertz band by increasing the shape magnetic anisotropy of the magnetic nanowires 361.
As analyzed by the present inventors, the lower limit of the aspect ratio of the magnetic nanowires 361 is preferably 4, more preferably 20, and particularly preferably 100. The upper limit of the aspect ratio of the magnetic nanowires 361 is 2×106, which corresponds to, for example, the magnetic nanowire 361 whose diameter is 5 nm and whose length is 1 cm.
As analyzed by the present inventors, the ratio d/D of the distance d and the diameter D of the magnetic nanowires 361 is preferably 0.1 to 1, more preferably 0.2 to 0.8, and particularly preferably 0.3 to 0.5.
In the present embodiment, since the magnetic nanowires 361 have a high aspect ratio, unlike Patent Document 2, a forming step for uniformly mixing magnetic metal particles and a resin is not carried out. This is because, for a uniform mixture of a resin and magnetic metal particles, the magnetic metal particles must be particles having a spherical shape or a semi-spherical shape or needle-like particles having a low aspect ratio. While it is practically difficult for the magnetic particles to have a volume ratio of 45% or more by the method of mixing the magnetic metal particles and the resin as shown in Patent Document 2, the present embodiment does not employ such a method and can easily increase the volume ratio of the magnetic nanowires 361 in the composite magnetic body.
The material of the insulator 365 is preferably an oxide or a resin. Examples of the oxide include an Al oxide, a Si oxide, a Cr oxide, a Ta oxide, and an Nb oxide. In particular, the Al oxide is preferably a porous anodic oxide formed by anodic oxidation of Al. This is because this type of porous anodic oxide self-organizingly forms a periodic porous Al oxide having periodic wire-like cavities with nano-level diameter.
Examples of the resin include polystyrene, polybutadiene, polyethylene oxide, polyethylene oxide methyl ether, polyacrylate, polymethacrylic acid ester, polyisoprene, poly N isopropylacrylamide, polybutylmethacrylic acid, polyvinylpyridine, polyferrocenyldimethylsilane, polyferrocenylethylmethylsilane, polydimethylsilane, polyethylene propylene, polyethylene, polytetrabutyl methacrylate, polymethylstyrene, polyhydroxystyrene, epoxy resin, acrylic resin, polyimide resin, polyimide resin, phenol resin, and silicon resin.
Preferably, these resins are combined to form a block copolymer, a two-dimensional periodic structure in which rod-like micelles are hexagonally arranged in a self organizing manner is formed, and the rod-like micelle part is thereafter removed. This forms the insulator 365 having periodic wire-like cavities with nano-level diameter. If necessary, surface treatment agents, such as a coupling agent and a dispersant, and additives, such as a heat stabilizer and a plasticizer, may be added.
In the present embodiment, the magnetic upper substrate 21 and the magnetic lower substrate 22 include a composite magnetic body. The magnetic upper substrate 21 includes linear magnetic nanowires 362 aligned so as not to intersect each other and an insulator 366 for electrically insulating the magnetic nanowires 362 from each other. The magnetic lower substrate 22 includes linear magnetic nanowires 363 aligned so as not to intersect each other and an insulator 367 for electrically insulating the magnetic nanowires 363 from each other.
As shown in
Next, a method of manufacturing the high-frequency electronic component 1 is described. First, an insulator (e.g., the above-mentioned periodic porous Al oxide) composed of a periodic porous structure with a plurality of holes aligned so as not to intersect each other is prepared, and magnetic nanowires are electrodeposited into the holes to form a composite magnetic body. Then, the composite magnetic body is processed into predetermined shape and size to form the magnetic upper substrate 21, the magnetic lower substrate 22, and the magnetic central leg 23. Alternatively, the insulator is previously processed into predetermined shape and size, and magnetic nanowires are electrodeposited in the holes of the insulator to form a composite magnetic body (the magnetic upper substrate 21, the magnetic lower substrate 22, and the magnetic central leg 23).
A circuit pattern substrate on which the inductors 11, 12, and 17 and the capacitors 13 to 16 shown in
Next, the circuit pattern substrate is placed on the upper surface of the magnetic lower substrate 22, and the magnetic central leg 23 is inserted into the opening 111 inside the coil portion 110 shown in
The composite magnetic body (magnetic upper substrate 21, magnetic lower substrate 22, and magnetic central leg 23) according to the present embodiment can have high permeability and low magnetic loss particularly in the high-frequency region of gigahertz band among the high-frequency regions of megahertz band and gigahertz band. Although the mechanism of action by which such an effect is exerted has not been clarified yet, the following mechanism of action can be considered.
That is, in the composite magnetic body according to the present embodiment, since the magnetic nanowires 361, 362, and 363 are aligned so as not to intersect each other, the volume ratio of the magnetic nanowires 361, 362, and 363 in the composite magnetic body can easily be increased, and the permeability of the composite magnetic body in the gigahertz band can be increased. In addition, since the magnetic nanowires 361, 362, and 363 are electrically insulated by the insulators 365, 366, and 367, the eddy current loss can be reduced, and the magnetic loss in the gigahertz band can be reduced.
The high-frequency electronic component 1 according to the present embodiment includes the magnetic upper substrate 21 and the magnetic lower substrate 22 containing the composite magnetic body. Thus, the deterioration of the characteristics due to the inductor loss is small, and the insertion loss can be reduced particularly in the gigahertz band. Accordingly, it is possible to provide a small and thin high-frequency electronic component with low insertion :loss, particularly in the high-frequency region of the gigahertz band, among the high-frequency regions of the megahertz band and the gigahertz band.
In the present embodiment, the composite magnetic body is contained in the magnetic central legs 23 and 24 passing through the inductors 11 and 12. Thus, the insertion loss can be effectively reduced particularly in the gigahertz band.
In the present embodiment, the magnetic nanowires 361 contained in the magnetic central legs 23 and 24 are aligned substantially perpendicularly to the winding axis of the inductors 11 and 12. Thus, the magnetic flux passing through the magnetic central legs 23 and 24 intersects the magnetic nanowires 361 so as to be substantially orthogonal to their magnetization easy direction (longitudinal direction of the magnetic nanowires 361). Thus, the eddy current loss particularly in the gigahertz band is reduced, the magnetic loss is reduced, and the insertion loss of the high-frequency electronic component 1 can be reduced.
In the present embodiment, the magnetic nanowires 362 and 363 contained in the magnetic upper substrate 21 and the magnetic lower substrate 22 are aligned substantially in parallel to the winding axis of the inductors 11 and 12. Thus, the magnetic flux passing through the magnetic upper substrate 21 and the magnetic lower substrate 22 intersects the magnetic nanowires 362 and 363 so as to be substantially orthogonal to their magnetization easy direction (longitudinal direction of the magnetic nanowire 361). Thus, the eddy current loss particularly in the gigahertz band is reduced, the magnetic loss is reduced, and the insertion loss of the high-frequency electronic component 1 can be reduced.
Except for the following matters, a high-frequency electronic component 1A containing a composite magnetic body according to the present embodiment shown in
The magnetic outer legs 25 and 26 are magnetic cores (cores) having the same shape and function to increase the inductance of the inductors 11 and 12. The magnetic outer legs 25 and 26 are rectangular and arranged on the peripheries of the coils 11 and 12.
In the present embodiment, the magnetic outer legs 25 and 26 include a composite magnetic body. The magnetic outer legs 25 and 26 formed by the composite magnetic body include linear magnetic nanowires 364 aligned so as not to intersect each other and an insulator 368 for electrically insulating the magnetic nanowires 364 from each other. As shown in
The magnetic outer legs 25 and 26 can be manufactured by processing the composite magnetic body manufactured by the method described in First Embodiment into predetermined size and shape. The high-frequency electronic component 1A can be manufactured by adding a step of installing the magnetic outer legs 25 and 26 outside the coil portion 110 on the upper surface of the magnetic lower substrate 22 shown in
The same effect as that of the above embodiment can also be obtained in the present embodiment. In addition, in the present embodiment, the magnetic nanowires 364 contained in the magnetic outer legs 25 and 26 are aligned substantially perpendicularly to the winding axis of the coils 11 and 12. Thus, the magnetic flux passing through the magnetic outer legs 25 and 26 intersects the magnetic nanowires 364 so as to be substantially orthogonal to their magnetization easy direction (longitudinal direction of the magnetic nanowires 361). Thus, the eddy current loss particularly in the gigahertz band is reduced, the magnetic loss is reduced, and the insertion loss of the high-frequency electronic component 1 can be further reduced.
The present invention is not limited to the above-described embodiments and can be variously modified within the scope of the present invention.
In the above embodiments, each of the magnetic upper substrate 21, the magnetic lower substrate 22, the magnetic central legs 23 and 24, and the magnetic outer legs 25 and 26 is entirely formed by a composite magnetic body, but each of the magnetic upper substrate 21, the magnetic lower substrate 22, the magnetic central legs 23 and 24, and the magnetic outer legs 25 and 26 may only partially be formed by a composite magnetic body.
The above embodiments describe an example in which the circuit patterns of the inductors 11, 12, and 17 and the capacitors 13 to 16 prepared in advance are installed on the upper surface of the magnetic lower substrate 22 in manufacturing the high-frequency electronic component 1, but the method of manufacturing the high-frequency electronic component 1 is not limited to this example. For example, the coil portion 110 may be formed by laminating a plurality of conductive pastes and insulating pastes on the upper surface of the magnetic lower substrate 22 and connecting them in a coil shape. The inductors 12 and 17 and the capacitors 13 to 16 may also be formed by laminating a plurality of conductive pastes and insulating pastes on the upper surface of the magnetic lower substrate 22.
In the above embodiments, the lengths of the magnetic nanowires 362 and 363 may be shortened as long as the aspect ratio does not become too small, and these may be multilayered and contained in the magnetic upper substrate 21 and the magnetic lower substrate 22. Likewise, the lengths of the magnetic nanowires 361 and 364 may be shortened as long as the aspect ratio does not become too small, and these may be contained in the magnetic central legs 23 and 24 and the magnetic outer legs 25 and 26.
In
The magnetic nanowires 361 to 364 are orderly aligned so as not to intersect each other in the examples shown in
The magnetic nanowires 361 to 364 is substantially linear, but may be slightly distorted (bent) as long as they are insulated without intersecting each other. The magnetic nanowires 361 and 364 are aligned substantially perpendicularly to the winding axis c (Z-axis) of the inductor 11, but may be slightly inclined relative to the vertical line of the winding axis c as long as they are insulated without intersecting each other. That is, the magnetic nanowires 361 and 364 may be inclined relative to the vertical line of the winding axis c (Z-axis) preferably within ±45 degrees, more preferably within ±30 degrees, and particularly preferably within ±15 degrees.
The magnetic nanowires 362 and 363 are aligned substantially in parallel to the winding axis c (Z-axis) of the inductor 11, but may be slightly inclined relative to the winding axis c (Z-axis) as long as they are insulated without intersecting each other. That is, the magnetic nanowires 362 and 363 may be inclined relative to the vertical line of the winding axis c (Z-axis) preferably within ±45 degrees, more preferably within 30 degrees, and particularly preferably within ±15 degrees. When the magnetic nanowires 361 to 364 are inclined at such an inclination angle, it is possible to impart high strength and permeability to the composite magnetic body.
The above-mentioned embodiments show application examples of the present invention to a low pass filter, but the present invention may be applied to other high-frequency electronic components, such as an inductor, a filter, or an antenna usable in a high-frequency region of megahertz band or gigahertz band. More specifically, the present invention may be applied to chip inductors, SAW filters, BAW filters, EMI filters, LTCCs, thin film filters, duplexers, band pass filters, baluns, diplexers, RF front ends, couplers, highly integrated modules for wireless connection and power management, or the like.
Hereinafter, the present invention is described in more detail by way of specific examples, but the present invention is not limited to these examples.
An Al foil was anodically oxidized in a 0.3 M oxalic acid solution at a voltage of 40V to prepare a periodic porous Al oxide having a thickness of 60 μm and a pore diameter of 100 nm. In an electrolyte composed of 1 M ferric sulfate, 0.7 M boric acid, and 1 mM sodium ascorbate maintained at 50 degrees with the cathode being an Al foil connected to the porous Al oxide and the anode being Fe, Fe magnetic nanowires 361 to 363 were electrodeposited in the pores of the periodic porous Al oxide by alternating current electrolysis at 500 Hz. The longitudinal length of the magnetic nanowires 361 to 363 was 21 μm, and the diameter of the magnetic nanowires 361 to 363 was 98 nm. The volume ratio of the magnetic nanowires 361 to 363 determined from the porosity of the periodic porous Al oxide as the insulators 365 to 367 was 51%. Thus, the composite magnetic body of Example 1 formed from the Fe magnetic nanowires 361 to 363 and the Al oxide insulators 365 to 367 was obtained.
When the composite magnetic body was used as the magnetic upper substrate 21, the magnetic lower substrate 22, and the magnetic central legs 23 and 24, a length L of the inductor 11 (an outer diameter of a wire of the coil portion 110 shown in
The magnetic central legs 23 and 24 were formed such that the magnetic nanowires 361 were aligned substantially perpendicularly to the winding axis of the inductors 11 and 12. The magnetic upper substrate 21 and the magnetic lower substrate 22 were formed such that the magnetic nanowires 362 and 363 were aligned substantially in parallel to the winding axis of the inductors 11 and 12.
A vertical groove was dug from the surface using a Ga ion focused ion beam (FIB, FB-2100 manufactured by Hitachi, Ltd.), and the cross section was confirmed by observing the processed surface, that is, the cross-sectional SIM image at an observation angle of 45 degrees. Then, the direction of the magnetic nanowires 361 in the magnetic central legs 23 and 24 and the direction of the magnetic nanowires 362 and 363 in the magnetic upper substrate 21 and the magnetic lower substrate 22 were confirmed.
Further, a circuit pattern substrate was fabricated in which the inductors 11, 12, and 17 and the capacitors 13 to 16 shown in
Next, the circuit pattern substrate was placed on the upper surface of the magnetic lower substrate 22, and the magnetic central leg 23 was inserted into the opening 111 inside the coil portion 110 shown in
The cross section of the composite magnetic body was observed with a scanning electron microscope (SEM) (SU8000 manufactured by Hitachi High-Technologies Corporation) so as to measure the width and length of the magnetic nanowires 361 to 363, and the compositions of the magnetic nanowires 361 to 363 were measured with the attached EDX. The volume ratio of the magnetic nanowires 361 to 363 was determined from the weight of the unit area of the porous insulator, the weight of the magnetic nanowires after electrodeposition, and the specific gravity of the insulators 365 to 367 and the magnetic nanowires 361 to 363.
With a test piece processed into a rod shape of 1 mm×1 mm×80 mm, the real part of the complex permeability μ′ and the magnetic loss tan δ/μ of the composite magnetic body at 2.4 GHz were measured by the perturbation method using a network analyzer (manufactured by HP Agilent Technologies, HP8753D) and a cavity resonator (manufactured by Kanto Electronics Application Development Inc.)
The insertion loss IL of the high-frequency electronic component 1 at 2.4 GHz was measured. Table 1 shows the real part of the complex permeability μ′ and the magnetic loss tan δ/μ of the composite magnetic body at 2.4 GHz, the length L of the inductors 11 and 12 (see
A composite magnetic body and a high-frequency electronic component 1 of Example 2 were produced in the same manner as in Example 1 except that the composite magnetic body was produced in the following manner using a method different from that of Example 1 and were subjected to a similar experiment.
After anodically oxidizing an Al foil in a 0.3 M perchloric acid solution at a voltage of 40 V, the Al foil and the anodic oxidation film in contact with the Al foil were dissolved in a sodium hydroxide solution to prepare a periodic porous Al oxide having a thickness of 70 μm and a pore diameter of 20 nm. An Al sputter deposited layer was formed on one surface of this periodic porous Al oxide to form a cathode. Using Co as an anode, the FeCo alloy magnetic nanowires 361 to 363 were DC electrodeposited into the pores of the periodic porous Al oxide in an electrolyte composed of 0.7 M ferric sulfate, 0.3 M cobalt sulfate, 0.7 M boric acid, and 1 mM sodium ascorbate maintained at 50 degrees. Thereafter, the Al sputter deposited layer was removed in a sodium hydroxide solution. Here, the diameter of the magnetic nanowires 361 to 363 was 19 nm, and the length of the magnetic nanowires 361 to 363 was 60 μm. As a result of composition evaluation by EDX, the composition of the magnetic nanowires 361 to 363 was 64% of Fe and 36% of Co. The volume ratio of the magnetic nanowires 361 to 363 determined from the porosity of the periodic porous Al oxide as the insulators 365 to 367 was 74%. Thus, a composite magnetic body of Example 2 formed from the FeCo alloy magnetic nanowires 361 to 363 and the Al oxide insulators 365 to 367 and the high-frequency electronic component 1 containing this composite magnetic body were obtained.
When the cross section was observed in the same manner as in Example 1, the direction of the magnetic nanowires 361 in the magnetic central legs 23 and 24 and the direction of the magnetic nanowires 362 and 363 in the magnetic upper substrate 21 and the magnetic lower substrate 22 were the same as that of Example 1.
A composite magnetic body and a high-frequency electronic component 1 of Example 3 were produced in the same manner as in Example 1 except that the composite magnetic body was produced in the following manner using a method different from that of Example 1 and were subjected to a similar experiment.
A block copolymer composed of poly (ethylene oxide) methyl ether (molecular weight: 5000) as a hydrophilic block and a polymethacrylate having a polymerization degree of 50 to 150 as a hydrophobic block was synthesized by atom transfer radical polymerization method using copper complex as a catalyst. The obtained block copolymer was represented by the general formula (Formula 1).
CH3(OCH2CH2)mO—CO—C(CH3)2—(C(CH3COOR))n [Formula 1]
Here, m is 80 to 120, n is 50 to 80, and R is an alkyl group.
The obtained 0.02 g block copolymer was mixed with a 0.01 g polyethylene oxide (molecular weight: 400, polymerization degree: 7) and dissolved in chloroform to obtain a 10 wt % solution. This solution was bar-coated on an aluminum foil ultrasonically cleaned with isopropanol so as to have a thickness of 1 μm. Then, a heat treatment was performed at 140° C. for 1 hour, and the hydrophilic block was removed in 0.3 M phosphoric acid-disodium hydrogen phosphate aqueous solution of pH 6.9 to form a periodic porous copolymer film having a thickness of 1 μm and a pore diameter of 10 nm on the Al foil.
Using Co as the anode, the FeCo alloy magnetic nanowires 361 to 363 were DC electrodeposited into the pores of the periodic porous copolymer film in an electrolyte composed of 0.7 M ferric sulfate, 0.3 M cobalt sulfate, 0.7 M boric acid, and 1 nM sodium ascorbate maintained at 50 degrees. Thereafter, the Al foil was removed in a sodium hydroxide solution. Here, the diameter of the magnetic nanowires 361 to 363 was 10 nm, and the length of the magnetic nanowires 361 to 363 was 1 μm. As a result of composition evaluation by EDX, the composition of the magnetic nanowires 361 to 363 was 64% of Fe and 36% of Co. The volume ratio of the magnetic nanowires 361 to 363 determined from the porosity of the periodic porous copolymer film as the insulators was 74%. Thus, a composite magnetic body of Example 3 composed of the FeCo alloy magnetic nanowires 361 to 363 and the periodic porous copolymer film insulators and the high-frequency electronic component 1 containing this composite magnetic body were obtained.
Here, the magnetic central legs 23 and 24 were formed such that the magnetic nanowires 361 were aligned substantially perpendicularly to the winding axis of the inductor 11. The magnetic upper substrate 21 and the magnetic lower substrate 22 were formed such that the magnetic nanowires 362 and 363 were aligned substantially in parallel to the winding axis of the inductor 11.
A composite magnetic body and a high-frequency electronic component 1 of Example 4 were produced in the same manner as in Example 1 except that the composite magnetic body was produced in the following manner using a method different from that of Example 1 and were subjected to a similar experiment.
Insulating layers 341 and 342 were formed on the magnetic lower substrate 22 of Example 1, the coil portions 110 and 120 were formed, and the magnetic central legs 23 and 24 were formed as follows.
That is, a FeCo layer having a thickness of 20 nm was formed by sputtering, a resist ink was printed with a resin mold having a line/space of 20 nm/20 nm, the FeCo layer not printed with the resist ink by reactive ion etching (RIE) was removed, and a 10 nm alumina layer was sputter deposited thereon. This process was repeated to form the magnetic core legs 23 and 24. Thereafter, the magnetic upper substrate 21 covered the magnetic core legs 23 and 24, and the respective parts were bonded with a resin to obtain a composite magnetic body of Example 4 and the high-frequency electronic component 1 containing this composite magnetic body.
When the cross section was observed in the same manner as in Example 1, the direction of the magnetic nanowires 361 in the magnetic central legs 23 and 24 and the direction of the magnetic nanowires 362 and 363 in the magnetic upper substrate 21 and the magnetic lower substrate 22 were the same as that of Example 1.
A composite magnetic body and a high-frequency electronic component 1 of Example 5 were produced in the same manner as in Example 1 except that the composite magnetic body was produced in the following manner using a method different from that of Example 1 and were subjected to a similar experiment.
Nanowires of FeCo alloy were formed on an yttria-stabilized zirconia (YSZ) substrate by CVD using iron chloride and cobalt chloride as evaporation sources and nitrogen gas containing 4% hydrogen as a carrier. The nanowires were taken out and weighed so that the ratio of polyethylene resin was 30 vol %:70 vol %. The above materials were appropriately added with a dispersant and a coupling agent and were kneaded using a mixing roll (No. 191-TM/WM) manufactured by YASUDA SEIKI SEISAKUSHO, LID. The kneading was performed while heating the raw materials to 140° C. until needle-like magnetic particles were homogeneously mixed in the polyethylene resin. Next, the nanowires were aligned by applying a magnetic field to the obtained raw material mixture. Further, this was introduced into a mold heated to 180° C. and molded at a pressure of 35 MPa. Thus, a composite magnetic body of Example 5 and a high-frequency electronic component 1 containing this composite magnetic body were obtained.
When the cross section was observed in the same manner as in Example 1, the direction of the magnetic nanowires 361 in the magnetic central legs 23 and 24 and the direction of the magnetic nanowires 362 and 363 in the magnetic upper substrate 21 and the magnetic lower substrate 22 were the same as that of Example 1.
Except that the direction of the magnetic nanowires 361 in the magnetic central legs 23 and 24 and the direction of the magnetic nanowires 362 and 363 in the magnetic upper substrate 21 and the magnetic lower substrate 22 were reversed from those in Example 5, a composite magnetic body and a high-frequency electronic component 1 of Example 6 were produced in the same manner as in Example 5 and were subjected to a similar experiment. Table 1 shows the results.
A composite magnetic body and a high-frequency electronic component 1 of Comparative Example 1 were produced in the same manner as in Example 1 except that the composite magnetic body was produced as follows by a method different from that of Example 1 and were subjected to a similar experiment.
Using iron oxide (Fe2O3) 73 mol %, cobalt oxide (Co3O4) 18 mo1 %, and barium carbonate (BaCO3) 9 mol % as raw materials, they were weighed so as to have a predetermined composition. Then, the weighed raw materials were blended in a wet ball mill using water as a medium for 16 hours and were thereafter fired at 1250° C. in the air. The magnetic oxide thereby obtained was subjected to dry pulverization for 10 minutes in a vibration mill and was thereafter pulverized in a wet ball mill using water as a medium for 88 hours. Then, the pulverized magnetic oxide was dried at 150° C. for 24 hours to obtain a powder of the magnetic oxide (magnetic oxide powder W) having an average particle size of 1 μm or less. This magnetic oxide had a main component of Co-substituted W-type hexagonal ferrite (BaCo2Fe16O27). Thus, a composite magnetic body of Comparative Example 1 and a high-frequency electronic component 1 containing the composite magnetic body were obtained.
Incidentally, the composite magnetic body of Comparative Example 1 was ferrite and used no nanowires. In Table 1, the columns of the direction of the nanowires were thereby represented as “-”.
A composite magnetic body and a high-frequency electronic component 1 of Comparative Example 2 were produced in the same manner as in Example 1 except that the composite magnetic body was produced as follows by a method different from that of Example 1 and were subjected to a similar experiment.
Fe70Co30 alloy needle-like particles with a major axis length of 45 nm and an aspect ratio of 1.5 and a polyethylene resin as a dielectric material were weighed so that the ratio of the needle-like magnetic particles and the polyethylene resin was 30 vol % 70 vol %. The above materials were appropriately added with a dispersant and a coupling agent and were kneaded using a mixing roll (No. 191-TM/WM) manufactured by YASUDA SEIKI SEISAKUSHO, LTD. The kneading was performed while heating the raw materials to 140° C. until the needle-like magnetic particles were homogeneously mixed in the polyethylene resin. Next, the obtained raw material mixture was introduced into a mold heated to 180° C. and molded at a pressure of 35 MPa. Thus, a composite magnetic body of Comparative Example 2 and a high-frequency electronic component 1 containing this composite magnetic body were obtained.
When the cross section was observed in the same mariner as in Example 1, the direction of the magnetic nanowires 361 in the magnetic central legs 23 and 24 and the direction of the magnetic nanowires 362 and 363 in the magnetic upper substrate 21 and the magnetic lower substrate 22 were random.
As shown in Table 1, in Examples 1 to 6, the real part of the complex permeability μ′ at 2.4 GHz was 2.3 or more, preferably 2.5 or more, and the magnetic loss tan δ/μ was 0.024 or less, preferably 0.022 or less. On the other hand, in Comparative Examples 1 and 2, the real part of the complex permeability μ′ at 2.4 GHz was 2.0 or less, and the magnetic loss tan δ/μ was 0.041 or more. That is, the composite magnetic body according to the present example had a high real part of complex permeability μ′ and a low magnetic loss tan δ/μ in the gigahertz band.
Further, in Examples 1 to 6, the length L of the inductors 11 and 12 was 2150 μm or less, and the insertion loss IL of the high-frequency electronic component 1 was less than 1.00 dB (0.95 dB or less). On the other hand, in Comparative Examples 1 and 2, the length L of the inductors 11 and 12 was larger than 2150 μm, and the insertion loss IL of the high-frequency electronic component 1 was 1.00 dB or more (1.09 dB or more). That is, in the high-frequency electronic component 1 including the composite magnetic body according to the present example, the length L of the inductors 11 and 12 can be reduced, and it is thereby possible to miniaturize the high-frequency electronic component 1 itself and to obtain the high-frequency electronic component 1 having excellent characteristics with a small insertion loss IL. Comparing Examples 1 to 5 with Example 6, it is confirmed that Examples 1 to 5 were more excellent than Example 6 in all items of μ′, tan δ/μ, length L, and IL.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-071727 | Mar 2017 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2018/013771 | 3/30/2018 | WO | 00 |
