Conductors, coils, transformers

Abstract

To suppress an increase in electrical resistance due to eddy current loss caused by the skin effect and the proximity effect occurring in a conducting wire with a highly versatile and simple configuration in a conducting wire suitably used for an electric circuit or an electronic circuit to which a high-frequency current is applied.SOLUTION: A conductor includes at least a first conductor, a second conductor surrounding the first conductor, and a third conductor surrounding the second conductor, and a material having a relative magnetic permeability different from that of the third conductor is used for the first conductor or the second conductor.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a conductor capable of conducting a current containing high-frequency components with low loss, and to a coil and a transformer using the same. [Background technology]

[0002] In recent years, as various mobile information and communication devices such as personal computers, mobile phones, and digital cameras have become smaller, more multifunctional, and have faster processing speeds, their driving frequencies have become higher, and the use of devices that use high-frequency currents has continued to expand.

[0003] For example, demand for devices that use microwave electromagnetic waves, such as satellite communications, mobile communications, and car navigation systems, has grown significantly in recent years, and the spread of electronic toll collection systems (ETC), short-range wireless communications such as wireless LAN, and on-board millimeter-wave radars such as collision prevention radars has also begun. As this trend toward the use of high-frequency currents continues, the frequency of use of high-speed transistors is increasing and circuit operating frequencies are becoming higher than ever before, even in power supply circuits, amplifier circuits, and other circuits included in such circuits.

[0004] When the current flowing through an electric or electronic circuit is increased in frequency, eddy currents are generated in the conductors (conductive wires) inside the circuit due to the magnetic field induced by the high-frequency current. These eddy currents cause an increase in electrical resistance due to the skin effect and proximity effect.

[0005] The skin effect here refers to the phenomenon in which, when an AC current or a current with an AC component flows through a conductor, the magnetic field generated by the AC current causes eddy currents in the conductor, inhibiting current conduction and increasing the resistance of the conductor.The proximity effect refers to the phenomenon in which, when a current flows through a conductor near another conductor, the magnetic field generated by one conductor causes eddy currents in the other conductor, increasing the resistance of the other conductor.

[0006] The current suppression and increased resistance caused by current loss due to the generation of such eddy currents reduce the power conversion efficiency in power conversion circuits and disrupt the voltage and current waveforms in signal transmission lines, degrading the signal waveform. Furthermore, the increased loss and waveform disruption caused by the increased resistance not only cause circuit malfunctions but can also be a factor in circuit destruction. For this reason, there is a need to suppress the generation of eddy currents.

[0007] Furthermore, the increased loss and deterioration of transmission waveforms caused by such high-frequency currents are particularly noticeable in magnetic components. That is, in the case of signal wiring, circuit wiring, and simple electrical conduction, by placing wiring with opposite current polarities and directions opposite to each other, the magnetic fields generated in the opposite directions cancel each other out, suppressing the generation of magnetic fields that cause the skin effect and proximity effect. However, in magnetic components such as coils and transformers, it is not possible to place wiring opposite to each other because the effect of the magnetic field is used.

[0008] These magnetic components generate high magnetic flux densities to increase the inductance of the elements and control the magnetic field. To achieve this, they must use a structure in which conductors are wound closely together in the same direction, which means that the conductors are significantly affected by the skin effect and proximity effect. As a result, the electrical resistance flowing through the conductors of magnetic components reaches several hundred kHz or more, becoming a magnitude that cannot be ignored.

[0009] Furthermore, if a material with a high relative permeability is used as the core material for a magnetic component, the hysteresis characteristics of the BH curve, which shows the relationship between magnetic flux density B and magnetic field H, and the influence of iron loss due to the imaginary part of complex permeability will also be added, raising concerns that the resistance due to the skin effect and proximity effect will be doubled, significantly impairing the operating characteristics of the circuit.

[0010] To address this increased electrical resistance in the conductors of magnetic components, for example, it is possible to shorten the overall length of the conductors of magnetic components by using a magnetic material with a high relative magnetic permeability, or to use an electric wire made by twisting multiple coated electric wires together (litz wire).

[0011] However, when it comes to the relative permeability of magnetic materials, only materials with an extremely low real part of complex permeability are available at frequencies above 1 MHz, making it impossible to shorten the conductor sufficiently, resulting in a non-negligible resistance. Even when materials with a small imaginary part of complex permeability are used, the loss is still very large compared to air-core coils and transformers. Furthermore, even with air-core coils, the skin effect and proximity effect are still large, so currently there are almost no low-loss magnetic components available at frequencies above 1 MHz.

[0012] On the other hand, when using Litz wire, the structure of bundling multiple thin conductors can prevent an increase in resistance due to the skin effect, but the bundling of thin conductors causes losses due to the proximity effect, which means that the resistance suppression effect for high-frequency currents is insufficient. Furthermore, various design know-how is required for the diameter of the wires, the bundling shape, and the insulating material, so a design tailored to the frequency band to be used is essential, resulting in low versatility and high manufacturing costs. Furthermore, even when optimized Litz wire is used, the high-frequency suppression effect is limited to a few MHz, which is an issue.

[0013] Furthermore, for example, Patent Document 1 discloses a coaxial cable having an insulator covering the outer periphery of a central conductor, an outer conductor covering the outer periphery of the insulator, and a sheath covering the outer periphery of the outer conductor, in which the outer conductor is a plastic tape with a conductor layer provided on one side of the plastic tape, which is arranged longitudinally around the outer periphery of the insulator with the conductor layer facing outward, and a sheath tape made of plastic tape as a sheath wound around the conductor layer. Such a coaxial cable is said to be able to improve conductor loss at high frequencies.

[0014] Furthermore, Patent Document 2 describes a method for improving conductor loss by covering a conductor with a material having a higher relative magnetic permeability than the conductor, thereby concentrating the magnetic field in the surrounding magnetic material. [Prior art documents] [Patent documents]

[0015] [Patent Document 1] Japanese Patent Publication No. 2020-42894 [Patent Document 2] Japanese Patent Application Publication No. 2019-009177 Summary of the Invention [Problem to be solved by the invention]

[0016] However, the coaxial cable shown in Patent Document 1 has limitations on the thickness of the conductor layer and the sheath tape in order to achieve the effect of improving conductor loss, and it is necessary to design it to suit the frequency band to be used, which results in low versatility and high manufacturing costs. Furthermore, the conductor covered with a magnetic material shown in Patent Document 2 is effective in suppressing the proximity effect, which is one of the two factors that cause conductor loss: the skin effect and the proximity effect. However, it cannot be said to be a special structure for suppressing the skin effect, and therefore a sufficient suppression effect has not been obtained.

[0017] The present invention aims to provide a conductor suitable for use in electric circuits or electronic circuits to which high-frequency currents, for example, 100 kHz or higher, are applied, which is capable of suppressing an increase in electrical resistance due to eddy current loss caused by the skin effect and proximity effect in the conductor with a highly versatile and simple configuration, and to provide a coil and a transformer using the same. [Means for solving the problem]

[0018] In order to solve the above problems, the present invention proposes the following means. That is, the conductor of the present invention has at least a first conductor, a second conductor surrounding the first conductor, and a third conductor surrounding the second conductor, and is characterized in that the first conductor or the second conductor uses a material having a different relative magnetic permeability than the third conductor.

[0019] According to the present invention, even when a high-frequency current or voltage of, for example, 100 kHz or higher is applied to a conductor, the resistivity of the first conductor and the third conductor is higher than that of the second conductor, and the generation of eddy currents is suppressed. This effectively suppresses increases in electrical resistance due to the skin effect and proximity effect in the conductor. This makes it possible to efficiently propagate high-frequency currents and voltages with little loss.

[0020] In the present invention, an insulating layer may be formed between the first conductor and the second conductor.

[0021] In the present invention, the third conductor may be made of a material having a relative magnetic permeability of 2 or more.

[0022] In the present invention, the third conductor may be made of a material containing a magnetic substance.

[0023] In the present invention, at least one of the first conductor and the second conductor may be made of a material containing at least one of copper, silver, gold, and aluminum.

[0024] The coil of the present invention is characterized in that it is formed by winding the conductor wire described in each of the above items around a magnetic core.

[0025] The transformer of the present invention is characterized in that it is formed by winding the conductor wire described in each of the above items around a magnetic core.

[0026] In addition, in the present invention, the conductor may be composed of a winding having the first conductor and the second conductor wound around the magnetic core, an insulator portion covering the entire winding portion of the winding, and the third conductor covering the insulator portion. [Effects of the Invention]

[0027] According to the present invention, it is possible to provide a conductor suitable for use in electric circuits or electronic circuits to which high-frequency currents, for example, 100 kHz or higher, are applied, which is capable of suppressing an increase in electrical resistance due to eddy current loss caused by the skin effect and proximity effect in the conductor with a highly versatile and simple configuration, as well as a coil and a transformer using the same. [Brief explanation of the drawings]

[0028] [Figure 1] 1 is a cross-sectional view showing a conductor wire according to a first embodiment of the present invention. [Figure 2] FIG. 4 is a cross-sectional view showing a conductor according to a second embodiment of the present invention. [Figure 3] FIG. 10 is a cross-sectional view showing a conductor according to a third embodiment of the present invention. [Figure 4] FIG. 10 is a cross-sectional view showing a conductor according to a fourth embodiment of the present invention. [Figure 5] FIG. 10 is a cross-sectional view showing a conductor according to a fifth embodiment of the present invention. [Figure 6] 1 is an enlarged cross-sectional view showing a main part of a coil according to a first embodiment of the present invention. [Figure 7] FIG. 6 is an enlarged cross-sectional view showing a main part of a coil according to a second embodiment of the present invention. [Figure 8] FIG. 10 is an enlarged cross-sectional view of a main part showing a coil (transformer) according to a third embodiment of the present invention. [Figure 9] FIG. 10 is an enlarged cross-sectional view of a main part showing a coil (transformer) according to a fourth embodiment of the present invention. [Figure 10] 10 is a graph showing the results of an example (verification example) of the conductor of the present invention. [Figure 11] 10 is a graph showing the results of an example (verification example) of the conductor of the present invention. [Figure 12] 10 is a graph showing the results of an example (verification example) of a conventional conductor. DETAILED DESCRIPTION OF THE INVENTION

[0029] The present embodiment will be described in detail below with reference to the drawings as appropriate. The drawings used in the following description may show characteristic portions enlarged for the sake of clarity, and the dimensional ratios of each component may differ from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto. Appropriate changes can be made within the scope of the present invention.

[0030] (Conducting wire: First embodiment) FIG. 1 is a cross-sectional view showing a conductor according to a first embodiment of the present invention. Conductor 10 of this embodiment has, for example, a circular cross section and includes a first conductor (center conductor) 11 formed in a region including the center, a second conductor (central conductor) 12 in contact with the outer peripheral surface of first conductor 11 and formed cylindrically so as to surround first conductor 11, and a third conductor (outer conductor) 13 in contact with the outer peripheral surface of second conductor 12 and formed cylindrically so as to surround second conductor 12. An insulating layer (dielectric layer) may further be formed in contact with the outer peripheral surface of third conductor 13.

[0031] The first conductor 11 and the third conductor 13 are made of a material having a different relative magnetic permeability from that of the second conductor 12. That is, in this embodiment, the first conductor 11 and the third conductor 13 are made of iron (a magnetic material), and the second conductor 12 is made of copper.

[0032] With this configuration, in the conductor 10 of this embodiment, the first conductor 11 and the third conductor 13 have a higher relative magnetic permeability than the second conductor 12. Note that the relative magnetic permeability is the ratio (μ / μ0) of the magnetic permeability μ of an object to the magnetic permeability μ0 in a vacuum, where μ is the proportional constant when the relationship between the strength H of a magnetic field (magnetic field) and the magnetic flux density B is expressed as B=μH.

[0033] The first conductor 11 occupying the central region of the conductor 10 and the third conductor 13 constituting the outermost surface of the conductor 10 may be selected from materials having a relative permeability greater than 2 and electrical conductivity, for example. The first conductor 11 and the third conductor 13 may be made of, for example, iron, an iron alloy, nickel, or a nickel alloy. Examples of iron alloys include FeSi-based alloys (FeSiAl, FeSiAlCr, etc.), FeAl-based alloys (FeAl, FeAlSi, FeAlSiCr, FeAlO, etc.), FeCo-based alloys (FeCo, FeCoB, FeCoV, etc.), FeNi-based alloys (FeNi, FeNiMo, FeNiCr, FeNiSi, etc.) (Permalloy, etc.), FeTa-based alloys (FeTa, FeTaC, FeTaN, etc.), FeMg-based alloys (FeMgO, etc.), FeZr-based alloys (FeZrNb, FeZrN, etc.), FeC-based alloys, FeN-based alloys, FeP-based alloys, FeNb-based alloys, FeHf-based alloys, and FeB-based alloys.

[0034] Furthermore, the constituent materials of the first conductor 11 and the third conductor 13 are not limited to the above-mentioned iron-based materials, but may be, for example, magnetic powder. body( It is also possible to use a material containing iron powder (carbonyl iron powder, R-Fe-N alloy, amorphous iron, etc.), in which case the first conductor 11 and the third conductor 13 may have high resistance so that the conductivity falls within the range of an insulator.

[0035] The second conductor 12 disposed between the first conductor 11 and the third conductor 13 in the conductor 10 may be selected from materials having a relative magnetic permeability of less than 2 and having electrical conductivity, for example. Examples of materials that can be used to form the second conductor 12 include pure copper (0.99), aluminum (1.00), platinum (1.00), silver (0.99), brass (1.00), and gold (1.00). The values ​​in parentheses indicate relative permeability (μ / μ0).

[0036] The ratio (R1:R2:R3) of the length R1 between the first conductor 11 and the second conductor, the length R2 between the second conductor 12 and the third conductor, and the radius R3 of the third conductor 13 to the radius of the entire cross section of the conductor 10 may be, for example, approximately 1:1:0.01 to 1:1:0.5. The lengths R1 and R2 here are determined based on the skin depth calculated from the frequency and conductor material used by the conductor, and it is preferable that R1 and R2 be lengths close to the skin depth.

[0037] According to the conductor 10 of this embodiment as described above, the first conductor 11 and the third conductor 13, which are made of iron and have a higher relative magnetic permeability than the second conductor 12 made of copper, are formed on the center and outer surface sides of the second conductor 12, respectively.As a result, even if a high-frequency current and voltage of, for example, 100 kHz or more is applied to the conductor 10, the magnetic field is concentrated on the first conductor 11 and the third conductor 13, thereby weakening the magnetic field caused by losses in the second conductor 12 and suppressing the generation of eddy currents.

[0038] This effectively suppresses an increase in electrical resistance due to the skin effect and proximity effect in the conductor 10. Therefore, the conductor 10 of this embodiment makes it possible to efficiently transmit high-frequency currents and voltages, for example, of 100 kHz or higher, with little loss.

[0039] Furthermore, the conductor 10 of this embodiment can be formed simply by coating a metal film around a metal solid wire with a circular cross section. Therefore, compared to conventional low-loss electric wires using Litz wire, the structure is simpler and can be manufactured at low cost. Furthermore, there is no need to design it to suit the frequency band to be used, making it possible to realize a highly versatile high-frequency conductor 10.

[0040] In this embodiment, the conductor 10 is formed of three conductor layers: the first conductor 11, the second conductor 12, and the third conductor 13. However, the conductor of the present invention is not limited to this, and the conductor may be formed of four or more conductor layers. In this case, it is preferable that the conductor in the outermost layer be made of a material with a higher relative magnetic permeability than the conductors further inside.

[0041] Furthermore, in this embodiment, an example is shown in which a metal single wire with a circular cross section is used as the first conductor 11, but it may also be formed by twisting together a plurality of thin conductor wires, and is not limited to a single wire.

[0042] (Conducting wire: second embodiment) FIG. 2 is a cross-sectional view showing a conductor according to a second embodiment of the present invention. Note that duplicated explanations of the configurations similar to those of the first embodiment will be omitted. Conductor 20 of this embodiment has, for example, a circular cross section and includes a first conductor (center conductor) 21 formed in a region including the center, an insulator layer 24 in contact with the outer peripheral surface of first conductor 21 and formed cylindrically so as to surround first conductor 21, a second conductor (center conductor) 22 in contact with the outer peripheral surface of insulator layer 24 and formed cylindrically so as to surround insulator layer 24, and a third conductor (outer conductor) 23 in contact with the outer peripheral surface of second conductor 22 and formed cylindrically so as to surround second conductor 22. An insulating layer (dielectric layer) may be further formed in contact with the outer peripheral surface of third conductor 23.

[0043] The third conductor 23 is made of a material having a different relative magnetic permeability from the first conductor 21 and the second conductor 22. That is, in this embodiment, the third conductor 23 is made of iron, and the first conductor 21 and the second conductor 22 are made of copper. With this configuration, in the conductor 20 of this embodiment, the third conductor 23 has a higher relative magnetic permeability than the first conductor 21 and the second conductor 22.

[0044] The insulating layer 24 is made of an insulating material, such as a resin, polyester, polyurethane, polyimide, polyesterimide, or polyamideimide.

[0045] According to the conductor 20 of this embodiment as described above, the generation of eddy currents is suppressed, and the high-frequency currents and voltages can be propagated efficiently with little loss, even when high-frequency currents and voltages of, for example, 100 kHz or higher are applied to the conductor 20. Furthermore, by forming the insulator layer 24 between the first conductor 21 and the second conductor 22, the conductor 20 can be used as a coaxial cable in which different currents and voltages are applied between the first conductor 21 and the second conductor 22 and the third conductor 23. Furthermore, eddy currents can be more effectively suppressed by using the second conductor as the main power transmission line rather than the first conductor 21 in which the signal line is arranged in a conventional coaxial cable.

[0046] (Conducting wire: third embodiment) FIG. 3 is a cross-sectional view showing a conductor according to a third embodiment of the present invention. Note that duplicated explanations of the configurations similar to those of the first embodiment will be omitted. The conductor 30 of this embodiment is an example formed as wiring on a substrate. The conductor 30 formed on one main surface of the substrate P has, for example, a first conductor (center conductor) 31 having a rectangular cross section and formed in a region including the center, a second conductor (center conductor) 32 in contact with the outer peripheral surface of the first conductor 31 and formed in a square cylindrical shape so as to surround the first conductor 31, and a third conductor (outer peripheral conductor) 33 in contact with the outer peripheral surface of the second conductor 32 and formed in a U-shaped cross section so as to surround three sides of the second conductor 32 excluding the side facing the substrate P. With this configuration, the conductor 30 is formed to have a rectangular cross section.

[0047] The first conductor 31 and the third conductor 33 are made of a material having a different relative magnetic permeability from that of the second conductor 32. That is, in this embodiment, the first conductor 31 and the third conductor 33 are made of iron, and the second conductor 32 is made of copper.

[0048] According to the conductor 30 of this embodiment as described above, the generation of eddy currents is suppressed, and the high-frequency currents and voltages can be propagated efficiently with little loss, even when a high-frequency current or voltage of, for example, 100 kHz or more is applied to the conductor 30. Furthermore, by forming the cross section of the conductor 30 into a rectangular shape, it can be formed thin and in close contact with one main surface of the substrate P.

[0049] (Conducting wire: fourth embodiment) FIG. 4 is a cross-sectional view showing a conductor according to a third embodiment of the present invention. Note that duplicated explanations of the configurations similar to those of the first embodiment will be omitted. The conductor 40 of this embodiment is an example formed as wiring on a substrate. The conductor 40 formed on one main surface of the substrate P has, for example, a first conductor (center conductor) 41 having a rectangular cross section and formed in a region including the center, an insulator layer 44 in contact with the outer peripheral surface of the first conductor 41 and formed in a square tubular shape so as to surround the first conductor 41, a second conductor (center conductor) 42 in contact with the outer peripheral surface of the insulator layer 44 and formed in a square tubular shape so as to surround the insulator layer 44, and a third conductor (peripheral conductor) 43 in contact with the outer peripheral surface of the second conductor 42 and formed in a U-shaped cross section so as to surround three sides of the second conductor 42 excluding the side facing the substrate P. With this configuration, the conductor 40 is formed to have a rectangular cross section.

[0050] The third conductor 43 is made of a material having a different relative magnetic permeability from the first conductor 41 and the second conductor 42. That is, in this embodiment, the third conductor 43 is made of iron, and the first conductor 41 and the second conductor 42 are made of copper.

[0051] According to the conductor 40 of this embodiment as described above, even when a high-frequency current and voltage of, for example, 100 kHz or more is applied to the conductor 30, the generation of eddy currents is suppressed, and the high-frequency current and voltage can be propagated efficiently with little loss. Furthermore, by forming the cross section of the conductor 40 into a rectangular shape, it can be formed thin and in close contact with one main surface of the substrate P. Furthermore, by forming an insulating layer 44 between the first conductor 41 and the second conductor 42, the conductor 40 can be used as coaxial wiring to apply different currents and voltages between the first conductor 41 and the second conductor 42 and the third conductor 43.

[0052] (Conducting wire: fifth embodiment) FIG. 5 is a cross-sectional view showing a conductor according to a fifth embodiment of the present invention. Note that duplicated explanations of the configurations similar to those of the first embodiment will be omitted. The conductor 50 of this embodiment is an example formed as a transformer on a substrate. The conductor 50 formed on one main surface of the substrate P has a first conductor 50A (primary side conductor) and a second conductor 50B (secondary side conductor) that are symmetrical to each other with an insulator layer 54 interposed therebetween. Each of the first conductor 50A and the second conductor 50B has a first conductor (center conductor) 51 formed in a region including the center, a second conductor (center conductor) 52 that is in contact with the outer peripheral surface of the first conductor 51 and is formed in a rectangular cylindrical shape so as to surround the first conductor 51, and a third conductor (outer peripheral conductor) 53 that is in contact with the outer peripheral surface of the second conductor 52 and is formed with an L-shaped cross section so as to surround two sides of the second conductor 52 excluding the sides facing the substrate P and the insulator layer 54.

[0053] The first conductor 51 and the third conductor 53 are made of a material having a different relative magnetic permeability from that of the second conductor 52. That is, in this embodiment, the first conductor 51 and the third conductor 53 are made of iron, and the second conductor 52 is made of copper.

[0054] According to the conductor 50 of this embodiment as described above, even when a high-frequency current or voltage of, for example, 100 kHz or more is applied to the conductor 50, the generation of eddy currents is suppressed, and the high-frequency current or voltage can be propagated efficiently with little loss. Furthermore, by forming the cross section of the conductor 50 into a rectangular shape, it is possible to form a thin conductor that is in close contact with one main surface of the substrate P. Furthermore, by forming the first conductor 50A and the second conductor 50B symmetrically across the insulator layer 54, it is possible to form a transformer on the substrate P that has little loss even when a high-frequency current or voltage is applied.

[0055] As can be seen from a comparison of the cross-sectional structures of the first and second embodiments, the first conductor 51 in this embodiment can also be made of the same material as the second conductor 52 or a material with similar magnetic permeability and conductivity, with an insulating layer (corresponding to the insulating layer 24 in the second embodiment) provided in between.

[0056] (Coil: First embodiment) FIG. 6 is an enlarged cross-sectional view of a main part showing one winding of the coil according to the first embodiment of the present invention. The coil 1 of this embodiment is made by winding a conducting wire 60 around a magnetic core 66 . The magnetic core 66 may be made of a magnetic material, such as an electromagnetic steel laminate or a ferrite material.

[0057] Conductor 60 wound around magnetic core 66 has, for example, a rectangular cross section and includes a first conductor (center conductor) 61 formed in a region including the center, a first insulator layer 64 in contact with the outer peripheral surface of first conductor 61 and formed in a square cylindrical shape so as to surround first conductor 61, a second conductor (center conductor) 62 in contact with the outer peripheral surface of first insulator layer 64 and formed in a square cylindrical shape so as to surround first insulator layer 64, a third conductor (outer conductor) 63 in contact with the outer peripheral surface of second conductor 62 and formed in a square cylindrical shape so as to surround second conductor 62, and a second insulator layer 65 in contact with the outer peripheral surface of third conductor 63 and formed in a square cylindrical shape so as to surround third conductor 63. With this configuration, conductor 60 has a rectangular cross section.

[0058] The third conductor 63 is made of a material having a different relative magnetic permeability from the first conductor 61 and the second conductor 62. That is, in this embodiment, the third conductor 63 is made of iron, and the first conductor 61 and the second conductor 62 are made of copper.

[0059] The first insulating layer 64 and the second insulating layer 65 are made of an insulating material such as resin.

[0060] According to the coil 1 of this embodiment as described above, it is possible to effectively suppress the increase in electrical resistance due to the skin effect and proximity effect in the conducting wire 60 wound around the magnetic core 66, thereby realizing a coil 1 that can efficiently generate a high magnetic flux.

[0061] In this embodiment, as can be seen from the conductors of the first and second embodiments, a coil with the same effect can be realized even if the first conductor 61 and the first insulator layer 64 are made of a material with a higher relative permeability than the second conductor, such as the third conductor.

[0062] (Coil: Second embodiment) FIG. 7 is an enlarged cross-sectional view of a main part showing one winding of a coil according to a second embodiment of the present invention. The coil 2 of this embodiment is formed by winding a conductive wire 70 around a magnetic core 76 .

[0063] Conductor 70 wound around magnetic core 76 has, for example, a flat cross section and includes a flat first conductor (center conductor) 71 formed in a region including the center, flat first insulator layers 74 formed on one main surface and the other main surface of first conductor 71, flat second conductors (center conductors) 72 formed on one main surface of each of the first insulator layers 74, a third conductor (outer conductor) 73 formed in a rectangular cylindrical shape so as to surround first conductor (center conductor) 71, first insulator layers 74, and second conductors 72, and a second insulator layer 75 formed in a rectangular cylindrical shape so as to contact the outer peripheral surface of third conductor 73 and surround third conductor 73. With this configuration, conductor 70 has a flat cross section.

[0064] The third conductor 73 is made of a material having a different relative magnetic permeability from the first conductor 71 and the second conductor 72. That is, in this embodiment, the third conductor 73 is made of iron, and the first conductor 71 and the second conductor 72 are made of copper.

[0065] The first insulating layer 74 and the second insulating layer 75 are made of an insulating material such as resin.

[0066] According to the coil 2 of this embodiment as described above, it is possible to effectively suppress the increase in electrical resistance due to the skin effect and proximity effect in the conducting wire 70 wound around the magnetic core 76, thereby realizing a coil 2 that can efficiently generate a high magnetic flux.

[0067] In this embodiment, as can be seen from the conductors of the first and second embodiments, a coil with the same effect can be realized even if the first conductor 71 and the first insulator layer 74 are made of a material with a higher relative magnetic permeability than the second conductor, such as the third conductor.

[0068] (Coil: Third embodiment) FIG. 8 is an enlarged cross-sectional view of a main part showing one winding of a coil according to a third embodiment of the present invention. The coil 3 of this embodiment is used as a transformer, and is made by winding a conducting wire 80 around a magnetic core 86. The magnetic core 86 may be made of a magnetic material, such as an electromagnetic steel laminate or a ferrite material.

[0069] Conductor 80 wound around magnetic core 86 has first conductor 80A (primary conductor) and second conductor 80B (secondary conductor) arranged symmetrically with each other via insulator layer 84. First conductor 80A and second conductor 80B each have a first conductor (center conductor) 81 with a circular cross section formed in a region including the center, a second conductor (central conductor) 82 in contact with the outer circumferential surface of first conductor 81 and formed cylindrically so as to surround first conductor 81, and a third conductor (outer conductor) 83 in contact with part of the outer circumferential surface of second conductor 81 and with insulator layer 84.

[0070] The first conductor 81 and the third conductor 83 are made of a material having a different relative magnetic permeability from that of the second conductor 82. That is, in this embodiment, the first conductor 81 and the third conductor 83 are made of iron, and the second conductor 82 is made of copper.

[0071] According to the coil (transformer) 3 of this embodiment as described above, the increase in electrical resistance due to the skin effect and proximity effect in the conductor 80 wound around the magnetic core 86 can be effectively suppressed, thereby realizing a highly efficient coil (transformer) 3 with little power loss.

[0072] (Coil: Fourth embodiment) FIG. 9 is an enlarged cross-sectional view of a main part showing a coil according to a fourth embodiment of the present invention. The coil 4 of this embodiment is used as a transformer, and has a conductor 90 consisting of a winding 97 having a first conductor 91 and a second conductor 92 wound around a magnetic core 96, an insulator portion 94 that covers the winding portion of the winding 97 in common, and a third conductor 93 that covers the insulator portion 94. The magnetic core 96 may be made of a magnetic material, such as an electromagnetic steel laminate or a ferrite material.

[0073] The windings 97 constituting the conductor 90 are wound so that a first winding 97A (primary wiring) and a second winding 97B (secondary wiring) are adjacent to each other. Each of the first winding 97A and the second winding 97B has a first conductor 91 with a circular cross section formed in a region including the center, and a second conductor 92 that is in contact with the outer periphery of the first conductor 91 and is formed into a cylindrical shape so as to surround the first conductor 91. An insulator portion 94 that covers the wound portions around which the first winding wire 97A and the second winding wire 97B are wound is made of an insulating material such as resin.

[0074] In this embodiment as well, the first conductor 91 and the third conductor 93 are made of a material having a different relative magnetic permeability from that of the second conductor 92. That is, in this embodiment, the first conductor 91 and the third conductor 93 are made of iron, and the second conductor 92 is made of copper.

[0075] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims. [Example]

[0076] The effect of the conductor of the present invention was verified. As a verification method, a simulation of the resistance value of the conductor was carried out using the JMAG simulator manufactured by JSOL Corporation, and the analysis was carried out based on a 3D simulation with a cylindrical solenoid coil of 10 turns and the relative magnetic permeability of the magnetic coil set to 3.0.

[0077] As Verification Example 1, Figure 10 shows the results of a simulation of the resistance value of a coil in which the conductor shown in Figure 1 is wound around a magnetic core (Example of the present invention: relative permeability of the magnetic core = 3). The simulation results shown in Figure 10 confirmed that the frequency dependence of the resistance value remains unchanged even when magnetic cores made of three different magnetic materials (soft magnetic iron, carbon steel, and electromagnetic steel sheet) are used. This indicates that the conductor of the present invention has a wide degree of design freedom in terms of resistance suppression and is very stable. It was also confirmed that the resistance value is significantly lower than that of a conventional conductor (STD coating) made of a solid copper wire with an insulating coating formed on it.

[0078] As Verification Example 2, Fig. 11 shows the simulation results of the resistance value when the relative permeability of the magnetic core in Verification Example 1 is changed (Example of the present invention: relative permeability of magnetic core = 10). The simulation results shown in Fig. 11 confirmed that the frequency dependence of the resistance value using magnetic cores made of three different types of magnetic materials (magnetic soft iron, carbon steel, and electromagnetic steel sheet) does not change even when the relative permeability of the magnetic core is changed.

[0079] Next, the results of a simulation of the resistance value of a coil in which a conventional conductor, a single copper wire coated with an insulating coating, is wound around a magnetic core, are shown in Figure 12 (a conventional example). According to the simulation results using the conventional conductor shown in Figure 12, the higher the frequency, the more variation there is in the resistance value depending on the material of the magnetic coil, confirming that it is necessary to design the conductor configuration depending on the material of the magnetic coil, and that this method lacks versatility. [Explanation of symbols]

[0080] 1...Coil 10...Conducting wire 11...First conductor 12...Second conductor 13...Third conductor

Claims

1. The semiconductor device has at least a first conductor, a second conductor surrounding the first conductor, and a third conductor surrounding the second conductor, A conductor characterized in that the first conductor and the third conductor are made of a material having a higher relative magnetic permeability than the second conductor.

2. The conductor according to claim 1 , wherein the first conductor and the third conductor are made of a material having a relative magnetic permeability of greater than 2.

3. 3. The conductor according to claim 1, wherein the first conductor and the third conductor are made of a material containing a magnetic substance.

4. The conductor according to any one of claims 1 to 3, wherein the first conductor and the third conductor are formed from a material containing at least one of iron, an iron alloy, nickel, and a nickel alloy.

5. 5. The conductor according to claim 1, wherein an insulating layer is formed between the first conductor and the second conductor.

6. A conductor characterized in that the conductor described in any one of claims 1 to 5 is arranged on a substrate and the cross section of the conductor is rectangular.

7. A coil characterized by being formed by winding a conducting wire described in any one of claims 1 to 5 around a magnetic core.

8. A transformer characterized in that the conductor wire described in any one of claims 1 to 5 is wound around a magnetic core.

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