Abstract: In an electronic component having a built-in coil composed of coil conductors with a length of one turn, the inductance value can be increased while suppressing generation of short circuits inside the coil conductors. The electronic component includes a multilayer body formed by stacking a plurality of magnetic layers on top of one another. The built-in coil includes coil conductors and via hole conductors. The coil conductors each have a ring-shaped coil portion having a cut out portion in one side of one corner thereof, and a connecting portion that form an obtuse angle with a side extending from one end portion of the coil portion and is positioned in a region enclosed or surrounded by the coil portion. Via hole conductors connect the plurality of coil conductors to one another.

Abstract: A method for fabricating a carrier with a three-dimensional inductor comprises the steps of providing a substrate having a protective layer; forming a first photoresist layer on the protective layer; patterning the first photoresist layer to form a second opening and a plurality of disposing slots; forming a first metal layer in second opening and disposing slots; removing the first photoresist layer; forming a first dielectric layer on the protective layer; forming a second photoresist layer on the first dielectric layer; patterning the second photoresist layer to form a plurality of slots; forming a second metal layer in slots to form a plurality of inductive portions; removing the second photoresist layer; forming a second dielectric layer on the first dielectric layer; forming a third photoresist layer on the second dielectric layer; patterning the third photoresist layer to form a plurality of slots; and forming a third metal layer in slots.

Abstract: A transformer may include a first and a second continuous single piece multi-turn helical winding, one concentrically received by the other. The turns of the windings are electrically insulated from one another and spaced sufficiently close together to permit inductive coupling therebetween. The turns may be formed of a conductor having a rectangular cross-section, which may, or may not, include an electrically insulative sheath. The single piece multi-turn helical windings may have a continuous or smooth radius of curvature, with no discontinuities or singularities between first and second end terminals. The transformer may be formed by wrapping electrical conductor about a winding form. The transformer may be used in various electrical circuits, for example converter circuits.

Abstract: A three-dimensional inductor is provided. The three-dimensional inductor is disposed in a multi-layered substrate. The multi-layered substrate includes at least a dielectric layer and at least two metal layers. The three-dimensional inductor includes a first coil and a second coil. The second coil is electrically connected to the first coil. The first coil is on a first plane and formed on a first metal layer. The second coil is on a second plane and disposed in a variety of dielectric layers and metal layer. The first plane is not parallel to or is vertical to the second plane such that the magnetic field generated by the first coil and the magnetic field generated by the second coil are not parallel to each other or are vertical to each other.

Abstract: There is provided a method of making two electrically separated inductors using deposition and wet-etching techniques, which inductors are formed by interwinding one of the inductors within the other inductor on the same planar level. In still another aspect of the invention, there is provided a method of making various levels inductors, each level having at least two electrically separated inductors, using deposition and wet-etching techniques. The inductors on each planar level are formed by interwinding one of the inductors within the other inductor, and then stacking these in a preferred manner. In still another aspect, there is provided a manner of connecting together inductors formed according to the above methods in order to achieve various inductor configurations.

Abstract: The invention provides a multi gap inductor core, a multi gap inductor, transformer, and a corresponding manufacturing method and winding. The multi gap inductor core (1; 1?; 1?; 1??), comprises a first plurality of magnetic lamination sheets (2a-2g; 2a?-2m?; 2a?-2n?) made of magnetic core material arranged in a stack and a second plurality of fixing layers (3a-3f; 3a?-3l?; 3a?-3l?) made of a fixing material. Each fixing layer (3a-3f; 3a?-3l?; 3a?-3l?) is arranged between a corresponding pair of adjacent magnetic lamination sheets (2a-2g; 2a?-2m?; 2a?-2n?) and includes mechanical spacer means (4; 4?) which define a gap (G) having a predetermined thickness (d2) between a corresponding pair of adjacent magnetic lamination sheets (2a-2g; 2a?-2m?; 2a?-2n?).

Abstract: The invention provides a flat band winding for an inductor core comprising at least one insulated conductive flat band having a first linear region, a second linear region, and a third linear region, wherein the third linear region is substantially orthogonally connected to said first linear region and to said second linear region such that said first linear region and said second linear region are displaced by a distance and run in parallel or anti-parallel, and wherein said first linear region and said second linear region are wound in opposite directions around the inductor core and around said third region.

Abstract: A method for manufacturing a coil capable of generating a magnetic field known as an intense field when an electric current passes through it. There is formed at least one boss on at least one turn of the coil and at least one recess of a corresponding form in an adjacent turn, such that the boss extends perpendicularly to the recess for absorbing the mechanical stresses caused by the electromagnetic forces and mechanical forces of thermal origin. The coil is capable of generating a magnetic field known as an intense field when an electric current passes through it. The coil includes a tube made of a conductive material and cut out along an overall helicoidal cut-out line. At least one turn of the coil includes at least one boss extending perpendicularly to a recess of a corresponding form in an adjacent turn.

Abstract: An inductive electrical device comprises multiple laminations, each lamination comprising: a generally planar electrically nonconductive substrate that has a central axis normal to its plane, a first surface and a second surface; at least one electrically conductive layer pattern along the first surface in the form of a narrow strip that starts from a first point displaced from the central axis and extends along the first surface about the central axis through a first angle of rotation to a second point; a least one electrically conductive layer pattern along the second surface in the form of a narrow strip that starts from the second point and extends along the second surface about the central axis through a second angle of rotation to at least the first point; an electrically conductive coupling region passing through the substrate proximate the second point that couples the electrically conductive layer pattern along the first surface to the electrically conductive layer pattern along the second surface; w

Abstract: A stacked inductor with combined metal layers is represented in this invention. The stacked inductor includes: a top layer metal coil, and at least two lower layer metal coils, the metal coils being aligned with each other; adjacent metal coils being connected at the corresponding ends through a via; wherein, each of the lower layer metal coils is consisted of plural layers of metal lines which are interconnected. With the same chip area, the stacked inductor of the present invention can achieve higher inductance and Q factor because of the mutual inductance generated from the plural layers of metal lines and the reduced parasitic resistance.

Abstract: A method of constructing a differential inductor having a high self-resonance frequency is provided. In general, a ground point is identified. A first coil having a first and second loop is created such that the first loop is electrically further away from the ground point than the second loop. A second coil having a third and fourth loop are created such that the third loop is electrically further away from the ground point than the second loop. The first coil and the second coil are positioned such that the first loop is positioned as a near neighbor to said fourth loop and said second loop is positioned as a near neighbor to said third loop.

Abstract: A multilayer coil device is formed by alternately stacking a plurality of insulating layers and a plurality of substantially spiral coil patterns. In the multilayer coil device, the number of turns of each of the substantially spiral coil patterns is more than one. Each of the substantially spiral coil patterns has a protrusion protruding toward a center of the substantially spiral coil pattern. The protrusion is located in a specific region where the number of coil pattern portions that cross a virtual line extending radially outward from the center of the coil pattern is smaller than that in another region of the substantially spiral coil pattern. The protrusion is provided as an additional part of a coil pattern portion that is closest to the center of the substantially spiral coil pattern in the specific region.

Abstract: A foldable polymer-based coil structure and a method for fabricating the same are disclosed. The coil structure has metal wirings and interconnections between the wirings. The wirings and connections are embedded by a polymer. The coil structure is foldable in two or more layers. In the folded condition, coils of one layer overlap the coils of another layer. A stackable structure and jigs for aligning the foldable and stackable structures are also disclosed.

Abstract: Disclosed herein are various embodiments of compact coil power transformers configured to provide high voltage isolation and high voltage breakdown performance characteristics in small packages. Compact coil transformers are provided across which power may be transmitted and received by primary and secondary coils disposed on opposing sides of a substrate without high voltage breakdowns occurring therebetween. At least portions of the compact coil transformer are formed of an electrically insulating, non-metallic, non-semiconductor, low dielectric loss material. The compact coil transformers may be formed in small packages using, by way of example, printed circuit boards, flex circuits, lead frames, CMOS and other fabrication and packaging processes.

Abstract: An inductor winding includes first, second, and third arms, a middle portion extending between and connected to at least two of the first, second, and third arms and arranged to support a winding core mounted thereon, and first, second, and third legs extending downwardly from the first, second and third arms, respectively, and arranged to be mounted on a circuit board. The first, second, and third legs are arranged to provide three-point contact with the circuit board, and the inductor winding is arranged to provide a space between a bottom surface of the winding core mounted on the middle portion and an upper surface of electronic components mounted on the circuit board.

Abstract: Embodiments of the invention provide a transformer comprising: a first coil element having a transverse axis along a transverse direction, the first coil element having p turns where p is greater than or equal to 1; and a second coil element having a transverse axis generally parallel to the transverse axis of the first coil element, the second coil element having n turns, where n is greater than or equal to 5p; wherein the first and second coil elements are arranged to provide electromagnetic coupling between the coil elements along a portion of a length of the second coil element in both a transverse direction parallel to the transverse axes and a lateral direction, wherein the lateral direction is a direction normal to the transverse axes.

Abstract: An inductor circuit with high quality (Q) factor includes a primary inductor and a compensation sub-circuit. The compensation sub-circuit is electrically isolated from the primary inductor. The compensation sub-circuit is magnetically coupled with the primary inductor to compensate the loss in the primary inductor.

Abstract: An integrated printed inductor has a set of open petal loops, connected together in series. For a given inductance value higher quality factor and higher frequency value result using an equal chip surface area. With the same fabrication cost and equal occupied area, higher quality factor values at higher frequency can be achieved. The innovative shape is such that secondary mutual coupling effects occur and contribute to increases of overall inductance values. Small current loops arranged as petals corresponding to inductance value LO are connected in series for the inductance value to add up to a higher value. The loops are connected along a circular path to minimize the total chip area occupied. A secondary loop in the center of the inductor results in a stronger magnetic flux and a higher inductance value, due to both self inductance of the secondary loop and mutual inductance of it with the petals.

Abstract: An insulation transformer and a key input circuit having the same are disclosed. The insulation transformer includes: a core having a certain gap; and primary and secondary coils wound on the core. According to the insulation transformer, the operation deficiency of the insulation transformer can be reduced and thus the signal transmission efficiency can be improved. Also, the key input circuit including: an insulation transformer includes a core having a certain gap, and primary and secondary coils wound on the core; a microcomputer connected with the primary coil; and a key input unit connected with the secondary coil and including multiple resistors and switches. According to the key input circuit having the insulation transformer, the reliability of the operation of the key input circuit can be improved and user inconvenience that may be caused by an operation error can be prevented.

Abstract: The installation size of hearing apparatuses and in particular of hearing devices is to be reduced. Provision is thus made for a hearing apparatus with a transmitting facility including an antenna for the wireless, electromagnetic transmission of data and a switching controller including an inductor, which is used to supply energy to the hearing apparatus and the transmitting facility, with the inductor of the switching controller being identical to the antenna of the transmitting facility. This multiple use of the inductor can save on installation space. In order to avoid mutual interference of the transmitting facility and the switching controller, the signals thereof are modulated independently of one another.

Abstract: The present invention relates to a transformer assembly (1) and a process for manufacturing same. The transformer (1) comprises a primary winding (5) wound on a PCB (9) and a secondary winding (7) mounted adjacent to the primary winding. The primary winding comprises a spiral coil, for example of wire or insulated wire, wound on the PCB. Gate drive windings (31, 33) are incorporated in the PCB (9) and there is therefore very close coupling between the primary winding and the gate drive windings. Furthermore, the secondary winding (7) is a center-tapped secondary having two halves. A flux balance winding (13) is provided to connect the two halves of the center-tapped secondary winding (7) and minimize leakage inductance thereby reducing power loss and spiking effects and obviating the need for complex control arrangements.

Abstract: A multilayer electronic component is provided which includes layers composed of different materials and bonded together and which is capable of suppressing the occurrence of delamination at a bonded portion between the layers composed of different materials. A magnetic first layer is composed of a material with relatively high magnetic permeability. A second magnetic layer is composed of a material with relatively low magnetic permeability. Boundary magnetic layers are provided between the two magnetic layers and include a partial magnetic layer composed of the same material as the first magnetic layer and a partial magnetic layer composed of the same material as the second magnetic layer. The partial magnetic layers are provided to be adjacent to each other in the boundary magnetic layers.

Abstract: A reactor coil includes first and second coil elements each formed by edgewise and rectangular winding of one piece of rectangular wire rod in a manner in which the wound rectangular wire rod is stacked rectangularly and cylindrically and, at a winding terminating end point of the first coil element, the rectangular wire rod is bent approximately 90 degrees in a direction opposite to the winding direction of the first coil element so that the rectangular wire rod is stacked in a direction opposite to the stacking direction of the first coil element and is wound edgewisely and rectangularly in a direction opposite to the winding direction of the first coil element to form the second coil element and, as a result, the first coil element and second coil element are aligned in parallel to each other in a continuous state.

Abstract: A spiral structure having at least one planar winding in at least one first conductive level to form at least one inductive element, wherein the winding is surrounded with a conductive plane and at least one track is formed in a second conductive level and has two ends connected by conductive vias to the plane of the first level, at diametrically opposite positions with respect to the center of the winding.

Abstract: An inductor assembly includes a first inductor, a second inductor being magnetically coupled to the first inductor, and a third inductor being magnetically coupled to said first and second inductors. The third inductor may be connected to a variable resistor adapted for adjusting the magnetic coupling between the first and the second inductors by varying a resistance value of said variable resistor.

Abstract: An electronic component includes a coil whose inductance changes in accordance with the magnitude of a current and in which abrupt reduction in the inductance due to magnetic saturation is suppressed. A stack formed by a plurality of stacked first magnetic layers includes a coil formed by coil electrodes connected to one another in the stack. A first nonmagnetic layer is arranged in such a manner as to cut across the coil. When viewed in a stacking direction, a second nonmagnetic layer is formed in a region outside of a region in which the coil is formed. The structure of the second nonmagnetic layer on the upper side of the first nonmagnetic layer in the stacking direction is different from a structure of the second magnetic layer on the lower side of the first nonmagnetic layer in the stacking direction.

Abstract: A laminated inductor includes a laminate having a plurality of insulating layers, a helical coil and first and second external electrodes on an underside of the laminate. The helical coil has coiled electrodes, each coiled up in one turn, and the first and second external electrodes are connected to respective, or corresponding, ends of the helical coil. Each of the coiled electrodes of the helical coil follow a path along the periphery of one of the insulating layers and include first end located in the path and second end located outside the path. The helical coil and the first external electrode are connected to each other by a lead via conductor formed in a space that is enclosed by parts of the coiled electrodes including the first and second ends.

Abstract: A transformer of fully symmetric structure includes a primary coil assembly and a secondary coil assembly. The primary coil assembly includes a plurality of primary coils formed in a plurality of metal layers, and a first interlayer connection unit for connecting the primary coils. The secondary coil assembly includes a plurality of secondary coils formed in the plurality of metal layers, and a second interlayer connection unit for connecting the secondary coils. The primary and secondary coils formed in the same metal layer are concentric and axisymmetric with respect to a diameter line passing through a planar center point. A balanced-unbalanced transformer (balun) is a type of transformer that may be used to convert an unbalanced signal to a balanced one or vice versa. An integrated circuit may include a semiconductor substrate and a transformer. Electrical elements such as transistors may be formed on the semiconductor substrate.

Abstract: A conductive winding structure, the fabricating method thereof, and the magnetic device having the same. The method for fabricating the conductive winding structure includes: (a) providing a mold with a plurality of extension portions and a plurality of protrusions, the plurality of extension portions are connected to each other as a continuous spiral structure, and the plurality of protrusions extend from the plurality of extension portions; (b) performing an electroforming procedure to form a conductive layer on partial surface of the mold; and (c) stripping the conductive layer from the mold, so as to obtain the conductive winding structure.

Abstract: An electronic component capable of obtaining a large inductance value and a high Q value and a method of manufacturing the electronic component are provided. A coil includes a plurality of coil conductors incorporated in a multilayer structure, a plurality of lands provided at the plurality of coil conductors, and a via-hole conductor connecting the plurality of lands. Lead-out conductors are incorporated in the multilayer structure and connect the coil and external electrodes. The plurality of coil conductors form a substantially rectangular loop path in plan view from the z-axis direction by overlapping each other. The plurality of lands protrude toward outside the path at a short side of the path and do not overlap the lead-out conductors in plan view from the z-axis direction.

Abstract: Embodiments of an inductor including a conductive line including at least one turn and an opening positioned within an interior of a region of the conductive line are disclosed. Embodiments of a related method of designing the inductor are also disclosed.

Abstract: A multilayer electronic component that can suppress the formation of projections and depressions on a surface, and an electronic component unit including the multilayer electronic component, are provided. In the multilayer electronic component, coil electrodes (8) having a shape of ring-shaped wiring with a part removed therefrom are electrically connected to each other to constitute a coil (L). Magnetic layers (4) are stacked together with the plurality of coil electrodes (8). The coil electrodes (8a, 8c, 8e) having a radius r1 and the coil electrodes (8b, 8d) having a radius r2 that is smaller than the radius r1 may be alternately arranged in a stacking direction.

Abstract: An entirely integrated EMI filter is based on a flexible multi-layer strip material. An EE or EI core comprises two side pillars and one middle pillar and forms a closed magnetic circuit. The middle pillar has an air gap. A first winding and a second winding respectively are wound around the two side pillars in a same winding direction. The middle pillar is wound with a third winding and a fourth winding, or with only a fifth winding. Passive components (e.g., all passive components) of the EMI filter are integrated into one core so that in its differential mode, insertion loss is significantly reduced, the size and volume are reduced, and the distribution constant of the EMI filter has less impact on the filter's performance.

Abstract: A method of making a semiconductor device and devices thereof are provided. The semiconductor device (100) includes a semiconductor substrate (102) having opposing first and second surfaces (102a, 102b). The device further includes a planar inductor element (104) disposed on said first surface. The planar inductive element (103) comprises a freestanding electrical conductor extending along a meandering path and defining a plurality of windings (104), where the electrical conductor has a width and a height, and where a height-to-width (HW) ratio is substantially greater than 1.

Abstract: A manufacturing method of electronic components includes forming a first insulation layer on a substrate, forming a plurality of passive elements on the first insulation layer, forming a second insulation layer on the passive elements, forming a plurality of conductor layers electrically connected to the respective passive elements, on the outer side of the second insulation layer to be exposed to an upper surface of each electronic component, and forming grooves between the electronic components including the respective passive elements to expose side surfaces of each electronic component and parts of the conductor layers from the side surfaces of each electronic component. The manufacturing method further including plating a plurality of external electrodes on the respective conductor layers exposed to the upper surface and the side surfaces of each electronic component, and cutting the substrate to completely separate into individual electronic components.

Abstract: A low-loss ferrite comprising as main components 46.5-49.5% by mol of Fe2O3, 17-26% by mol of ZnO, 4-12% by mol of CuO, and 0.2% or more and less than 1.2% by mol of CoO, the balance being NiO, and 0.03-1.4% by mass (as SnO2) of Sn based on 100% by mass of the main components, and having an average crystal grain size of 0.7-2.5 ?m, and an electronic device obtained by integrally sintering pluralities of layers of this low-loss ferrite and coil-shaped electrodes formed in the laminate.

Abstract: There is provided a planar transformer having a dual-bobbin structure. The planar transformer includes a core unit including a pair of cores that are electromagnetically coupled to each other, and a bobbin unit including an inner bobbin part and a board part. The inner bobbin part includes a bobbin body having a predetermined volume and having a through hole into which the core is inserted, and a first winding wound around an outer circumferential surface of the bobbin body, and the board part includes at least one board including a board body having a predetermined surface area and having a through hole into which the inner bobbin part and the core are inserted, and a second winding formed on at least one surface of the board body and causing electromagnetic action with the first winding.

Abstract: An integrated circuit includes a substrate and an inductive device on a first side of the substrate. The integrated circuit includes a first ferromagnetic material on a second side of the substrate opposite the first side.

Abstract: A power module located on a conductive substrate including power conversion circuitry. The power conversion circuitry includes a magnetic device and at least one switch. The magnetic device includes a magnetic core having a surface facing the conductive substrate and a conductive clip facing a surface of the magnetic core with ends of the conductive clip electrically coupled to the conductive substrate to cooperatively form a winding therewith about the magnetic core. The power module also includes an encapsulant about the power conversion circuitry.

Abstract: On-chip integrated variable inductors, methods of making and tuning an on-chip integrated variable inductor, and design structures embodying a circuit containing the on-chip integrated variable inductor. The inductor generally includes a signal line configured to carry an electrical signal, a ground line positioned in proximity to the signal line, and at least one control unit electrically coupled with the ground line. The at least one control unit is configured to open and close switch a current path connecting the ground line with a ground potential so as to change an inductance of the signal line.

Abstract: An inductor includes a core substrate including minute column-like electrical conductors extending between a front surface and a back surface of the core substrate. Each column-like electrical conductor is insulated from adjacent column-like electrical conductors by being surrounded by an insulating material. Insulation layers are formed on the front surface and the back surface of the core substrate, respectively. At least two connection electrical conductors extend through each of the insulation layers. Each connection electrical conductor is electrically connected to a plurality of the column-like electrical conductors. Wirings are formed on each of the insulation layers to connect said connection electrical conductors to each other electrically. The wirings, the connection electrical conductors and the column-like electrical conductors are connected to form a coil in a three-dimensional manner.

Abstract: An apparatus is disclosed comprising a transducer, which transducer comprises at least one electrical connection point configured to enable an external electrical connection of the transducer. The transducer further comprises at least one decoupling coil configured to electrically decouple the transducer from the at least one electrical connection point at a frequency above an operating frequency of the transducer. Moreover, a method for assembling the described apparatus is disclosed.

Abstract: A semiconductor transformer provides high frequency operation by forming the primary windings of the transformer around a section of magnetic material that has a hard axis that lies substantially parallel to the direction of the magnetic field generated by the primary windings. The core can also be formed to have a number of sections where the magnetic flux follows the hard axis through each section of the core.

Abstract: [Problems] To provide a planar inductor that can be easily designed in any size without restricting coil characteristics, that supplies the necessary power corresponding to the area when a pair of inductors are placed facing each other to carry out non-contact power transmission, and that has greater design flexibility that allows for setting separation cut-off lines with relative freedom.

Abstract: A coil formed by winding one flat type wire material rectangularly edgewise thereby stacking the rectangularly edgewise wound flat type wire in rectangular tube shape, wherein not only one edge of the coil including the flat type wire including an end portion of start-of-winding thereof but also another edge of the coil including the flat type wire including an end portion of finish-of-winding thereof are formed to be projecting from an outer circumference of the coil.

Abstract: A magnetic induction device (MID) is disclosed. The MID includes a core, and at least one first winding including at least one conductive strip deposited on the core and including at least two turns which are substantially simultaneously shaped. Related apparatus and methods are also disclosed.

Abstract: A terminal structure of a coil device includes a coil having a rectangular conductive wire covered with a dielectric film, and a terminal having a fusing part. An end portion of the wire from the coil has first and second flat surfaces, and the fusing part is electrically connected to these flat surfaces by fusing. The fusing part includes a planar portion surface-contacting a first flat surface, and a folded piece folded in a direction perpendicular to a plane of the planar portion. The end portion is clamped between the planar portion and the folded piece. The folded piece includes a contact surface portion contacting a second flat surface. The contact surface portion includes a stepped portion that increases a deformation amount of a contact area of the second flat surface contacting the stepped portion, compared to an adjacent area of the second flat surface adjacent to the contact area.

Abstract: Optimal operating techniques are disclosed for using coreless printed-circuit-board (PCB) transformers under (1) minimum input power conditions and (2) maximum energy efficiency conditions. The coreless PCB transformers should be operated at or near the ‘maximum impedance frequency’ (MIF) in order to reduce input power requirement. For maximum energy efficiency, the transformers should be at or near the “maximum efficiency frequency” (MEF) which is below the MIF. The operating principle has been confirmed by measurement and simulation. The proposed operating techniques can be applied to coreless PCB transformers in many circuits that have to meet stringent height requirements, for example to isolate the gates of power MOSFET and IGBT devices from the input power supply.

Abstract: Provided herein is a variable inductor, comprising a substrate having a surface layer and an inner layer, a plurality of fixed inductors disposed on the substrate, a signal microstrip line serially connecting the fixed inductors to form a serial fixed inductor, a conductive sheet, a signal input terminal, and a signal output terminal, wherein one end of the serial fixed inductor is connected to the signal input terminal, the other end of the serial fixed inductor is connected to the signal output terminal, and the conductive sheet is for controlling the fixed inductors. The variable inductor of this invention is useful in applications where a given number of inductance values are required, so as to efficiently adjust and obtain the required inductance values.

Abstract: A layered inductor is manufactured by layering “silver-based conductive layers” and “ferrite-based magnetic layers” and simultaneously firing these layers. The conductive layers are via-connected to form a helical coil. A shape of a cross sectional surface of the conductive layer, cut by a plane perpendicular to a longitudinal direction of each of the conductive layers is a substantial trapezoid shape, having an upper base and a lower base. A base angle ? of the trapezoid shape at both ends of the lower base is equal to or greater than 50° and is smaller than or equal to 80°.