Inductors

Abstract

To provide an inductor capable of suppressing the penetration of magnetic powder into the coating of a conducting wire and suppressing deterioration of electrical characteristics.SOLUTION: A conducting wire 21 includes an end surface 21A along the direction perpendicular to a winding axis MJ of a coil conductor, and a side surface 21B along the direction of the winding axis MJ, and in the cross section perpendicular to the length direction of the conducting wire 21, the conducting wire has a coating 25 formed to surround the end surface 21A and the side surface 21B, and the thickness of a coating 25A at the center of the end surface 21A is thicker than the thickness of the coating 25B on the side surface 21B.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an inductor. [Background technology]

[0002] Patent Document 1 discloses an inductor having a coil conductor formed by winding a rectangular conducting wire, an element body containing the coil conductor, and an external electrode formed on the surface of the element body and connected to the coil conductor. In conventional technology, the overall thickness of the coating is increased in order to prevent problems caused by magnetic powder penetrating the coating of the conductor wire during molding of the inductor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-245473 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, increasing the overall thickness of the coating on the conductor wire reduces the number of turns of the coil conductor, which poses the problem of degraded electrical characteristics.

[0005] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide an inductor which prevents problems caused by magnetic powder sticking into the coating of a conductor wire and also prevents deterioration of electrical characteristics. [Means for solving the problem]

[0006] One aspect of the present invention is a coil formed by winding a rectangular conductor wire. The coil has a winding portion and a pull-out portion pulled out from the winding portion. A coil conductor; Contains magnetic powder and resin In an inductor having an element body incorporating the coil conductor and an external electrode formed on a surface of the element body and connected to the coil conductor, the conductor is A conductor;The coil conductor has an end surface along a direction perpendicular to the winding axis of the coil conductor and a side surface along the direction of the winding axis, and the coating is formed so as to surround the end surface and the side surface in a cross section perpendicular to the longitudinal direction of the conductor, the coating being The cable has an insulating layer made of any one of polyurethane resin, polyester resin, epoxy resin, and polyamide-imide resin and in contact with a conductor, and a fusion layer made of polyamide resin and in contact with the insulating layer, The above The conductive wire on the upper and lower surfaces of the winding portion The thickness of the coating at the center of the end face is the thickness of the coating at both end edges of the end face is between 70% and 130% of the thickness of the coating at the side face, and the thickness of the central portion of the end face of the conductor at the top and bottom surfaces of the winding portion is thicker than the thickness of both ends of the end face; It is an inductor. Effect of the Invention

[0007] According to the inductor of the present invention, problems caused by magnetic powder sticking into the coating of the conductor wire can be suppressed, and deterioration of electrical characteristics can be suppressed. [Brief description of the drawings]

[0008] [Figure 1] 1 is a perspective view of an inductor according to an embodiment of the present invention, viewed from above; [Diagram 2] FIG. 2 is a perspective view of the inductor as viewed from the mounting surface side. [Diagram 3] FIG. 2 is a transparent perspective view showing the internal configuration of an inductor. [Figure 4] 1 is a schematic diagram of a manufacturing process of an inductor. [Diagram 5] FIG. 4 is a cross-sectional view of a conducting wire used in a coil conductor. [Figure 6] 1A is a longitudinal cross-sectional view of a coil conductor, and B and C are schematic cross-sectional views of a conductor. [Figure 7] FIG. 2 is an enlarged view of an end face of a conductor wire. [Figure 8] FIG. 13 is a diagram showing the bow shape of the conductor wire. [Figure 9] FIG. 13 is a diagram showing the bow shape of the conductor wire. [Figure 10] FIG. 13 is a diagram showing the bow shape of the conductor wire. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of the inductor according to this embodiment as viewed from the top surface 12 side, and FIG. 2 is a perspective view of the inductor as viewed from the bottom surface 10 side. The inductor of this embodiment is configured as a surface-mount type electronic component and includes an element body 2 having a substantially rectangular parallelepiped shape, which is one embodiment of a substantially hexahedral shape, and a pair of external electrodes 4 provided on the surface of the element body 2.

[0010] Hereinafter, in the element body 2, the first main surface that faces a mounting board (not shown) during mounting is defined as the bottom surface 10, the second main surface opposite the bottom surface 10 is referred to as the top surface 12, a pair of third main surfaces perpendicular to the bottom surface 10 are referred to as end surfaces 14, and a pair of fourth main surfaces perpendicular to the bottom surface 10 and the pair of end surfaces 14 are referred to as side surfaces 16. 1, the distance from the bottom surface 10 to the top surface 12 is defined as the thickness T of the element body 2, the distance between a pair of side surfaces 16 is defined as the width W of the element body 2, and the distance between a pair of end surfaces 14 is defined as the length L of the element body 2. In addition, the direction of the thickness T is defined as the thickness direction DT, the direction of the width W is defined as the width direction DW, and the direction of the length distance is defined as the length direction DL. The size of the inductor is, for example, a length L of 3.5 mm, a width W of 2.5 mm, and a thickness T of 1.9 mm.

[0011] FIG. 3 is a transparent perspective view showing the internal configuration of the inductor. The element body 2 includes a coil conductor 20 and a substantially hexahedral core 30 in which the coil conductor 20 is embedded, and is configured as a conductor-enclosed magnetic component in which the coil conductor 20 is enclosed in the core 30.

[0012] The core 30 is a molded body obtained by compression molding a mixture of magnetic powder and resin into a substantially hexahedral shape by applying pressure and heat while the coil conductor 20 is contained therein.

[0013] The magnetic powder of this embodiment contains two types of particles: the first magnetic particles, which are large particles with a relatively large average particle size, and the second magnetic particles, which are small particles with a relatively small average particle size. As a result, during compression molding, the second magnetic particles, which are small particles, enter between the first magnetic particles, which are large particles, together with the resin, thereby increasing the filling rate of the magnetic particles in the core 30 and also increasing the magnetic permeability. In this embodiment, the average particle sizes of the metal particles of the first magnetic particles and the second magnetic particles are 24.4 μm and 4.0 μm, respectively. The average particle size of the first magnetic particles is preferably 19 μm or more and 30 μm or less, and the average particle size of the second magnetic particles is preferably 3 μm or more and 5 μm or less. The blending ratio of the large particles to the small particles is 75:25 by weight. The blending ratio of the large particles to the small particles is 70:30 to 85:15 by weight, preferably 70:30 to 80:20 by weight. The ratio of the average particle size of the large particles to the small particles is 5.0 or more. The minimum particle size of the large particles / the maximum particle size of the small particles is, for example, 21.4 / 4.25. The magnetic powder may include particles different from the first magnetic particles and the second magnetic particles.

[0014] In this embodiment, the first magnetic particles and the second magnetic particles are both particles having a metal particle and an insulating film covering the surface of the metal particle with a thickness of several to several tens of nanometers, the metal particle is made of Fe-Si amorphous alloy, and the insulating film is made of zinc phosphate glass. By covering the metal particle with the insulating film, the insulation resistance and the withstand voltage are increased.

[0015] In the first and second magnetic particles, the metal particles may be Fe-Si-Cr alloy powder, Cr-less Fe-Si alloy powder, Fe-Ni-Al alloy powder, Fe-Cr-Al alloy powder, Fe-Si-Al alloy powder, Fe-Ni alloy powder, or Fe-Ni-Mo alloy powder. The second magnetic particles may be made of pure iron such as carbonyl iron powder.

[0016] In addition, in the first magnetic particles and the second magnetic particles, the insulating film may be made of other phosphates (magnesium phosphate, calcium phosphate, manganese phosphate, cadmium phosphate, etc.) or resin materials (silicone-based resins, epoxy-based resins, phenol-based resins, polyamide-based resins, polyimide-based resins, polyphenylene sulfide-based resins, etc.).

[0017] In the mixed powder of the present embodiment in which the soft magnetic powder and the resin are mixed, the resin material is an epoxy resin mainly composed of bisphenol A type epoxy resin. The epoxy resin may be a phenol novolac type epoxy resin. The weight ratio of the resin is 2.9 to 3.1 wt% based on the total weight of the soft magnetic powder and the resin. The resin material may be other than epoxy resin, and may be two or more types instead of one type. For example, the resin material may be a thermosetting resin such as phenol resin, polyester resin, polyimide resin, polyolefin resin, etc., in addition to epoxy resin.

[0018] 3, the coil conductor 20 includes a winding portion 22 around which a conductor wire is wound, and a pair of lead-out portions 24 drawn out from the winding portion 22. The winding portion 22 is formed by winding a conductor wire in a spiral shape such that both ends of the conductor wire are drawn out to the outer periphery of the winding portion 22 and connected to each other at the inner periphery. Inside the element body 2, the coil conductor 20 is embedded in the core 30 with the winding axis of the winding portion 22 oriented along the thickness direction DT of the element body 2. The lead-out portions 24 are drawn out from the winding portion 22 to each of a pair of end faces 14 and are electrically connected to the external electrodes 4.

[0019] The external electrode 4 is a so-called five-surface electrode that is provided over the entire end face 14 and over a portion of each of the bottom face 10, the top face 12, and a pair of side faces 16 adjacent to the end face 14, and is electrically connected to the wiring of the circuit board by an appropriate mounting means such as solder.

[0020] Inductors with such a configuration can improve the DC superposition characteristics by using soft magnetic powder for the magnetic powder, and are therefore used as electronic components in electric circuits through which large currents flow, as choke coils in DC-DC converter circuits and power supply circuits, and as electronic components in electronic devices such as personal computers, DVD players, digital cameras, TVs, mobile phones, smartphones, car electronics, medical and industrial machinery, etc. However, the uses of inductors are not limited to this, and they can also be used, for example, in tuning circuits, filter circuits, rectifying and smoothing circuits, etc.

[0021] In the inductor, an element protection layer may be formed on the entire surface of the element 2 excluding the area of ​​the external electrodes 4. The material for the element protection layer may be, for example, a thermosetting resin such as epoxy resin, polyimide resin, or phenolic resin, or a thermoplastic resin such as polyethylene resin or polyamide resin. These resins may further contain a filler including silicon oxide, titanium oxide, or the like.

[0022] FIG. 4 is a schematic diagram of the manufacturing process of an inductor. As shown in the figure, the inductor manufacturing process includes a coil conductor forming step, a preform forming step, a thermoforming and curing step, a barrel polishing step, and an external electrode forming step.

[0023] The coil conductor forming process is a process for forming the coil conductor 20 from a conductive wire. In this process, the coil conductor 20 is formed into a shape having the above-mentioned winding portion 22 and a pair of lead-out portions 24 by winding the conductive wire in a manner called "alpha winding". The alpha winding refers to a state in which the conductive wire, which functions as a conductor, is wound in two stages in a spiral shape such that the lead-out portions 24 at the start and end of the winding are located on the outer periphery. The number of turns of the coil conductor 20 is not particularly limited.

[0024] The preform forming step is a step of molding a preform called a tablet. The preform is formed by pressing the above-mentioned mixed powder, which is the material of the base body 2, into a solid form that is easy to handle. In this embodiment, two types of tablets are formed: a first tablet of an appropriate shape (e.g., E-shaped) having a groove into which the coil conductor 20 fits, and a second tablet of an appropriate shape (e.g., I-shaped or plate-shaped) that covers the groove of the first tablet.

[0025] In the thermoforming and curing process, the first tablet, the coil conductor, and the second tablet are set in a molding die, and while applying heat, pressure is applied in the overlapping direction of the first tablet and the second tablet, and they are cured to integrate the first tablet, the coil conductor, and the second tablet. This forms the element body 2 in which the coil conductor 20 is enclosed in the core 30.

[0026] The barrel polishing step is a step of barrel polishing this molded body, and by this step, the corners of the element body 2 are rounded.

[0027] The external electrode forming step is a step of forming the external electrodes 4 on the core 30, and includes a surface treatment step, a conductive resin layer forming step, and a plating layer forming step.

[0028] The surface treatment process is a process of modifying the surface of the planned electrode portion by irradiating the electrode portion on the surface of the core 30 with a laser beam. Here, the planned electrode portion refers to the area of ​​the surface of the core 30 where the external electrode 4 is to be formed, including the portion where the lead-out portion 24 is exposed. Specifically, by irradiating the laser beam, the resin on the surface of the core 30 is removed in the area of ​​the planned electrode portion, and the insulating film on the surface of the magnetic particles exposed from the core 30 is removed. As a result, the exposed area of ​​the metal of the magnetic particles per unit area of ​​the surface of the core 30 is larger in the planned electrode portion of the surface of the core 30 than in other surface portions of the core 30. Note that after the laser irradiation, a cleaning process (e.g., an etching process) may be performed to clean the surface of the planned electrode portion.

[0029] In the conductive resin layer forming process, a conductive resin paste containing conductive powder and resin is applied to the electrode locations, and then dried and hardened to form a conductive resin layer. Specifically, the core 30 is dipped from the end face 14 side into the conductive resin paste and pulled up, so that the conductive resin is applied to the desired application range including the end face 14.

[0030] Since such a conductive resin layer contains conductive powder, a uniform potential distribution can be formed at the intended electrode locations in the plating layer formation process described below, thereby improving the homogeneity of the plating layer formed on the conductive resin layer.

[0031] In this embodiment, a mixture of fine silver (Ag) powder (so-called nano silver) with a particle size of several tens of nm and acrylic resin is used as the conductive resin. The weight ratio of silver in the mixture is, for example, 88%. By using such fine silver powder, in addition to improving the homogeneity of the plating layer as described above, the filling rate of silver in the conductive resin layer can be increased to reduce the DC resistance between the external electrode 4 and the lead portion 24.

[0032] In the plating layer forming step, a plating layer is formed on the surface of the conductive resin layer. The plating layer is composed of a first plating layer formed directly on the surface of the conductive resin layer and a second plating layer formed on the first plating layer. In this embodiment, the first plating layer is a nickel (Ni) plating layer having a thickness of 4.0 μm to 15 μm, and the second plating layer is a tin (Sn) plating layer having a thickness of 4 μm to 8 μm. The plating layer may be formed by electrolytic plating (e.g., barrel plating). Note that a copper (Cu) plating layer may be used instead of the nickel (Ni) plating layer. In this embodiment, the plating layer is composed of two layers, but is not limited to this and may be composed of any number of layers.

[0033] By the above external electrode forming step, external electrodes 4 each composed of a conductive resin layer and a plating layer are formed. The external electrodes 4 may be formed only of a plating layer, or may be formed by sputtering, using a copper plate, etc. The external electrodes 4 are not limited to five-sided electrodes, and may be so-called L-shaped electrodes formed only on both the end faces 14 and the bottom face 10, or may be so-called bottom electrodes formed only on the bottom face 10.

[0034] FIG. 5 is a cross-sectional view of a conducting wire 21 used in the coil conductor 20. As shown in FIG. Conductive wire 21 has a rectangular cross-sectional shape. By using a rectangular wire material, conductive wire 21 can be wound without gaps. Conductive wire 21 has a pair of end faces 21A and a pair of side faces 21B. The pair of end faces 21A are surfaces that are perpendicular to winding axis MJ of coil conductor 20, and the pair of side faces 21B are surfaces that are parallel to winding axis MJ. The conductor 21 is a copper-clad aluminum conductor or an aluminum conductor. The conductor 21 includes a pair of side faces 21B and a pair of end faces 21A, and in a cross section perpendicular to the longitudinal direction of the conductor 21, the surface thereof is covered with a coating 25 so as to surround the end faces 21A and the side faces 21B. In addition, in order to connect the lead-out portion 24 of the coil conductor 20 to the external electrode 4, the coating 25 of the conductor 21 is removed from a region of the lead-out portion 24 of the coil conductor 20 that is to be connected to the external electrode 4. In addition, coating 25 on end face 21A has a mushroom shape with a thicker thickness T1 at center P1 of end face 21A and a thinner thickness T3 at both end portions P3 of end face 21A. Coating 25 is divided into an insulating layer and a fusion layer on the outside of the insulating layer, and when coil conductor 20 is formed, the fusion layer melts to fix adjacent conductive wires 21 to each other at winding portion 22 of coil conductor 20, and the thickness of coil conductor 20 at winding portion 22 is about half of its original thickness. Examples of the insulating layer include polyurethane resin, polyester resin, epoxy resin, and polyamideimide resin, and polyamideimide resin is preferred. Examples of the adhesive layer include polyamide resin.

[0035] The thickness T1 of the coating 25A at the center P1 of the end face 21A is thicker than the thickness T2 of the coating 25B at the side face 21B, and the thickness ratio is 150%. Also, the thickness T3 of the coating 25A at both end edges P3 of the end face 21A is thicker than the thickness T2 of the coating 25B at the side face 21B, and the thickness ratio is 130%.

[0036] FIG. 6A is a vertical cross-sectional view of a coil conductor 20, and FIGS. 6B and 6C are schematic cross-sectional views of a conductive wire 21. As shown in FIG. The coil conductor 20 includes a winding portion 22 in which a conductive wire 21 is wound in a spiral shape across two upper and lower stages, and a pair of lead-out portions 24 led out from the winding portion 22. In this figure, the conductive wire 21 is deformed into a bow shape.

[0037] The reason why the conductor 21 is deformed into a bow shape will be explained. As shown typically in FIG. 6B, when coating 25A on end face 21A protrudes outward more than coating 25B on side face 21B, when conductive wire 21 is wound around a winding shaft of a winding machine (not shown), a gap δ is generated in the region between conductive wires 21, as shown typically in FIG. 6C. As the number of turns of conductor 21 increases, conductor 21 becomes tighter. The upper and lower ends of conductor 21 are held by coating 25A, but because there is a gap δ between conductors 21, stress is applied to the center of side surface 21B of conductor 21. As a result, the center of side surface 21B of conductor 21 is depressed, and conductor 21 is deformed into a bow shape, as shown in Fig. 6A.

[0038] FIG. 7 is an enlarged view of end surface 21A of conductive wire 21. As shown in FIG. The magnetic powder of this embodiment includes first magnetic particles 50 having a relatively large average particle size and second magnetic particles 51 having a relatively small average particle size. In coating 25A on end face 21A of conductive wire 21, portions TS where the magnetic particles have penetrated can be seen. If the magnetic powder penetrates, the insulation of the conductor 21 will be reduced, and it will be necessary to improve the withstand voltage of the insulating layer of the coating 25 .

[0039] Table 1 shows the experimental results. [Table 1]

[0040] Samples No. 1 to No. 4 are samples formed by winding a conducting wire 21 manufactured by Furukawa Magnet Wire Corporation to form a coil conductor 20 and embedding the coil conductor 20 in the element body 2. In the element 2, the large first magnetic particles 50 of the metal magnetic powder have an average particle size of 24.4 μm, and the small second magnetic particles 51 have an average particle size of 4.0 μm. The relationship between the metal magnetic powder and the resin is (weight of resin) / (total weight of metal magnetic powder and resin)=3 wt %. The molding pressure for the element is 50Mpa (approximately 500kgf / cm2). The conductor wire 21 is, for example, AILOCKT-FAR BK manufactured by Furukawa Magnet Wire Corporation. Referring to FIG. 5, the rectangular wire has a height H of 0.550 mm, a width W of 0.041 mm, and the material of the coating 25 is polyamideimide resin. In sample numbers 1 to 4, the thickness of the coating 25 was changed by preparing conductors with different thicknesses of the coating 25 manufactured by Furukawa Magnet Wire Corporation.

[0041] The thickness of the coating 25 was measured by cutting the element body 2 in a direction perpendicular to the bottom surface 10 of the element body 2, passing through the winding axis MJ of the winding portion 22 of the coil conductor 20 when viewed from the top surface of the element body 2, and along the longitudinal direction DL of the element body 2, and observing a cross section of one of the conductor wires 21 at the outermost circumference of the step close to the bottom surface 10 of the element body 2 of the winding portion 22 that is wound in two steps, and measuring the thickness of the coating 25 attached to the conductor wire 21 in that cross section. The thickness of coating 25A is the average value of measurements of a thickness T1 at a center P1 of end face 21A of conductive wire 21 close to bottom face 10 of element body 2, and the thicknesses at two locations spaced a predetermined distance apart around center P1 within a range that is 80% of the length of end face 21A centered on center P1. The thickness of coating 25B is the average value of measurements of a thickness at a center P2 of side face 21B of conductive wire 21 close to the side face of element body 2, and the thicknesses at four locations spaced a predetermined distance apart around center P2 within a range that is 80% of the length of side face 21B centered on center P1. The coating thickness C at both ends of the end face 21A is the average value of the thickness at point P3 where the end face 21A of the conductor 21 intersects with the side face 21B adjacent to the side face of the element body 2, and the thicknesses at two points spaced a predetermined distance apart from P3, within a range of 20% of the length of the end face 21A and within a range of 20% of the length of the side face 21B, centered on P3.

[0042] It has been found that when the thickness of the coating is constant, the breakdown voltage (V) tends to decrease as the penetration of magnetic powder into the coating increases (see Figure 7). As shown in Table 1, instead of evaluating the degree to which the magnetic powder penetrates, the change in breakdown voltage (V) is measured.

[0043] The experimental results showed that when A / B was greater than 100% and less than 150%, and C / B was greater than 73% and less than 130%, there was no reduction in the withstand voltage (V) compared to the withstand voltage of 160 (V) of a conventional inductor using conductors with equal thicknesses for A, B, and C. Therefore, it is possible to reduce problems caused by magnetic powder penetration without reducing the inductance value.

[0044] In the coil conductor forming process, the conductive wire 21 of the coil conductor 20 is deformed into an arch shape (see FIG. 6A). 8 to 10 show part of a cut surface of element body 2. This cut surface is obtained by cutting element body 2 in the thickness direction along an imaginary line that passes through winding axis MJ of coil conductor 20 and extends in the longitudinal direction of the top surface of element body 2.

[0045] Table 2 shows the experimental results. [Table 2]

[0046] Sample No. 5 to Sample No. 7 in Table 2 correspond to Figures 8 to 10, respectively, and the bow shape was determined by visually checking the cut surface of element body 2, and those with small deformation were considered to be good. Also, those in which the upper and lower ends of side surface 21B of conductor 21 have moved toward the outer periphery of winding portion 22 and central portion P2 of side surface 21B of conductor 21 has recessed toward the inner periphery of winding portion 22 were considered to be acceptable. Sample No. 5 has a C / B of 73% or more and 130% or less, and as shown in Fig. 8, the deformation of the conductor 21 is small and good. Sample No. 6 has a C / B of 150%, and as shown in Fig. 9, the deformation is greater than that of the sample in Fig. 8, with the upper and lower ends of the side surface 21B of the conductor 21 moving toward the outer periphery of the winding portion 22 and the central portion P2 of the side surface 21B of the conductor 21 recessed toward the inner periphery of the winding portion 22. Sample No. 7 has a C / B of 600% or more, and as shown in Fig. 10, the deformation is greater than that of the sample in Fig. 9, with the upper and lower ends of the side surface 21B of the conductor 21 moving toward the outer periphery of the winding portion 22 and the central portion P2 of the side surface 21B of the conductor 21 recessed toward the inner periphery of the winding portion 22 in both the upper and lower stages of the winding portion 22.

[0047] In the experiment, the molding pressure of the element body 2 was 50 MPa (approximately 500 kgf / cm 2 ). The molding pressure of the element body 2 was changed to Condition 1 to Condition 7. Condition 1 = 546.4 (kgf / cm2), Condition 2 = 521.3 (kgf / cm2), Condition 3 = 496.3 (kgf / cm2), Condition 4 = 397.7 (kgf / cm2), Condition 5 = 299.2 (kgf / cm2), Condition 6 = 198.9 (kgf / cm2), Condition 7 = 148.7 (kgf / cm2).

[0048] It was found that even when the molding pressure was changed to Condition 1 to Condition 7, the withstand pressure (V) of Sample No. 1 to Sample No. 4 did not change. It was found that in coating 25, when A / B is greater than 100% and less than 150%, and C / B is greater than or equal to 73% and less than 130%, there is little decrease in the withstand voltage (V), and the problem of magnetic powder penetration can be reduced without decreasing the inductance value.

[0049] In this embodiment, when the thickness of coating 25A at the center of end face 21A is thicker than the thickness of coating 25B on side face 21B, no decrease in the withstand voltage (V) is observed, and therefore the problem of magnetic powder sticking into conductor 21 in the thermal molding and curing process shown in Fig. 4 can be reduced without reducing the inductance value. An inductor with such a configuration improves the DC bias characteristics by using soft magnetic powder for the magnetic powder, and can reduce problems caused by the soft magnetic powder sticking into conductor 21.

[0050] Furthermore, when the thickness of coating 25A at the center of end face 21A is greater than 100% and less than 150% of the thickness of coating 25B on side face 21B, and the thickness of the coating at both ends of end face 21B is greater than 70% and less than 130% of the thickness of the coating on the side faces, when winding wire 21 around a winding shaft of a winding machine (not shown), unlike the cases shown in Figures 6B and 6C, the size of gap δ between wires 21 does not become so large, improving the bow shape of wire 21. In addition, gap-free winding can be easily performed in the coil conductor forming process shown in Figure 4, so that the number of turns of coil conductor 20 is not reduced and degradation of electrical characteristics can be prevented.

[0051] In this embodiment, it is desirable that the thickness T1 of the coating 25A on the upper and lower end faces 21A be greater than 100% and equal to or less than 150% of the thickness T2 of the coating 25B on the side face 21B. In this embodiment, the thickness T1 of the coating 25A on the upper and lower end faces 21A is made thicker, but the thickness T1 of the coating 25A on either one of the end faces 21A may be made thicker.

[0052] In this embodiment, the thickness of coating 25A in the center of end face 21A may be greater than the thickness of coating 25B in the center of side face 21B. Furthermore, the thickness of coating 25A in the center of end face 21A may be greater than 100% and less than or equal to 150% of the thickness of coating 25B in the center of side face 21B. The thickness of the coating 25A at both edge portions of the end face 21A may be 70% or more and 130% or less of the thickness of the coating 25B at the center portion of the side face 21B.

[0053] The present disclosure provides the following advantages.

[0054] In an inductor having a coil conductor formed by winding a flat rectangular conductor wire, an element body incorporating the coil conductor, and an external electrode formed on the surface of the element body and connected to the coil conductor, the conductor wire includes an end face along a direction perpendicular to the winding axis of the coil conductor and a side face along the direction of the winding axis, and in a cross section perpendicular to the longitudinal direction of the conductor, has a coating formed to surround the end face and the side face, and the thickness of the coating at the center of the end face is thicker than the thickness of the coating on the side face. According to the present disclosure, the thickness of the coating on the end faces is greater than the thickness of the coating on the side faces, thereby reducing problems caused by magnetic powder sticking in and improving pressure resistance. Furthermore, since the thickness of the coating on the side surface can be made thin, the number of turns of the coil conductor is not reduced, and deterioration of the electrical characteristics can be suppressed.

[0055] The thickness of the coating at the center of the end face is greater than 100% and less than 150% of the thickness of the coating at the side face, and the thickness of the coating at both end edges of the end face is greater than 70% and less than 130% of the thickness of the coating at the side face. According to the present disclosure, the thickness of the coating at the center of the end face is greater than 100% and less than 150% of the thickness of the coating at the side faces, and the thickness of the coating at both end edges of the end face is greater than 70% and less than 130% of the thickness of the coating at the side faces, thereby making it possible to adjust the degree of bowing of the conductor.

[0056] The coating on the end surface of the conductor is thicker at the center of the end surface and thinner at both ends of the end surface. According to the present disclosure, the coating on the end face of the conductor is thicker in the center of the end face and thinner at both ends of the end face. Therefore, by adjusting the ratio of the thickness of the center of the end face to the thickness of both ends of the end face, it is possible to adjust the degree of bowing of the conductor while reducing problems caused by magnetic powder getting stuck in the end face.

[0057] The above-described embodiments are merely examples of one aspect of the present invention, and any modification and application are possible within the scope of the present invention. For example, it can be obtained by forming an insulating coating on the end faces of a conventional conductor having the same coating thickness on the end faces and the same thickness on the side faces. It can also be obtained by forming a coil conductor using a conventional conductor having the same coating thickness on the end faces and the same thickness on the side faces, and forming insulating coatings on the upper and lower faces of the winding portion.

[0058] In the above-described embodiments, unless otherwise specified, the horizontal, vertical, and other directions, various numerical values, shapes, and materials include a range in which the same action and effect as those directions, numerical values, shapes, and materials are achieved (a so-called equivalent range). [Explanation of symbols]

[0059] 1 Inductor 2 Base 4 External electrode 20 Coil conductor 21 Conductor 21A End face 21B Side 22 Winding section 24 Drawer section 25, 25A, 25B coating 30 cores 50 1st magnetic particle 51 Second magnetic particle MJ winding shaft P1 Center of end face P2 Center of side P3 Both ends of the end face

Claims

1. An inductor having a winding section formed by winding a rectangular conducting wire, a coil conductor having an extraction section drawn out from the winding section, an element body containing magnetic powder and resin and incorporating the coil conductor, and an external electrode formed on a surface of the element body and connected to the coil conductor, the conductor wire includes a conductor, an end face along a direction perpendicular to a winding axis of the coil conductor, and a side face along the direction of the winding axis, and has a coating formed so as to surround the end face and the side face in a cross section perpendicular to a longitudinal direction of the conductor wire, the coating has an insulating layer made of any one of polyurethane resin, polyester resin, epoxy resin, and polyamide-imide resin and in contact with the conductor, and a fusion layer made of polyamide resin and in contact with the insulating layer; the thickness of the coating at the center of the end face of the conductor on the upper and lower surfaces of the winding portion is greater than 100% and not greater than 150% of the thickness of the coating at the side faces, and the thickness of the coating at both end edge portions of the end face is greater than 70% and not greater than 130% of the thickness of the coating at the side faces, The thickness of the central portion of the end face of the conductor wire on the upper and lower surfaces of the winding portion is greater than the thickness of both ends of the end face. Inductor.

2. The inductor of claim 1 , wherein the conductor wire is deformed into an arch shape.

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