Inductors

Abstract

To provide an inductor capable of preventing an electrode material of an external electrode from entering an element body.SOLUTION: An element body of an inductor comprises a magnetic body part 65 at a portion where a lead-out part 24 of a coil conductor is led out. The magnetic body part 65 covers a root part 24A of the lead-out part 24, covers at least one of edge parts 24C located at both sides in a line width direction of the lead-out part 24, and extends in a length direction of the lead-out part 24.SELECTED DRAWING: Figure 9

Description

[Technical field]

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

[0002] Patent Document 1 discloses an inductor having a base body containing magnetic powder and resin and incorporating a coil conductor, an extension portion of the coil conductor extended to a surface portion of the base body, and an external electrode connected to the extension portion. [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] In Patent Document 1, if a gap occurs at the base of the lead-out portion that is led out from the element body, the electrode material of the external electrode will penetrate into the element body through the gap. In recent years, inductors have become smaller and the distance between the windings of the coil conductor inside the element body and the external electrodes has become shorter. If the electrode material of the external electrodes intrudes into the element body, this electrode material may cause abnormal characteristics.

[0005] SUMMARY OF THE PRESENT DISCLOSURE An object of the present invention is to provide an inductor that can prevent the electrode material of the external electrodes from penetrating into the element body. [Means for solving the problem]

[0006] One aspect of the present invention is a magnetic material comprising a magnetic powder and a resin, The coil has a winding section formed by winding a rectangular conductor wire, and an extraction section drawn out from the winding section. A coil conductor is embedded in an element body, and the coil conductor is extended to a surface portion of the element body. The above An inductor having a lead portion and an external electrode connected to the lead portion, the lead-out portion has a base portion that is led out from the winding portion and located in the vicinity of a surface of the element body, and a connection portion that is connected to an external electrode, The element body is a portion from which the drawer portion is drawn. In the embodiment, a boundary region between the connection portion and the base portion of the lead-out portion is The base part In the longitudinal direction of the base portion a magnetic material portion covering at least one of the edge portions located on both sides in the line width direction of the lead-out portion and extending in the length direction of the lead-out portion; the magnetic material portion has a U-shaped or V-shaped recess along the length direction of the pull-out portion, is located between both edge portions of the pull-out portion, the external electrode is connected to the connection portion of the pull-out portion exposed from the magnetic material portion, the magnetic material portion covers the base portion in the length direction of the base portion and at least one of the edge portions located on both sides in the line width direction of the pull-out portion, and extends in the length direction of the pull-out portion and is sandwiched between the external electrode and the pull-out portion. It is an inductor. Effect of the Invention

[0007] According to the present invention, it is possible to prevent the electrode material of the external electrodes from penetrating into the element body. [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. 2 is a perspective view of a first tablet (E-type preform). [Figure 6] FIG. 2 is an explanatory diagram of the thermoforming and curing process. [Figure 7] 1A and 1B are diagrams showing a core containing a coil conductor. [Figure 8] 1A to 1C are diagrams showing a state in which the base portion of the drawn-out portion is properly embedded in the metal magnetic powder. [Figure 9] 1A to 1C are diagrams illustrating the mechanism by which the base portion of the drawn-out portion is embedded in the metal magnetic powder. 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 an inductor 1 according to the present embodiment as viewed from a top surface 12 side, and FIG. 2 is a perspective view of the inductor as viewed from a bottom surface 10 side. The inductor of this embodiment is configured as a surface-mount 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 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 powder 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 first magnetic particles preferably have an average particle size of 19 μm or more and 30 μm or less, and the second magnetic particles preferably have an average particle size of 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 of three or more different particle sizes, including 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 nm to several tens of nm, 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-C-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, 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 in which a conductor wire having a rectangular cross section is wound, and a pair of lead-out portions 24 drawn out from the winding portion 22. The winding portion 22 is formed by spirally winding a conductor wire such that both ends of the conductor wire are located on the outer periphery of the winding portion 22 and are connected to each other on 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 the pair of end faces 14 of the core 30 so that the wide faces of the conductor wire are exposed on the surfaces of the end faces 14 of the core 30, and are electrically connected to the external electrodes 4. Although not shown, the conductor is covered with a coating. The coating includes an insulating layer and a fusion layer on the outside of the insulating layer. The insulating layer insulates the conductor, and the fusion layer bonds adjacent conductors together. The thickness of the insulating layer is 3 μm or more and 9 μm or less, and preferably 4 μm or more and 7 μm or less. Examples of the insulating layer include polyurethane resin, polyester resin, epoxy resin, and polyamideimide resin, and preferably polyamideimide resin. The thickness of the fusion layer is preferably 1 μm or more and 3.5 μm or less. Examples of the fusion layer include polyamide resin. In addition, the coating of the conductor is removed in a region of the lead-out portion 24 of the coil conductor 20 that is to be connected to the external electrode 4 in order to connect to the external electrode 4.

[0019] The external electrode 4 is a so-called five-sided electrode that is provided from an end face 14 of the element body 2 to 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 wiring on a circuit board by an appropriate mounting means such as solder.

[0020] Inductor 1 having such a configuration can improve the DC superposition characteristics by using soft magnetic powder for the magnetic powder, and is therefore used as an electronic component in an electric circuit through which a large current flows, a choke coil in a DC-DC converter circuit or a power supply circuit, and is also used as an electronic component 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 the inductor are not limited to this, and it can also be used, for example, in tuning circuits, filter circuits, rectifying and smoothing circuits, etc.

[0021] In the inductor 1, 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 of 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." 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 forming 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] FIG. 5 is a perspective view of the first tablet of the E type. The first tablet 50 has a recess 51 for receiving the winding portion 22 of the coil conductor 20, and a pair of grooves 52 into which the lead-out portions 24 are led out.

[0026] FIG. 6 is an explanatory diagram of the thermoforming and curing process. In the thermoforming and curing step of FIG. 4, a molding die 55 is prepared. 5 are set in a molding die 55, an upper die 56 is set, and while applying heat, the upper die 56 is moved to apply pressure in the overlapping direction of the first tablet 50 and the second tablet 53, and harden them, thereby integrating the first tablet 50, the coil conductor 20, and the second tablet 53. In this way, the element body 2 in which the coil conductor 20 is enclosed in the core 30 is molded.

[0027] 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.

[0028] 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.

[0029] 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 layer 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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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. Although the plating layer is composed of two layers in this embodiment, it is not limited to this and may be composed of any number of layers.

[0034] 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 electrode 4 may be formed by sputtering or using a copper plate, etc. The external electrode 4 is not limited to a five-sided electrode, and may be a so-called L-shaped electrode in which a metal layer is formed by plating only on both the end surface 14 and the bottom surface 10, or a so-called bottom electrode in which a metal layer is formed only on the bottom surface 10.

[0035] (Embodiment 1) Figure 7A is a diagram showing an element body 2 in which a coil conductor 20 is enclosed in a core 30, and Figure 7B is an enlarged diagram showing the vicinity of a portion of one of the lead portions 24 of the coil conductor 20 in Figure 7A (the lead portion 24 located on the right side in Figure 7A) that is exposed on the surface of the element body 2, and the vicinity of a portion of one of the lead portions 24 of the element body 2 (the lead portion 24 located on the right side in Figure 7A) that is exposed, to show a schematic diagram of the relationship therebetween. The coil conductor 20 includes a winding portion 22 and a pair of lead portions 24. The lead portions 24 are drawn out from the winding portion 22 and include a root portion 24A that is connected to the winding portion 22 at its tip, and a connection portion 24B that is connected to the root portion 24A and connected to the external electrode 4. As shown in FIG. 7B, the root portion 24A has a bent portion R that is bent at a radius CF, and the starting end side of the bent portion R is connected to the winding portion, and the end of the bent portion R is almost flat and connected to the connection portion 24B. The connection portion 24B is exposed on the surface of the element body 2 and is connected to the external electrode 4 formed on the element body 2 as shown in FIG. 3.

[0036] In this embodiment, the magnetic powder of the core 30 includes first magnetic particles 60 having a large average particle size and second magnetic particles 61 having a small average particle size, as shown diagrammatically in FIG. 7B, and each particle 60, 61 is embedded almost uniformly outside the base portion 24A so as to bury the end of the bending portion R, which is bent at a radius CF. As shown in Figure 5, the first tablet 50 has a groove portion 52 from which the pull-out portion 24 is pulled out. By causing the magnetic powder and resin constituting the first tablet 50 and the second tablet 53 to flow during the thermoforming and curing process, the first magnetic particles 60 and the second magnetic particles 61 are almost uniformly filled between the outside of the base portion 24A and the surface of the base body 2 without creating any gaps near the base portion 24A of the pull-out portion 24.

[0037] Figures 8A, 8B, and 8C are schematic views of a state in which base portion 24A of lead portion 24 is properly embedded in metal magnetic powder, and are partial see-through views of the right end face of element body 2 in Figure 7A from the right. In Figures 8A, 8B, and 8C, the top surface of the element body is located at the top, and the bottom surface of the element body is located at the bottom.

[0038] 8A, the magnetic body 2 includes a magnetic material portion 65 extending in the longitudinal direction of the lead-out portion 24, covering both edge portions 24C of the lead-out portion 24 located along the longitudinal direction of the lead-out portion 24 on both sides of the connection portion 24B of the lead-out portion 24 in the width direction of the lead-out portion 24 defined by the line width of the conductor, covering the root portion 24A of the lead-out portion 24 so that the end RF of the bent portion R is embedded in the element body 2 at the portion where the lead-out portion 24 is led out, and the connection portion 24B of the lead-out portion 24 is exposed at the end face of the element body 2. When the lead-out portion 24 is properly embedded in the metal magnetic powder, the magnetic material portion 65 is formed on the edge portion 24C of the lead-out portion 24 so that the distance from the edge of the lead-out portion 24 increases from the tip of the lead-out portion 24 toward the root portion 24A along the longitudinal direction of the conductor, and further formed so that the distance from the edge of the lead-out portion 24 rapidly increases as the lead-out portion 24 approaches the root portion 24A. When the magnetic material part 65 is viewed from the end face side of the element body, the edge of the magnetic material part 65 is inclined in the longitudinal direction of the conductor and is formed into a V-shape that is recessed along the longitudinal direction of the conductor near the base part 24A. Furthermore, the external electrode 4 is formed on the end face of the element body 2, and the magnetic material part 65 is covered by the external electrode 4 by being connected to the lead-out part 24, and is sandwiched between the external electrode 4 and the lead-out part 24. The external electrode 4 is located between the edges on both sides of the lead-out part, and is connected to the connection part 24B of the lead-out part exposed from the magnetic part.

[0039] The positional relationship and shape of the magnetic material portion 65 in relation to the pull-out portion 24 can be confirmed by an X-ray radiograph taken from the end face side of the element body 2. The element body 2 is cut in the DL direction parallel to the main surface of the element body 2 at a position corresponding to the widthwise center of the pull-out portion 24 of the end face of the element body 2 in the X-ray radiograph, and the presence of magnetic powder and resin that constitute the core 30 located on the root portion 24A of the pull-out portion 24 on the cut surface of the element body 2 makes it possible to confirm that the terminal RF of the bent portion R of the root portion 24A of the pull-out portion 24 is at least buried within the element body 2. In addition, it can be determined that the terminal RF of the bent portion R of the root portion 24A of the pull-out portion 24 is buried within the body 2 by checking that a magnetic material portion 65 having a thickness of 30 μm or more is present on the root portion 24A of the pull-out portion 24, closer to the tip of the pull-out portion 24 than the terminal RF of the bent portion R of the root portion 24A of the pull-out portion 24.

[0040] In this way, in the base body 2, at the portion where the pull-out portion 24 is pulled out, a magnetic material portion 65 is provided that covers the root portion 24A of the pull-out portion 24 so that the termination RF of the bend portion R is buried within the base body 2, and that covers both edge portions 24C of the pull-out portion 24 located along the length of the pull-out portion 24 on both sides of the connection portion 24B of the pull-out portion 24 in the width direction of the pull-out portion 24 defined by the line width of the conductor, thereby preventing a gap from occurring between the root of the pull-out portion 24 and the base body 2 as in the conventional case. Furthermore, by slanting the edge of the magnetic material portion 65 when viewed from the end face side of the base body 2 in the longitudinal direction of the conductor and forming a V-shape that is recessed along the longitudinal direction of the conductor near the root portion 24A, the surface of the lead-out portion 24 is exposed in the recess 24D. This increases the exposed area of ​​the lead-out portion 24 without creating a gap between the base of the lead-out portion and the base body 2 as in the conventional case, thereby improving the connection between the lead-out portion 24 and the external electrode 4 and improving the adhesion strength of the external electrode 4 to the base body 2 due to the external electrode material that has entered this V-shaped recess 24D.

[0041] In the element body 2 shown in Figure 8B, when the magnetic material portion 65 is viewed from the end face side of the element body 2, the edge of the magnetic material portion 65 is inclined in the longitudinal direction of the conductor and is formed with a U-shaped recess 24D that is recessed along the longitudinal direction of the conductor near the base portion 24A. In the case of the base body 2 shown in Figure 8B, the above-mentioned method can be used to confirm the positional relationship and shape between the magnetic material portion 65 and the pull-out portion 24, and to confirm that the terminal RF of the bent portion R of the base portion 24A of the pull-out portion 24 is at least buried within the base body 2. In this way, the edge of the magnetic material portion 65 when viewed from the end face side of the base body 2 is inclined in the longitudinal direction of the conductor and formed into a U-shape recessed along the longitudinal direction of the conductor near the base portion 24A, so that the U-shaped recess 24D can increase the exposed area of ​​the pull-out portion 24 more than a V-shaped recess 24D.

[0042] In the base body 2 shown in Figure 8C, a magnetic material portion 65 is formed extending in the longitudinal direction of the lead-out portion 24, covering one of the edges 24C (the edge on the upper surface side of the base body 2) of the lead-out portion 24 located along the longitudinal direction of the lead-out portion 24, on both sides of the connection portion 24B of the lead-out portion 24 in the width direction of the lead-out portion 24 defined by the line width of the conductor wire. The other edge 24C of the lead-out portion 24 (the edge on the bottom surface side of the element body 2) is not covered with the magnetic material part 65 and constitutes a connection part 24B of the lead-out portion 24. In the case of the base body 2 shown in Figure 8C, the above-mentioned method can be used to confirm the positional relationship and shape between the magnetic material portion 65 and the pull-out portion 24, and to confirm that the terminal RF of the bent portion R of the base portion 24A of the pull-out portion 24 is at least buried within the base body 2. In this way, even if one of the edges 24C of the draw-out portion 24 is covered, it is possible to prevent a gap from occurring between the base of the draw-out portion 24 and the base body 2 as in the conventional case, and this one edge may be the edge on the bottom side of the base body 2.

[0043] Figures 9A to 9C are diagrams illustrating the mechanism by which base portion 24A of lead portion 24 is embedded in metal magnetic powder, and are views of a molded body being molded in the mold of Figure 6, viewed from the right side of Figure 6. In Figures 9A to 9C, the top surface of element body 2 to be formed later is located in the upward direction, and the bottom surface of element body 2 to be formed later is located in the downward direction. Arrow P shown in Figure 9A indicates the direction of molding pressure for element body 2. When the amount of resin (weight of resin) is large, the flow rate of the metal magnetic powder increases, so that during molding, from the state shown in Figure 9A, the metal magnetic powder invades the pull-out portion 24 from the base portion 24A side of the pull-out portion 24, as shown in Figure 9B, and flows so as to fill the terminal RF of the bend R of the base portion 24A. As the metal magnetic powder continues to flow, as shown in FIG. 9C, it completely fills base portion 24A of pull-out portion 24 with metal magnetic powder, and the metal magnetic powder also penetrates onto edge portion 24C of pull-out portion 24, covering edge portion 24C of pull-out portion 24. In this way, the base body 2 is provided with a magnetic material portion 65 extending in the longitudinal direction of the pull-out portion 24 at the portion of the end surface where the pull-out portion 24 is pulled out, covering the base portion 24A of the pull-out portion 24 and covering both edge portions 24C of the pull-out portion 24 located on either side of the connection portion 24B of the pull-out portion 24 in the width direction of the pull-out portion 24 defined by the line width of the conductor wire.

[0044] When the amount of resin (weight of resin) is small, the flow rate of the metal magnetic powder decreases when molding pressure is applied, so that the amount of metal magnetic powder penetrating onto the pull-out portion 24 from the base portion 24A side of the pull-out portion 24 decreases, and the amount embedded in the metal magnetic powder of the base portion 24A decreases.

[0045] When the amount of metal magnetic powder embedded in the root portion 24A becomes small, the terminal RF of the bent portion R of the root portion 24A cannot be completely filled, and a gap occurs between the root portion 24A and the element body 2, through which the electrode material of the external electrode 4 penetrates into the element body 2. In recent years, inductors have become smaller, and the distance between the winding portion 22 of the coil conductor 20 inside the element body 2 and the external electrode 4 has become closer. Therefore, if the electrode material of the external electrode 4 penetrates into the element body 2, there is a risk that this electrode material will cause abnormal characteristics. On the other hand, if the amount of magnetic material portion 65 extending in the longitudinal direction of pull-out portion 24 becomes too large, the exposed area of ​​pull-out portion 24 will be reduced, and there is a risk that an exposed area suitable for connecting external electrode 4 cannot be secured. Therefore, by appropriately adjusting the amount of resin (weight of resin), it is possible to prevent gaps from occurring at the base of the lead-out portion 24 extended from the element body 2, and to make the exposed area of ​​the lead-out portion 24 suitable for connecting the external electrode 4.

[0046] An experiment was conducted in which a coil conductor 20 made of wound wire was enclosed in a core 30 using a mixed powder of metal magnetic powder and resin, and the element 2 was formed so that the winding axis of the coil conductor 20 was perpendicular to the mounting surface of the element 2. In this experimental example, the element body 2 had a length L dimension of 3.5 mm, a width W dimension of 2.5 mm, and a thickness T dimension of 1.9 mm, and the coil conductor 20 had an inner circumference in the longitudinal direction of 1.71 mm, an outer circumference in the longitudinal direction of 2.78 mm, an inner circumference in the lateral direction of 0.92 mm, an outer circumference in the lateral direction of 1.99 mm, and a height of 1.35 mm. The metallic magnetic powder used had large first magnetic particles 60 with an average particle size of 24.4 μm and small second magnetic particles 61 with an average particle size of 4.0 μm. Furthermore, the ratio of (weight of resin) / (total weight of metal magnetic powder and resin) was set to 2.9 wt% or more and 3.1 wt% or less. The ratio of (weight of resin) / (total weight of metal magnetic powder and resin) can be measured by measuring the weight of each of them before mixing them together. When measuring the weight of core 30 as a molded body obtained by mixing and compression molding them, the weight of metal magnetic powder and resin can be measured by cutting element 2 in the longitudinal direction through the winding axis of coil conductor 20 as seen from the top surface of the element, sampling metal magnetic powder and resin along the winding axis of coil conductor 20 over a 0.5 mm square area and 0.5 mm deep centered at a position 0.5 mm from the main surface of the element, measuring the weight of the sample, and then burning the sample at a temperature at which the resin burns in a non-oxidizing atmosphere, measuring the weight of the residue, and calculating the ratio. The molding pressure for the element 2 is 50 MPa (approximately 500 kgf / cm2).

[0047] (Evaluation Results of the First Embodiment) As a result of the experiments, it was found that appropriate fluidity of the metal magnetic powder could be obtained in all cases where the (weight of resin) / (total weight of metal magnetic powder and resin) was in the range of 2.9 wt% or more and 3.1 wt% or less, and the filling rate of the magnetic powder in the magnetic material part was increased, preventing deterioration of the magnetic permeability of the core.

[0048] (Embodiment 2) In this embodiment, by adjusting the radius CF shown in Figures 7A and 7B, the magnetic powder of the core 30 contains first magnetic particles 60 having a large average particle size and second magnetic particles 61 having a small average particle size, as shown diagrammatically in Figure 7B, and each particle 60, 61 is buried almost uniformly outside the base portion 24A so that the terminal RF of the bending portion R, which bends at the radius CF, is buried.

[0049] An experiment was conducted in which a coil conductor 20 made of wound wire was enclosed in a core 30 using a mixed powder of metal magnetic powder and resin, and the element 2 was formed so that the winding axis of the coil conductor 20 was perpendicular to the mounting surface of the element 2.

[0050] In this experimental example, the element body 2 had a length L dimension of 3.5 mm, a width W dimension of 2.5 mm, and a thickness T dimension of 1.9 mm, and the coil conductor 20 had an inner circumference in the longitudinal direction of 1.71 mm, an outer circumference in the longitudinal direction of 2.78 mm, an inner circumference in the lateral direction of 0.92 mm, an outer circumference in the lateral direction of 1.99 mm, a height of 1.35 mm, and a radius CF of 251 μm or more and 388 μm or less. The radius CF can be calculated by taking an X-ray from the top surface of the element body 2, drawing a circle as shown by the dotted line in FIG. 7A along the inner circular arc close to the winding portion 22 formed by the starting end and ending end RF of the bend R, and determining the radius of the circle. The metallic magnetic powder used had large first magnetic particles 60 with an average particle size of 24.4 μm and small second magnetic particles 61 with an average particle size of 4.0 μm. Furthermore, (weight of resin) / (total weight of metal magnetic powder and resin) was set to 3.0 wt %, and the molding pressure for element body 2 was set to 50 MPa (approximately 500 kgf / cm 2 ).

[0051] (Evaluation Results of the Second Embodiment) As a result of the experiments, it was found that when the radius CF was in the range of 251 μm or more and 388 μm or less, an appropriate flow rate of the metal magnetic powder could be obtained, the filling rate of the magnetic powder in the magnetic material portion 65 could be increased, and deterioration of the magnetic permeability of the core 30 could be prevented.

[0052] The above-described embodiments are merely examples of the present invention, and any modifications and applications are possible without departing from the spirit and scope of the present invention.

[0053] 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]

[0054] 1 Inductor 2 Base 4 External electrode 20 Coil conductor 21 Conductor 21A End face 21B Side 22 Winding section 24 Drawer section 24A Base 24B Connection 24C Dent 30 cores 60 1st magnetic particle 61 Second magnetic particle 65 Magnetic material part

Claims

1. An inductor comprising: a winding section formed by winding a rectangular conductor wire containing magnetic powder and resin; an element body incorporating a coil conductor having an extension section extended from the winding section; the extension section of the coil conductor extended to a surface portion of the element body; and an external electrode connected to the extension section, the lead-out portion has a base portion that is led out from the winding portion and located in the vicinity of a surface of the element body, and a connection portion that is connected to an external electrode, the element body includes a magnetic material portion that covers the base portion in a longitudinal direction of the base portion at a boundary region between the connection portion and the base portion of the lead portion at a portion where the lead portion is led out, and that covers at least one of edge portions located on both sides in a line width direction of the lead portion and extends in a longitudinal direction of the lead portion, The magnetic body portion has a U-shaped or V-shaped recess extending along the length of the pull-out portion, the external electrode is connected to a connection portion of the lead portion that is located between both edge portions of the lead portion and is exposed from the magnetic material portion; the magnetic material portion covers the base portion in a length direction thereof and covers at least one of the edge portions located on both sides of the lead portion in a line width direction thereof, and extends in the length direction of the lead portion, and is sandwiched between the external electrode and the lead portion. Inductor.

2. 2. The inductor according to claim 1, wherein the element body has a ratio of (weight of resin) / (total weight of metal magnetic powder and resin) set to 2.9 wt % or more and 3.1 wt % or less.

3. The inductor according to claim 1 , wherein a base portion of the lead-out portion is bent at a radius CF, and the radius CF is set to be equal to or greater than 251 μm and equal to or less than 388 μm.

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