Inductor and method for manufacturing inductor

Abstract

The present invention increases the fixing strength between a lead-out portion and an external electrode and reduces DC resistance by preventing an insulation coating of a lead-out portion conductive wire from being exposed on the surface of an element body.　This inductor comprises: a coil conductor having a pair of lead-out portions each composed of a conductive wire comprising a conductor and an insulation film coating the periphery of the conductor; an element body containing magnetic particles and resin and enclosing the coil conductor; and an external electrode connected to an exposed part of each lead-out portion exposed from the surface of the element body. In the exposed part of at least one of the lead-out portions, the conductor of the conductive wire is exposed from an opening in the insulation film and extends on the surface of the element body. The area of the exposed surface of the conductor extending on the surface of the element body is greater than the area of the opening in the insulation film.

Description

Inductor and method for manufacturing the same

[0001] The present invention relates to an inductor and a method for manufacturing an inductor.

[0002] Patent Document 1 describes an inductor having a coil conductor, an element body containing metal magnetic particles and resin and enclosing the coil conductor, and a pair of external electrodes electrically connected to the ends of the coil conductor. In this inductor, the surface of the lead-out portion of the coil conductor is exposed on the surface of the element body, and a plating layer is formed on the portion of the element body surface where the external electrodes will be formed after the resin contained in the element body is removed. This electrically connects the metal magnetic particles contained in the element body, the lead-out portion, and the external electrodes including the plating layer.

[0003] JP 2016-58418 A

[0004] In the above-described conventional inductor, for example, when the coil conductor is formed of a lead wire having a conductor and an insulating coating, after forming an element body so that the lead portions of the coil conductor are exposed, by irradiating the external electrode formation area on the element body surface, including the exposed lead portions, with laser light, the resin on the element body surface is removed and the insulating coating of the lead portions exposed on the element body surface is also removed. During this process, there may be portions of the insulating coating of the lead wire that are not sufficiently removed near the contour of the lead portion exposed on the element body surface (i.e., the boundary between the exposed surface of the lead portion and the surrounding element body surface). Such remaining insulating coating not only reduces the connection area between the conductor of the lead portion and the external electrode, but also serves as a barrier for the plating metal when the external electrode is formed by metal plating in a subsequent process, thereby adversely affecting the bond strength and DC resistance between the lead portion and the external electrode.

[0005] The object of the present invention is to prevent an external electrode from being formed on the insulating coating of the lead portion exposed on the surface of the element body in an inductor that includes a coil conductor having a pair of lead portions made of a conducting wire having a conductor and an insulating coating, thereby improving the bonding strength between the lead portion and the external electrode and reducing the DC resistance, in an element body that includes magnetic particles and resin.

[0006] One aspect of the present invention is an inductor comprising: a coil conductor having a pair of lead-out portions consisting of a conducting wire having a conductor and an insulating coating covering the conductor; a base body containing magnetic particles and resin and containing the coil conductor; and an external electrode connected to an exposed portion of the lead-out portion that is exposed from the surface of the base body, wherein at least one of the pair of lead-out portions has, at the exposed portion, the conductor of the conducting wire exposed from an opening in the insulating coating and extending onto the surface of the base body, and the area of ​​the exposed surface of the conductor extending onto the surface of the base body is larger than the area of ​​the opening in the insulating coating. Another aspect of the present invention is a method for manufacturing an inductor, the method comprising the steps of: embedding a coil conductor having a pair of lead portions in an element body containing magnetic particles and a resin so that the lead portions are exposed from the surface of the element body; grinding or polishing the surface of the element body where the lead portions are exposed, thereby removing an insulating coating of the conductor wire of the coil conductor along the surface of the element body to form an opening in the insulating coating and spreading the conductor of the conductor wire exposed from the opening in the insulating coating on the surface of the element body to form an exposed surface of the conductor; and forming an external electrode on the surface of the element body including the exposed surface. This specification is intended to include the entire content of Japanese Patent Application No. 2024-027622, ​​filed on February 27, 2024.

[0007] According to the present invention, in an inductor that includes a coil conductor having a pair of lead portions made of a conducting wire having a conductor and an insulating coating, and that is enclosed in a body containing magnetic particles and resin, it is possible to prevent an external electrode from being formed on the insulating coating of the lead portion exposed on the surface of the body, thereby improving the bonding strength between the lead portion and the external electrode and reducing the DC resistance.

[0008] FIG. 1 is a perspective view of an inductor according to an embodiment of the present invention, viewed from the top side. FIG. 2 is a perspective view of the inductor, viewed from the bottom side. FIG. 3 is a see-through perspective view showing the internal configuration of the inductor. FIG. 4 is a plan view see-through view of the inductor shown in FIG. 3, viewed from the top side. FIG. 5 is a view of the end face of the inductor shown in FIG. 4. FIG. 6 is a cross-sectional view of the inductor shown in FIG. 5, taken along line VI-VI. FIG. 7 is a micrograph of the end face of an element body during manufacturing of an inductor. FIG. 8 shows an example of a configuration in which the lead portion is inclined toward the interior of the element body with respect to the end face of the element body during manufacturing of an inductor. FIG. 9 is an enlarged cross-sectional photograph showing the boundary between the lead portion and the external electrode. FIG. 10 is a diagram showing the manufacturing process of an inductor.

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. [1. Inductor Configuration] First, the configuration of an inductor 1 according to this embodiment will be described. [1.1 Overall Configuration of Inductor] Fig. 1 is a perspective view of the inductor 1 according to this embodiment as viewed from the top surface 12 side, and Fig. 2 is a perspective view of the inductor 1 as viewed from the bottom surface 10 side. The inductor 1 of this embodiment is configured as a surface-mounted electronic component, and includes an element body 2 having a substantially rectangular parallelepiped shape, which is one form 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 substrate (not shown) during mounting is defined as the bottom surface 10, the second main surface opposite the bottom surface 10 is defined as the top surface 12, a pair of third main surfaces perpendicular to the bottom surface 10 are defined 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 defined as side surfaces 16. As shown in FIG. 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 the pair of side surfaces 16 is defined as the width W of the element body 2, and the distance between the pair of end surfaces 14 is defined as the length L of the element body 2. Furthermore, 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 dimensions of the inductor 1 are, for example, a length L of 1.4 mm, a width W of 1.2 mm, and a thickness T of 0.65 mm.

[0011] 3 is a see-through perspective view showing the internal configuration of the inductor 1. 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 molded inductor in which the coil conductor 20 is sealed in the core 30.

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

[0013] The magnetic particles of this embodiment contain particles of two particle sizes: first magnetic particles with a relatively large average particle size and second magnetic particles with a relatively small average particle size. This allows the second magnetic particles, which are small particles, to penetrate between the first magnetic particles with the resin during compression molding, thereby increasing the magnetic particle filling rate in the core 30 and improving magnetic permeability. The average particle size (D50) of the first magnetic particles is preferably 20 μm or more and 68 μm or less, and more preferably 21.4 μm or more and 27.4 μm or less. The average particle size (D50) of the second magnetic particles is preferably 1 μm or more and 6 μm or less, and more preferably 1.5 μm or more and 1.8 μm or less. The magnetic particles may contain particles with different average particle sizes from the first magnetic particles and the second magnetic particles, thereby containing particles of three or more particle sizes.

[0014] The first magnetic particles and the second magnetic particles are both particles having metal particles and an insulating film covering the surfaces of the metal particles with a thickness of several nanometers to several tens of nanometers. Covering the metal particles with an insulating film increases the insulation resistance and withstand voltage. In the first magnetic particles of this embodiment, Fe—Si—B amorphous alloy powder is used for the metal particles, and zinc phosphate glass with a thickness of 10 nm to 50 nm is used for the insulating film. Furthermore, in the second magnetic particles of this embodiment, carbonyl iron powder is used for the metal particles, and a silica film with a thickness of 5 nm to 15 nm is used for the insulating film.

[0015] In the mixed powder of this embodiment, the resin material is an epoxy resin whose main component is a phenol alkyl epoxy resin. The amount of second magnetic particles contained in the mixed powder is, for example, 15 wt% to 30 wt% and preferably 20 wt% to 30 wt% based on the total weight of the magnetic particles. The resin content in the mixed powder is 2.0 wt% to 3.5 wt% based on the total weight of the mixed powder.

[0016] As shown in FIG. 3 , the coil conductor 20 includes a winding portion 22 around which a conductor wire is wound and a pair of lead portions 24 drawn from the winding portion 22. The coil conductor 20 does not necessarily have to be wound, but may be linear, meander-shaped, or the like. In these cases, the coil conductor 20 includes the linear or meander-shaped conductor portion instead of the winding portion 22, and a pair of lead portions 24 extending from the conductor portion. The conductor forming the coil conductor 20 includes a copper conductor and an insulating coating formed on the surface of the conductor. The conductor is a strip-shaped conductor (so-called flat conductor). The thickness of the conductor is 118 μm or less, preferably 52 μm or more. The width of the conductor is 200 μm or less, preferably 110 μm or more. The aspect ratio of the conductor is, for example, 1.2 to 3.4. The insulating coating is made of, for example, polyurethane resin, polyester resin, epoxy resin, or polyimide amide resin, and is preferably polyimide amide resin. The insulating coating has a thickness of, for example, 3 μm.

[0017] The conductor wire may have a bonding layer on the insulating coating for bonding overlapping conductor wires together in the winding portion 22. For example, the bonding layer is made of polyamide resin, and the thickness thereof is preferably 1 μm or more and 25 μm or less, more preferably 2 μm or more and 25 μm or less, and even more preferably 2 μm or more and 4 μm or less.

[0018] The winding portion 22 of the coil conductor 20 is formed by winding a strip-shaped conductor wire (hereinafter simply referred to as a conductor wire) in a spiral shape, with both ends drawn out to the outer periphery 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 central axis of the winding portion 22 oriented along the thickness direction DT of the element body 2. The drawn-out portions 24 extend from the winding portion 22 to each of the pair of end faces 14, with one main surface exposed from the element body 2 and the other main surface embedded in the element body 2.

[0019] An external electrode 4 is electrically connected to the exposed portion of the lead portion 24 that is exposed from the surface of the element body 2 .

[0020] The pair of external electrodes 4 are so-called L-shaped electrodes, consisting of L-shaped members extending from each of the end faces 14 of the element body 2 to the bottom face 10. Each of the external electrodes 4 is connected to the lead-out portion 24 of the coil conductor 20 at the end face 14, and the portion 4A (FIG. 2) extending to the bottom face 10 is electrically connected to wiring on the circuit board by an appropriate mounting means such as solder.

[0021] An element body protective layer (not shown in FIGS. 1 to 5 ) is formed on the surface of the element body 2 excluding the area of ​​the external electrodes 4. The element body protective layer is made of, for example, phenoxy resin and novolac resin, and contains nanosilica as a filler. The element body protective layer is formed on the surface of the element body 2 to a thickness of 10 μm to 30 μm.

[0022] The inductor 1 having such a configuration can improve the DC bias characteristics by using a soft magnetic material for the magnetic particles, and is therefore used as an electronic component in electric circuits through which large currents flow, a choke coil in DC-DC converter circuits and power supply circuits, and 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 1 are not limited to this, and it can also be used, for example, in tuning circuits, filter circuits, rectifying and smoothing circuits, etc.

[0023] [1.2 Configuration of the Boundary Between the Lead Portion and the External Electrode] As described above in connection with the background art, in conventional inductors, the insulating coating of the lead portion's conductor wire remaining near the contour of the lead portion exposed on the surface of the element body (i.e., the boundary between the exposed surface of the lead portion and the surrounding surface of the element body) reduces the connection area between the lead portion's conductor and the external electrode, and also forms an area where the plated metal does not adhere when the external electrode is formed by metal plating in a later process, which can adversely affect the bonding strength between the lead portion and the external electrode and the DC resistance.

[0024] Therefore, in the inductor 1 according to this embodiment, the boundary portion between the lead portion 24 and the external electrode 4 on the surface of the element body 2 is configured as follows.

[0025] Fig. 4 is a planar perspective view of the inductor 1 shown in Fig. 1 and Fig. 3, viewed from the top surface 12. Fig. 5 is a view of the right end surface 14 of the inductor 1 shown in Fig. 4, viewed from the right side in the direction of block arrow AR (-DL direction). Fig. 6 is a cross-sectional view taken along the arrows VI-VI in Fig. 5, showing the configuration of the boundary portion between the lead portion 24 and the external electrode 4 on the surface of the element body 2.

[0026] 5, the portion indicated by the dotted rectangle indicates the exposed portion Ex of the lead portion 24 that is exposed from the end surface 14 of the element body 2. The dotted rectangle in the figure indicates an opening OP (described later) in the insulating coating 51 of the conductor 50 that forms the lead portion 24.

[0027] 6 , in this embodiment, particularly in the lead-out portion 24, the conductor 52 of the conducting wire 50 is exposed from the opening OP in the insulating coating 51 at the exposed portion Ex that is exposed from the surface of the element body 2, and extends onto the surface of the element body 2 (on the end face 14 of the element body 2 in the illustrated example). The area of ​​the exposed surface of the conductor 52 extending onto the surface of the element body 2 (i.e., the area of ​​the exposed portion Ex) is larger than the area of ​​the opening OP in the insulating coating 51. The area of ​​the opening OP in the insulating coating 51 is preferably, for example, 1.1 times or more and 2 times or less the area of ​​the exposed portion Ex.

[0028] As shown in the manufacturing process described below, the above configuration can be formed, for example, by grinding or polishing the end face 14 on the surface of the element body 2 where the lead portion 24 is exposed, removing the insulating coating 51 of the conductor 50, and spreading the conductor 52 exposed from the insulating coating 51 along the surface of the element body 2. Note that, at the edge of the opening OP in the insulating coating 51 in the exposed portion Ex, burrs BR of the insulating coating 51 may be formed toward the outside of the opening OP, as shown in Fig. 6. If burrs BR are formed in the grinding or polishing process, the conductor 52 can be spread on the surface of the element body 2 to an area that covers the burrs BR.

[0029] With the above configuration, at the exposed portions Ex of the lead portions 24, the conductors 52 of the lead portions 24 cover most or all of the insulating coating 51 present at the edges of the openings in the insulating coating 51, and extend across the surface of the element body 2. Therefore, in the inductor 1 having the above configuration, exposure of the insulating coating 51 at the exposed portions Ex of the lead portions 24 of the coil conductor 20 that are exposed on the surface of the element body 2 is effectively suppressed, thereby improving the bonding strength between the lead portions and the external electrodes and reducing the DC resistance.

[0030] The areas of the exposed portion Ex and the opening OP can be measured as follows. First, an image is taken from the end face 14 side of the element body 2 using a CT (Computed Tomography) device, and the frames of the CT image are advanced from the center of the element body 2 to the first CT image in which the opening OP in the insulating coating 51 can be identified, thereby identifying a measurement image of the area of ​​the opening OP in the insulating coating 51. Then, the frames of the CT image are further advanced to the first CT image in which the exposed surface of the conductor 52 can be identified, thereby identifying a measurement image of the exposed area of ​​the conductor 52. Each measurement image is then loaded into image software (myVGL (manufactured by Volume Graphics)), and the areas are measured in comparison with the scale provided on the CT image, thereby measuring the areas of the opening OP and the exposed surface of the conductor 52.

[0031] 5, in the inductor 1, it is preferable that the opening OP in the insulating coating 51 is covered by the conductor 52 of the lead portion 24 extending onto the surface of the element body 2, so that the insulating coating 51 is not exposed at all on the surface of the element body 2. This configuration can be formed by grinding or polishing the end face 14 of the element body 2 where the lead portion 24 is exposed, by grinding or polishing the element body 2 with a grinding stone in a circular motion.

[0032] As a result, in the inductor 1, exposure of the insulating coating 51 at the exposed portion Ex of the lead-out portion 24 of the coil conductor 20 that is exposed on the surface of the base body 2 is prevented, thereby improving the bonding strength between the lead-out portion 24 and the external electrode 4 and further effectively reducing the DC resistance.

[0033] Furthermore, the boundary line between the surface of the element body 2 and the exposed surface of the conductor 52 extending on the surface of the element body 2 (i.e., the outer boundary line of the exposed portion Ex of the lead portion 24) may include irregularities, thereby ensuring a wider connection area between the conductor 52 of the lead portion 24 and the external electrode 4 and further reducing the DC resistance.

[0034] Furthermore, in the exposed portion Ex, the surface roughness of the exposed surface of the conductor 52 of the lead-out portion 24 is greater (i.e., rougher) than the surface roughness of a portion of the conductor 52 of the lead-out portion 24 from which the insulating coating 51 has not been removed (for example, the portion of the conductor 52 covered with the insulating coating 51 on the left side of the lead-out portion 24 shown in FIG. 6 ). The surface roughness of the exposed surface of the conductor 52 of the lead-out portion 24 can be adjusted, for example, by the roughness of the grinding stone used in grinding or polishing the end face 14 described above.

[0035] This increases the surface roughness of the boundary surface between the conductor 52 of the lead-out portion 24 and the external electrode 4, thereby further improving the connection strength between the conductor 52 and the external electrode 4 due to the anchor effect that can occur at the boundary surface.

[0036] 7 is a micrograph showing an example of the state of the end surface 14 of the element body 2 during the manufacture of the inductor 1. The dotted rectangle in the figure indicates the position of the opening OP in the insulating coating 51 of the lead-out portion 24. In the example shown, the conductor 52 of the lead-out portion 24 extends in all directions from the opening OP along the surface of the element body 2 so as to cover the entire opening OP in the insulating coating 51. In addition, in the example shown, the exposed surface of the conductor 52 is formed in a shape that protrudes downward in the figure from the opening SP along the surface of the element body 2, and the boundary line between the exposed surface of the conductor 52 and the surface of the element body 2 has an unevenness.

[0037] Furthermore, from the micrograph shown in FIG. 7, it can be seen that the exposed surface of the conductor 52 is roughened along with the surface of the surrounding element body 2.

[0038] Figure 9 is a cross-sectional photograph showing the boundary between the lead portion 24 and the external electrode 4 on the surface of the element body 2 of the fabricated inductor 1. The cross-sectional photograph of Figure 9 corresponds to the cross section of the range of part Q shown in Figure 6. In the example of Figure 9, the insulating coating 51 has a burr BR at the lower end shown in the figure. The conductor 52 extends beyond the burr BR of the insulating coating 51 to the lower side in the figure, covering the entire insulating coating 51. The boundary between the lead portion 24 and the external electrode 4 can be more clearly identified by observing the electron channeling contrast using a scanning microscope.

[0039] 10 is a diagram showing the manufacturing process of the inductor 1. As shown in the figure, the manufacturing process of the inductor 1 includes a coil conductor forming step (S1), a preform forming step (S2), an element molding step (S3), a barrel polishing step (S4), an end face polishing step (S5), and an external electrode forming step (S6).

[0040] The coil conductor forming step (S1) is a step of forming the coil conductor 20 from a conductive wire. In this step, 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 using a winding method known as "alpha winding." Alpha winding refers to a state in which the lead-out portions 24 at the start and end of the conductive wire, which functions as a conductor, are wound in two spiral stages so that they are located on the outer periphery. The number of turns of the coil conductor 20 is not particularly limited.

[0041] The preform formation step (S2) is a step of forming a preform called a tablet. The preform is formed by pressing the mixed powder, which is the material of the element 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.

[0042] In the element molding step (S3), 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 to harden them, integrating the first tablet, the coil conductor, and the second tablet. This forms the element 2 in which the coil conductor 20 is enclosed in the core 30. The thermoforming and hardening step corresponds to the element molding step in this disclosure.

[0043] The barrel polishing step (S4) is a step of barrel polishing this molded body, and by this step, the corners of the element body 2 are rounded.

[0044] In the end surface polishing step (S5), as shown in FIG. 8 , the end surfaces of the obtained element body 2 are ground or polished with the lead portions 24 exposed until the element body 2 has a predetermined length. This grinds the element body 2, including the lead portions 24, along the surface of the element body 2. At this time, the insulating coating 51 of the conductor 50 of the lead portion 24 is removed along the surface of the element body 2 to form an opening OP in the insulating coating 51, and the conductor 52 of the conductor 50 exposed through the opening OP in the insulating coating 51 is spread along the surface of the element body 2 to form an exposed surface of the conductor 52. By grinding or polishing the element body 2 in a circular motion against the grindstone, the conductor 52 can be extended in all directions to cover the entire opening OP in the insulating coating 51. The surface roughness of the exposed surface of the conductor 52 can be adjusted by adjusting the roughness of the grindstone used for grinding or polishing.

[0045] The surface roughness of the exposed surface of the conductor 52 and the surface roughness of the portion of the conductor 52 where the insulating coating 51 has not been removed can be determined by loading the electron channeling contrast photograph of the scanning microscope into image software (VHX, manufactured by Keyence Corporation) and using the measurement function of the image software to compare the unevenness of the exposed surface of the conductor 52 and the unevenness of the surface of the portion of the conductor 52 where the insulating coating 51 has not been removed with the scale on the electron channeling contrast photograph of the scanning microscope.

[0046] As shown in Figure 9, if the lead-out portion 24 of the coil conductor 20 embedded in the element body 2 is inclined toward the inside of the element body 2 with respect to the end face 14, the length of the lead-out portion 24 exposed at the end face 14 may be shorter before and after polishing the end face 14.

[0047] The external electrode forming step (S6) is a step of forming the external electrodes 4 on the core 30, and includes an element body protective layer forming step (S61), a surface treatment step (S62), and a plating layer forming step (S63).

[0048] The element body protective layer forming step (S61) is a step of coating the entire surface of this molded body with an insulating resin.

[0049] The surface treatment step (S62) is a step of modifying the surface of the planned electrode area by irradiating the area with laser light. Here, the planned electrode area refers to the area on the surface of the core 30 where the external electrode 4 is to be formed, including the area where the lead-out portion 24 is exposed. Specifically, by irradiating the laser light, the element body protective layer on the surface of the core 30 and the coating layer on the lead-out portion 24 of the coil conductor 20 are removed within the planned electrode area, the resin on the surface of the core 30 is removed, 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 area than in other surface areas of the core 30. After irradiating the laser light, a cleaning process (e.g., etching) may be performed to clean the surface of the planned electrode area.

[0050] In the plating layer forming step (S63), copper is barrel-plated on the surface of the core 30 to form a copper plating layer at the electrode-planed location irradiated with the laser light, thereby forming the external electrode 4. The external electrode 4 may be formed by further providing a Ni plating layer and a Sn plating layer on the copper plating layer.

[0051] In the above-described embodiment, the lead-out portion 24, which is a rectangular conductor wire, has a side surface of the conductor 52 exposed on the surface of the element body 2. However, any portion of the lead-out portion 24 may be exposed on the surface of the element body 2, depending on the design of the inductor 1. For example, the end face of the conductor wire 50 that constitutes the lead-out portion 24 may be exposed from the surface of the element body 2.

[0052] In addition, in this embodiment, the conductor wire 50 constituting the coil conductor 20 is a flat conductor wire having a substantially rectangular cross section, but the conductor wire 50 may have any cross-sectional shape. For example, the conductor wire 50 may have a circular cross section. In the lead-out portion 24, the side or end face of the conductor wire 50 having a circular cross section may be exposed on the surface of the element body 2.

[0053] In the above-described embodiment, the external electrode 4 is formed as an L-shaped electrode. However, the external electrode 4 is not limited to an L-shaped electrode, and may be formed as a so-called five-sided electrode that is provided over the entire end face 14 and over a portion of each of the bottom face 10, top face 12, and pair of side faces 16 adjacent to the end face 14. Note that when the five-sided electrode is applied by immersion in a conductive resin, the element protective layer forming step (S61) is not necessarily required.

[0054] All of the above-described embodiments and modifications are merely examples of one aspect of the present invention, and can be modified and applied as desired without departing from the spirit of the present invention. Furthermore, unless otherwise specified, the horizontal, vertical, and other directions, various numerical values, shapes, and materials in the above-described embodiments include a range that provides the same action and effect as those directions, numerical values, shapes, and materials (so-called equivalent ranges).

[0055] 4. Configurations Supported by the Above-described Embodiments The above-described embodiments support the following configurations.

[0056] (Configuration 1) An inductor comprising: a coil conductor having a pair of lead portions made of a conducting wire having a conductor and an insulating coating covering the periphery of the conductor; an element body containing magnetic particles and resin and encapsulating the coil conductor; and an external electrode connected to an exposed portion of the lead portion that is exposed from a surface of the element body, wherein in at least one of the pair of lead portions, the conductor of the conducting wire is exposed from an opening in the insulating coating and extends onto the surface of the element body, and the area of ​​the exposed surface of the conductor extending onto the surface of the element body is larger than the area of ​​the opening in the insulating coating. According to the inductor of Configuration 1, in the exposed portion of the lead portion, the conductor of the lead portion extends over the surface of the element body, covering most or all of the insulating coating that is present at the edge of the opening in the insulating coating. Therefore, in the inductor of configuration 1, exposure of the insulating coating at the exposed portion of the lead-out portion is effectively suppressed, preventing the formation of an external electrode on the exposed insulating coating, thereby improving the bonding strength between the lead-out portion and the external electrode and reducing the DC resistance.

[0057] (Configuration 2) The inductor according to Configuration 1, wherein the coil conductor has a winding portion around which a conductor wire is wound and the lead-out portion drawn out from the winding portion. According to the inductor of Configuration 2, in an inductor having a winding portion around which a conductor wire is wound, it is possible to improve the bonding strength between the lead-out portion and the external electrode and reduce the DC resistance.

[0058] (Configuration 3) The inductor according to Configuration 1 or 2, wherein the openings in the insulating coating are covered by the conductor extending on the surface of the element body, and the insulating coating is not exposed on the surface of the element body. The inductor of Configuration 3 prevents exposure of the insulating coating at the exposed parts of the lead-out portions, thereby improving the bonding strength between the lead-out portions and the external electrodes and further effectively reducing DC resistance.

[0059] (Configuration 4) The inductor according to any one of Configurations 1 to 3, wherein a boundary line between the surface of the element body and an exposed surface of the conductor extending on the surface of the element body includes irregularities. With the inductor of Configuration 4, a larger connection area between the conductor of the lead-out portion and the external electrode can be ensured, thereby further reducing DC resistance.

[0060] (Configuration 5) The inductor according to any one of Configurations 1 to 4, wherein in the exposed portion of the lead-out portion, the surface roughness of the exposed surface of the conductor is greater than the surface roughness of a portion of the conductor where the insulating coating has not been removed. According to the inductor of Configuration 5, the surface roughness of the boundary surface between the conductor of the lead-out portion and the external electrode can be increased, and the anchor effect that can occur at the boundary surface can further improve the connection strength between the conductor and the external electrode.

[0061] (Configuration 6) A method for manufacturing an inductor, comprising the steps of: embedding a coil conductor having a pair of lead portions in an element body containing magnetic particles and a resin so that the lead portions are exposed from the surface of the element body; grinding or polishing the surface of the element body where the lead portions are exposed, thereby removing an insulating coating of the lead wire of the coil conductor along the surface of the element body to form an opening in the insulating coating and spreading the conductor of the lead wire exposed from the opening in the insulating coating on the surface of the element body to form an exposed surface of the conductor; and forming an external electrode on the surface of the element body including the exposed surface. The manufacturing method of Configuration 6 effectively prevents exposure of the insulating coating at the exposed parts of the lead portions, making it possible to easily manufacture an inductor with improved bonding strength between the lead portions and the external electrode and reduced DC resistance.

[0062] 1...inductor, 2...element body, 4...external electrode, 5...element body protective layer, 10...bottom surface, 12...top surface, 14...end surface, 16...side surface, 20...coil conductor, 22...winding portion, 24...drawing portion, 30...core, 50...conductor, 51...insulating coating, 52...conductor, BR...burr, Ex...exposed portion, OP...opening.

Claims

1. A coil conductor having a pair of lead-out portions, each consisting of a wire having a conductor and an insulating coating covering the conductor's periphery, A base body containing magnetic particles and resin, which encloses the coil conductor, An external electrode connected to the exposed portion of the extraction section that is exposed from the surface of the base body, Equipped with, The pair of extensions, at least one of which has an exposed portion, The conductor of the aforementioned wire is exposed from the opening in the insulating coating and extends onto the surface of the substrate. The area of ​​the exposed surface of the conductor extending on the surface of the substrate is larger than the area of ​​the opening in the insulating coating. Inductor.

2. The coil conductor has a winding portion in which a conductor wire is wound, and an extension portion drawn out from the winding portion. The inductor according to claim 1.

3. The opening in the insulating coating is covered by the conductor extending onto the surface of the substrate, and the insulating coating is not exposed to the surface of the substrate. The inductor according to claim 1.

4. The boundary line between the exposed surface of the conductor extending onto the surface of the substrate and the surface of the substrate includes irregularities. The inductor according to claim 1.

5. In the exposed portion of the aforementioned pull-out section, The surface roughness of the exposed surface of the conductor is greater than the surface roughness of the portion of the conductor where the insulating coating has not been removed. The inductor according to any one of claims 1 to 4.

6. A step of embedding the coil conductor in a substrate such that the lead portions of the coil conductor, which have a pair of lead portions, are exposed from the surface of the substrate containing magnetic particles and resin, The process involves grinding or polishing the surface of the base body in which the lead portion is exposed to remove the insulating coating of the coil conductor wire along the surface of the base body, thereby forming an opening in the insulating coating, and spreading the conductor wire exposed from the opening in the insulating coating on the surface of the base body to form an exposed surface of the conductor, A step of forming an external electrode on the surface of the base body including the exposed surface, Having, A method for manufacturing inductors.

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