Inductor

Abstract

Provided is a highly reliable inductor with fewer manufacturing variations in electrical characteristics obtained by suppressing the occurrence of positional deviation of a coil and damage to a coil conductor during element body forming.　The inductor comprises: a coil including a winding portion around which a conductive wire having a rectangular cross section with an insulating coating is wound, and two lead-out portions led out from the winding portion; an element body made of a magnetic powder and a resin in which the coil is embedded; and an external electrode formed on a bottom surface which is one main surface of the element body. The lead-out portion is inclined from the winding portion toward the bottom surface of the element body in a side view of the lead-out portion viewed from a direction orthogonal to the winding axis of the coil. At least a part of a tip of the lead-out portion is exposed on the surface of the element body along the bottom surface. The tip of the lead-out portion includes a fused portion in contact with the winding portion and in which the insulating coating is joined to the outer periphery of the winding portion.

Description

Inductor

[0001] The present invention relates to an inductor.

[0002] Patent Document 1 discloses an inductor in which a coil is embedded in an element body containing a magnetic material. The coil has a lead-out portion that is bent at a right angle to the winding direction and drawn out from a wound portion formed by winding a conducting wire having a circular cross section. The lead-out portion is further bent at a right angle, so that the side surface of the conducting wire of the lead-out portion is exposed from the bottom surface of the element body and connected to an external electrode. The element body is formed by arranging the coil in a preformed body having an E-shaped cross section, covering the preformed body with a plate-shaped preformed body, and then performing compression molding.

[0003] Japanese Unexamined Patent Application Publication No. 2023-33094

[0004] In the above-mentioned conventional configuration, during compression molding of the preformed body, the lead-out portion that is bent at a right angle from the wound portion and drawn out tends to deform with the bent portion as a fulcrum, resulting in positional displacement, which may cause variation in the electrical characteristics of the inductor. In addition, since the lead-out portion bent at a right angle from the wound portion is further bent at a right angle, damage such as wrinkles, cracks, and peeling is likely to occur in the insulating coating of the conducting wire at the two bent portions, which may reduce reliability.

[0005] An object of the present invention is to provide a highly reliable inductor with little manufacturing variation in electrical characteristics by suppressing positional displacement of the coil and damage to the coil conducting wire during molding of the element body.

[0006] One aspect of the present invention is an inductor having a coil having a winding portion in which a rectangular cross-section conductor having an insulating coating is wound and two lead portions drawn out from the winding portion, a base body made of magnetic powder and resin in which the coil is embedded, and an external electrode formed on the bottom surface which is one of the main surfaces of the base body, wherein, in a side view of the lead portion viewed from a direction perpendicular to the winding axis of the coil, the lead portions are inclined toward the bottom surface of the base body from the winding portion, at least a part of the tip portion of the lead portion is exposed on the surface of the base body along the bottom surface, and the tip portion of the lead portion includes a fusion portion in which the insulating coating is joined to the outer circumference of the winding portion in contact with the winding portion. This specification shall include all the contents of Japanese Patent Application No. 2025-048228 filed on March 24, 2025.

[0007] According to the present invention, it is possible to suppress the occurrence of coil misalignment and damage to coil conductors during the molding of the base body, thereby realizing a highly reliable inductor with less manufacturing variation in electrical characteristics.

[0008] Figure 1 is a perspective view of an inductor according to one embodiment of the present invention, viewed from the top side of the base body. Figure 2 is a perspective view of the inductor viewed from the bottom side of the base body. Figure 3 is a perspective view showing the internal structure of the inductor. Figure 4 is a schematic diagram of the manufacturing process of the inductor. Figure 5 is a perspective plan view of the inductor viewed from the top side. Figure 6 is a perspective view of one side of the inductor, viewed from the direction of arrow A in Figure 3. Figure 7 is a perspective view of the other side of the inductor, viewed from the direction of arrow B in Figure 3. Figure 8 is a perspective view of the end face of the inductor, viewed from the direction of arrow C in Figure 3. Figure 9 is a diagram showing the configuration of the lead-out section according to the first modified example. Figure 10 is a diagram showing the configuration of the lead-out section according to the second modified example. Figure 11 is a perspective view showing an example of the configuration of the lead-out section according to the third modified example. Figure 12 is a perspective view of the lead-out section shown in Figure 11, viewed from the end face side of the base body. Figure 13 is a perspective view showing another example of the configuration of the lead-out section according to the third modified example. Figure 14 is a perspective view of the drawer section shown in Figure 13, viewed from the end face side of the base body. Figure 15 is a perspective view of the side of the base body showing the configuration of the drawer section according to the fifth modified example. Figure 16 is a perspective view of the side of the base body showing the configuration of the drawer section according to the sixth modified example.

[0009] Hereinafter, embodiments of the inductor according to the present invention will be described with reference to the drawings. [1. Overall configuration of the inductor] Figure 1 is a perspective view of the inductor 1 according to this embodiment, viewed from the side of the top surface 12, and Figure 2 is a perspective view of the inductor 1, viewed from the side of the bottom surface 10. The bottom surface 10 and the top surface 12 are two opposing main surfaces of the base body 2. The inductor 1 of this embodiment is configured as a surface-mount type electronic component and comprises a base body 2 in the shape of a substantially rectangular parallelepiped, which is one aspect of a substantially hexahedral shape, and a pair of external electrodes 4 provided on the surface of the base body 2.

[0010] In the following description of the base model 2, one main surface that faces the mounting substrate (not shown) during mounting is defined as the bottom surface 10, and the other main surface opposite the bottom surface 10 is called the top surface 12. A pair of outer surfaces perpendicular to the bottom surface 10 are called side surfaces 14, and a pair of outer surfaces perpendicular to the bottom surface 10 and the pair of side surfaces 14 are called end surfaces 16. The pair of side surfaces 14 are arranged facing each other. The pair of end surfaces 16 are also arranged facing each other. The bottom surface 10, top surface 12, side surfaces 14, and end surfaces 16 are each approximately rectangular in shape.

[0011] As shown in Figure 1, the distance from the bottom surface 10 to the top surface 12 is defined as the thickness T of the base body 2, the distance between the pair of end faces 16 is defined as the width W of the base body 2, and the distance between the pair of side faces 14 is defined as the length L of the base 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. That is, the bottom surface 10 and the top surface 12 are aligned with the width direction DW and the length direction DL, the side faces 14 are aligned with the width direction DW and the thickness direction DT, and the end faces 16 are aligned with the length direction DL and the thickness direction DT. Also, the side faces 14 are adjacent to the bottom surface 10, the top surface 12, and the pair of end faces 16. The end faces 16 are adjacent to the bottom surface 10, the top surface 12, and the pair of side faces 14. The nominal dimensions of the finished 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.

[0012] Hereinafter, the surface aligned with the DL and DT directions will be referred to as the LT surface, the surface aligned with the DT and DW directions as the TW surface, and the surface aligned with the DL and DW directions as the LW surface. Furthermore, the cross-sections of inductor 1 aligned with the LT surface, TW surface, and LW surface will be referred to as the LT cross-section, TW cross-section, and LW cross-section, respectively.

[0013] Figure 3 is a perspective view showing the internal structure of the inductor 1. The base body 2 comprises a coil 20 and a roughly hexahedral core 30 in which the coil 20 is embedded, and is configured as a molded inductor with the coil 20 sealed in the core 30.

[0014] The core 30 is a molded body formed by compressing a mixed powder of magnetic particles (magnetic powder) and resin into a roughly hexahedral shape by pressurizing and heating the mixture while the coil 20 is enclosed within it.

[0015] Furthermore, the magnetic particles in this embodiment are made of a soft magnetic material and contain two types of particle sizes: first magnetic particles with a relatively large average particle size and second magnetic particles with a relatively small average particle size. As a result, during compression molding, the second magnetic particles, which are small particles, are interwoven with the resin between the first magnetic particles, which are large particles, thereby increasing the filling density of the magnetic particles in the core 30 and also increasing the magnetic permeability.

[0016] Both the first and second magnetic particles are particles having a metal particle, an oxide film covering the surface of the metal particle, and an insulating film covering the surface of the oxide film. By covering the metal particle with the oxide film and insulating film, the insulation resistance and dielectric strength of the inductor are increased.

[0017] In the first magnetic particle of this embodiment, Fe-Si-B amorphous alloy powder is used as the metal particle. The oxide film of the first magnetic particle is an SiO layer and Fe ２ SiO ４ It is composed of two layers, and the overall thickness of the oxide film is between 20 nm and 155 nm. In addition, the insulating film of the first magnetic particle is made of phosphate glass with a thickness of between 10 nm and 50 nm.

[0018] Furthermore, in the second magnetic particles of this embodiment, carbonyl iron powder is used as the metal particle. The oxide film of the second magnetic particles is iron oxide formed by surface oxidation of the carbonyl iron powder, which is the metal particle. The insulating film of the second magnetic particles is a sol-gel reaction product with silica as a component. This increases the slipperiness of the surface of the second magnetic particles, making it easier for the second magnetic particles to penetrate between the first magnetic particles during the base body molding process of the base body 2, which will be described later. As a result, the density of the magnetic material in the core 30 can be further increased, and the relative permeability of the core 30 can be further increased.

[0019] The resin material contained in the mixed powder of this embodiment includes bisphenol A type epoxy resin and rubber-modified epoxy resin. This makes it possible to manufacture an inductor 1 in which both the strength and toughness of the base body 2 are improved.

[0020] As shown in Figure 3, the coil 20 comprises a winding section 22 in which a conductor is wound around a winding shaft Q, and a pair of lead-out sections 24 drawn out from the winding section 22. The winding section 22 has the conductor wound in a spiral shape along the winding shaft Q in two stages, upper and lower.

[0021] The conductor constituting the coil 20 consists of a conductor, an insulating coating covering the surface of the conductor, and a fusion layer formed on the surface of the insulating coating. The conductor is a rectangular conductor with a rectangular cross-section in the longitudinal direction. The conductor is wound so that the wide surface along one of the long sides of the rectangular cross-section is parallel to the winding axis Q. By winding the conductor while applying hot air, the fusion layers of overlapping conductors in the winding section 22 are fused and joined together.

[0022] For example, the thickness of the conductor constituting the wire is 52 μm to 118 μm, and the width is 110 μm to 180 μm. The insulating layer is made of, for example, polyimide amide resin and has a thickness of 3 μm. The fusion layer is made of, for example, polyamide resin and has a thickness of 1 μm to 25 μm.

[0023] The coil 20 is embedded within the base body 2 such that the winding shaft Q of the winding section 22 is aligned with the thickness direction DT of the base body 2. That is, the winding shaft Q is perpendicular to the bottom surface 10 and the top surface 12 and extends in a direction along the side surface 14 and the end surface 16. Each of the lead-out sections 24 is drawn out from the winding section 22 toward the bottom surface 10 of the base body 2 and connected to the external electrode 4.

[0024] The configuration of coil 20 will be explained further later.

[0025] A protective layer (not shown) is formed on the surface of the substrate 2, excluding the area of ​​the external electrode 4. The protective layer is, for example, a resin obtained by adding phenoxy resin to a novolac resin, and contains nanosilica as a filler. As an example, the thickness of the protective layer is 10 μm or more and 30 μm or less.

[0026] Inductor 1 with this configuration can improve DC superposition characteristics by using soft magnetic material for the magnetic particles, and is therefore used as an electronic component in electrical circuits where large currents flow, as 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, and medical and industrial machinery. However, the applications of inductor 1 are not limited to these, and it can also be used in tuning circuits, filter circuits, and rectifier / smoothing circuits, for example.

[0027] [2. Overview of the Inductor Manufacturing Process] Figure 4 is an overview of the manufacturing process of inductor 1. As shown in the figure, the manufacturing process of inductor 1 includes a coil formation process, a pre-molded body formation process, a base body molding process, a base body grinding process, and an external electrode formation process.

[0028] The coil formation process is a process of forming a coil 20 from a conductor wire. In this process, the coil 20 is formed in the shape having the aforementioned winding portion 22 and lead portion 24 by winding the conductor wire using a winding method called "alpha winding". Alpha winding refers to a state in which the conductor wire, which functions as a conductor, is wound in a spiral shape in two stages such that the lead portions 24 at the beginning and end of the winding are located on the outer circumference. The number of turns of the coil 20 is not particularly limited.

[0029] The pre-molded body formation process is a process for forming pre-molded bodies called tablets. The pre-molded bodies are formed by pressurizing the mixed powder, which is the material for the base body 2, to form a solid that is easy to handle. In this embodiment, two types of tablets are formed: a first tablet with an appropriate shape (for example, a shape with an E-shaped or T-shaped cross-section) on which the coil 20 is placed, and a second tablet with an appropriate shape (for example, a plate-shaped or rectangular parallelepiped with an opening) that sandwiches the coil 20 between the first tablet and the first tablet.

[0030] In the base body molding process, the first tablet, coil, and second tablet are set in a molding die, and while applying heat, pressure is applied in the direction in which the first and second tablets overlap, causing the tablets to deform and harden, thereby integrating the first tablet, coil, and second tablet. This forms a base body 2 with the coil 20 enclosed in the core 30. In addition, barrel polishing may be performed on the base body 2 obtained in this process to remove burrs and other defects, or to chamfer the corners of the base body 2.

[0031] The base body grinding process involves grinding the bottom surface 10 and top surface 12 of the base body 2 to expose the lead portion 24 of the coil 20 to the bottom surface 10, and adjusting the thickness T of the base body 2.

[0032] The external electrode formation step is a step of forming an external electrode 4 on the surface of the base body 2, and includes a base body protective layer formation step, a surface treatment step, and a plating layer formation step.

[0033] The base body protective layer formation process involves coating the entire surface of the base body 2 with an insulating resin.

[0034] The surface treatment process involves modifying the surface of the electrode area on the core 30 by irradiating it with laser light. Here, the electrode area refers to the area on the surface of the core 30 where the external electrode 4 should be formed, and includes the portion where the electrode connection region 23b is exposed. Specifically, by irradiating with laser light, the protective layer on the surface of the base body 2 and the coating layer of the electrode connection region 23b of the coil 20 are removed in the area of ​​the electrode area, as well as the resin on the surface of the core 30 and the insulating film on the surface of the magnetic particles exposed from the core 30. As a result, the area of ​​exposed metal of the magnetic particles per unit area of ​​the surface of the core 30 is larger in the electrode area compared to other parts of the core 30 surface. After irradiation with laser light, a cleaning process (e.g., etching) may be performed to clean the surface of the electrode area.

[0035] In the plating layer formation process, copper is barrel-plated onto the surface of the core 30 to form a copper plating layer at the electrode location where the laser beam will be irradiated. In addition, a Ni plating layer and an Sn plating layer may be further formed on top of the copper plating layer.

[0036] [3. Detailed Configuration of the Inductor] The details of the inductor 1 in this embodiment will be further explained below. In the conventional inductor exemplified in Patent Document 1, the lead portion drawn out from the coil winding portion has no support until the coil is embedded in the base body after the base body molding process. Therefore, it is easily deformed by the compressive force applied to the pre-molded body during the base body molding process, and electrical characteristics are prone to variation due to manufacturing variations. Also, as shown in Patent Document 1, in the case of a lead portion formed by bending the conductor at a right angle from the winding portion, the insulating coating of the conductor is prone to damage such as wrinkles, cracks, and peeling, which can reduce reliability.

[0037] In contrast, in the inductor 1 according to this embodiment, the lead portion 24 is led out from the winding portion 22 so as to be inclined toward the bottom surface 10, and at least a part of the lead portion 24 is in contact with the winding portion 22 and joined to the conductor of the winding portion 22. As a result, in the inductor 1, damage to the insulating coating of the conductor is prevented, and deformation of the lead portion 24 during the molding process is prevented or suppressed.

[0038] Figure 5 is a perspective view of the inductor 1 as seen from the top surface 12. Figure 6 is a perspective view of one side surface 14 of the inductor 1 as seen from the direction of arrow A in Figure 3, and Figure 7 is a perspective view of the other side surface 14 of the inductor 1 as seen from the direction of arrow B in Figure 3. Figure 8 is a perspective view of the end surface 16 of the inductor 1 as seen from the direction of arrow C in Figure 3. Note that in Figures 5, 6, 7, and 8, the coil 20 inside the main body 2 is shown with a solid line for ease of understanding.

[0039] As shown in Figures 6 and 7, in the inductor 1, the lead portion 24, when viewed from a side view of the lead portion 24 from a direction perpendicular to the winding axis of the coil 20 (in this embodiment, a side view from a direction perpendicular to the side surface 14), includes an inclined portion 25 that slopes from the winding portion 22 toward the bottom surface 10 of the base body 2, and a tip portion 26 that curves from the inclined portion 25 to the end 27 of the lead portion 24. Here, the boundary between the winding portion 22 and the lead portion 24 is the portion where the direction of extension of the conductor begins to curve from the winding direction of the conductor in the winding portion 22 (the horizontal direction shown in the figure), that is, the portion shown by the dashed line in Figures 6 and 7. Also, the boundary between the inclined portion 25 and the tip portion 26 is the portion where the direction of extension of the conductor begins to curve from the direction of extension of the inclined portion 25, that is, the portion shown by the dashed line in Figures 6 and 7.

[0040] Furthermore, one side of the conductor at the tip portion 26 is exposed on the surface of the base body 2 along the bottom surface 10. The tip portion 26 also contacts the winding portion 22 and includes a fused portion F (hatched portion shown in Figures 6 and 7) where the insulating coating is joined to the outer circumference of the winding portion 22.

[0041] Herein, in this specification, unless otherwise specified, one surface of a conductor is not limited to a surface along one of the four sides of the rectangle formed by the cross-section of a conductor having a rectangular cross-section, but may also be a surface newly created on a part of the conductor when a conductor exposed on the bottom surface 10 or a conductor arranged in the surface layer of the bottom surface 10 inside the base body 2 is ground together with the bottom surface 10 in the base body grinding process described above.

[0042] In the inductor 1 having the above configuration, the lead portion 24 is not bent at a right angle from the winding portion 22 but is drawn out at an inclination toward the bottom surface 10, thereby preventing or suppressing damage to the insulating coating of the conductors constituting the coil 20. Furthermore, since the lead portion 24 is joined to the outer circumference of the winding portion 22 at the fused portion F of the tip portion 26, which is a part of it, deformation of the lead portion 24 during the molding process is prevented or suppressed. As a result, the inductor 1 can suppress misalignment of the coil 20 and damage to the conductors of the coil 20 during molding, thereby suppressing manufacturing variations in electrical characteristics and achieving high reliability.

[0043] When distinguishing the two side views shown in FIG. 6 and FIG. 7, suffixes a and b shall be added to the components in each side view, respectively. That is, the side surface 14, lead-out portion 24, inclined portion 25, tip portion 26, terminal end 27, and fused portion F in the side view shown in FIG. 6 are referred to as side surface 14a, lead-out portion 24a, inclined portion 25a, tip portion 26a, terminal end 27a, and Fa, respectively; and the side surface 14, lead-out portion 24, inclined portion 25, tip portion 26, terminal end 27, and fused portion F in the side view shown in FIG. 7 are referred to as side surface 14b, lead-out portion 24b, inclined portion 25b, tip portion 26b, terminal end 27b, and fused portion Fb, respectively.

[0044] In one side view shown in FIG. 6, the lead-out portion 24a is drawn out while being inclined toward the bottom surface 10 by the inclined portion 25a from the upper stage (the stage farther from the bottom surface 10) of the winding portion 22 wound in two stages as illustrated, and the tip portion 26a is joined to the outer circumference of the lower stage (the stage closer to the bottom surface 10) of the winding portion 22 as illustrated by the fused portion Fa. Further, the lower surface of the tip portion 26a as illustrated is exposed on the bottom surface 10 and connected to one external electrode 4.

[0045] Further, in the other side view shown in FIG. 7, the lead-out portion 24b is drawn out while being inclined toward the bottom surface 10 by the inclined portion 25b from the lower stage of the winding portion 22 wound in two stages as illustrated, and the tip portion 26b is joined to the outer circumference of the lower stage of the winding portion 22 as illustrated by the fused portion Fb. Further, the lower surface of the tip portion 26b as illustrated is exposed on the bottom surface 10 and connected to the other external electrode 4.

[0046] From the viewpoint of effectively suppressing deformation of the lead-out portion 24 during element molding, it is preferable that the width h of the fused portion F measured in a direction perpendicular to the extending direction of the conductive wire of the winding portion 22 is in a range of 1 / 4 or more and 1 / 2 or less of the width H of the conductive wire. The fused portion F does not necessarily have to be rectangular as shown in FIG. 6 and FIG. 7, and may have an irregular shape in which the width h of the fused portion F changes along the extending direction of the tip portion 26. Also in this case, it is preferable that the width h of the fused portion F changes within the above range.

[0047] Furthermore, from the viewpoint of reducing the DC resistance value at the connection between the lead-out portion 24 and the external electrode 4, the exposed length w of the tip portion 26 exposed from the bottom surface 10 is preferably not less than 1 / 4 and not more than 3 / 4 of the minimum value Wmin of the distance between outer peripheries of the wound portion 22 measured in a direction orthogonal to the winding axis Q. In FIGS. 6 and 7, as an example, the minimum value Wmin of the distance between the outer peripheries of the wound portion 22 is the width of the wound portion 22 measured in the illustrated horizontal direction corresponding to the DW direction.

[0048] It should be noted that, in the two side views shown in FIGS. 6 and 7, the values of the respective widths h of the fused portions Fa and Fb may be different from each other or may be the same. Further, in the two side views shown in FIGS. 6 and 7, the respective exposed lengths w of the tip portion 26a and the tip portion 26b may be different from each other or may be the same. In addition, the boundary between the wound portion 22 and the lead-out portion 24 does not need to be clearly distinguishable as illustrated, and the fused portion F may be provided on the inclined portion 25 of the lead-out portion 24.

[0049] Hereinafter, modified examples of the coil 20 that can be used for the inductor 1 will be described. FIG. 9 is a diagram showing a configuration of the lead-out portion 24 in the coil 20 as a first modified example. FIG. 9 is a see-through plan view of the inductor 1 viewed from the upper surface 12 side, and corresponds to FIG. 5. In the first modified example, in a plan view viewed from a direction orthogonal to the bottom surface 10 of the element body 2 (that is, the plan view shown in FIG. 9), the two tip portions 26 each have a separating portion 261 extending in a direction away from each other toward the respective distal end 27 of the tip portion 26. In FIG. 9, the tip portions 26a and 26b respectively have separating portions 261a and 261b extending in directions away from each other toward the distal ends 27a and 27b, respectively. According to this configuration, the position of the coil 20 within the element body 2 can be maintained more stably in the element body molding step.

[0050] Figure 10 shows the configuration of the lead portion 24 in the coil 20 as a second modification. Figure 10 is a perspective plan view of the inductor 1 viewed from the top surface 12 side, and corresponds to Figure 5. In the second modification, in a plan view viewed from a direction perpendicular to the bottom surface 10 of the base body 2 (i.e., the plan view shown in Figure 10), the two tip portions 26 each have approach portions 262 that extend toward each other toward the respective ends 27 of the tip portion 26. In Figure 10, the tip portions 26a and 26b each have approach portions 262a and 262b that extend toward each other toward the ends 27a and 27b, respectively. With this configuration, the average distance between the lead portion 24 and the side surface 14 along the extending direction of the lead portion 24 can be increased, so the size of the inductor 1 can be reduced.

[0051] In the first modified example shown in Figure 9 and the second modified example shown in Figure 10, the fused portion F is included in the portion of the tip portion 26 excluding the separated portion 261 and the portion excluding the approaching portion 262, respectively. In this case as well, from the viewpoint of bonding the lead portion 24 to the winding portion 22 with sufficient strength, it is preferable that the width h of the fused portion F measured in a direction perpendicular to the extending direction of the conductor of the winding portion 22 is in the range of 1 / 4 to 1 / 2 of the width H of the conductor.

[0052] Furthermore, in the first modified example shown in Figure 9 and the second modified example shown in Figure 10, from the viewpoint of reducing the DC resistance value at the connection between the lead portion 24 and the external electrode 4, it is preferable that the exposed length w of the tip portion 26 exposed from the bottom surface 10 is 1 / 4 or more and 3 / 4 or less of the minimum value Wmin of the distance between the outer circumferences of the winding portion 22 measured in a direction perpendicular to the winding shaft Q.

[0053] As a third modification of the coil 20, the tip portion 26 of the lead portion 24 is twisted clockwise or counterclockwise at an angle of 90 degrees or less toward the end portion 27 of the tip portion 26, and one surface of the twisted portion of the tip portion 26 is exposed from the bottom surface. As a result, the contact area between the tip portion 26 of the lead portion 24 and the external electrode 4 is increased, and the DC resistance of the inductor 1 can be reduced.

[0054] Figures 11 and 12 show an example of the configuration of a third modified example. Figure 11 is a perspective view showing the inside of the inductor 1 and corresponds to Figure 3. Figure 12 is a perspective view of the end face 16 of the inductor 1 viewed from the direction of arrow C1 shown in Figure 11 and corresponds to Figure 8. The tip portion 26a is twisted at an angle of approximately 20 degrees counterclockwise toward the end portion 27a (i.e., counterclockwise toward the plane normal direction of Figure 12; therefore, clockwise in Figure 12 viewed from the opposite direction to the normal direction), and one surface of the twisted portion of the tip portion 26a is exposed from the bottom surface 10 and connected to one external electrode 4. The tip portion 26b is twisted at an angle of approximately 20 degrees clockwise toward the end portion 27b (therefore, counterclockwise in Figure 12), and one surface of the twisted portion of the tip portion 26b is exposed from the bottom surface 10 and connected to the other external electrode 4.

[0055] Figures 13 and 14 show another example of the configuration of the third modified example. Figure 13 is a perspective view showing the inside of the inductor 1 and corresponds to Figure 3. Figure 14 is a perspective view of the end face 16 of the inductor 1 viewed from the direction of arrow C2 shown in Figure 13 and corresponds to Figure 8. The tip portion 26a is twisted at an angle of approximately 20 degrees clockwise (and therefore counterclockwise in Figure 14) toward the end portion 27a, and one surface of the twisted portion of the tip portion 26a is exposed from the bottom surface 10 and connected to one of the external electrodes 4. The tip portion 26b is twisted at an angle of approximately 20 degrees counterclockwise (and therefore clockwise in Figure 14) toward the end portion 27b, and one surface of the twisted portion of the tip portion 26b is exposed from the bottom surface 10 and connected to the other external electrode 4.

[0056] The tip portions 26a and 26b may both be twisted clockwise, or they may both be twisted counterclockwise.

[0057] In the third modified example, the tip portion 26 also includes a fused portion F in which the insulating coating is joined to the outer circumference of the winding portion 22. In this case as well, from the viewpoint of bonding the lead portion 24 to the winding portion 22 with sufficient strength, it is preferable that the width h of the fused portion F, measured in a direction perpendicular to the direction in which the conductor of the winding portion 22 extends, is in the range of 1 / 4 to 1 / 2 of the width H of the conductor.

[0058] Furthermore, in the third modified example, from the viewpoint of reducing the DC resistance value at the connection between the lead portion 24 and the external electrode 4, it is preferable that the exposed length w of the tip portion 26 exposed from the bottom surface 10 is 1 / 4 or more and 3 / 4 or less of the minimum value Wmin of the distance between the outer circumferences of the winding portion 22 measured in a direction perpendicular to the winding shaft Q.

[0059] Figure 15 shows the configuration of the lead portion 24 in the coil 20 as a fourth modification. Figure 15 is a side view of the lead portion 24a viewed from a direction perpendicular to the winding shaft Q, and corresponds to Figure 6. In the fourth modification, in a side view of the tip portion 26a viewed from a direction perpendicular to the winding shaft Q (in this embodiment, a side view viewed from a direction perpendicular to the side surface 14a), the tip portion 26a includes a first portion 263a extending along the bottom surface 10, and a second portion 264a extending away from the bottom surface 10 from the end of the first portion 263a toward the end 27a of the tip portion 26a. One surface of the first portion 263a is exposed to the bottom surface 10 and connected to one of the external electrodes 4. The lead portion 24b is configured similarly to the lead portion 24a.

[0060] According to this, the thickness of the base body can be reduced, and the thickness of the inductor 1 can be reduced.

[0061] In the fourth modified example shown in Figure 15, the first portion 263a of the tip portion 26a includes a fused portion F in which the insulating coating is joined to the outer circumference of the winding portion 22. In this case as well, from the viewpoint of bonding the lead portion 24 to the winding portion 22 with sufficient strength, it is preferable that the width h of the fused portion F, measured in a direction perpendicular to the direction of extension of the conductor of the winding portion 22, is in the range of 1 / 4 to 1 / 2 of the width H of the conductor. The same applies to the tip portion 26b.

[0062] Furthermore, in the case of the fourth modified example, from the viewpoint of reducing the DC resistance value at the connection between the lead-out portion 24a and the external electrode 4, it is preferable that the exposed length w of the tip portion 26a exposed from the bottom surface 10 is 1 / 4 to 3 / 4 of the minimum value Wmin of the distance between the outer circumferences of the winding portion 22 measured in a direction perpendicular to the winding shaft Q. The same applies to the tip portion 26b.

[0063] Figure 16 shows the configuration of the lead portion 24 in the coil 20 as a fifth modification. Figure 16 is a side view of the lead portion 24a viewed from a direction perpendicular to the winding shaft Q, and corresponds to Figure 6. In the fifth modification, in a side view of the tip portion 26a viewed from a direction perpendicular to the winding shaft Q (in this embodiment, a side view viewed from a direction perpendicular to the side surface 14a), the tip portion 26a includes a third portion 265a extending along a plane parallel to the bottom surface 10, and a fourth portion 266a extending from the end of the third portion 265a toward the end 27 of the tip portion 26 toward the bottom surface 10. One surface of the end 27a of the tip portion 26a is exposed to the bottom surface 10 and connected to one of the external electrodes 4. The lead portion 24b is configured similarly to the lead portion 24a.

[0064] According to this, when the bottom surface 10 is ground during the base material grinding process, the end 27a of the pull-out portion 24a can be reliably exposed to the bottom surface 10 and connected to the external electrode 4. The same applies to the pull-out portion 24b.

[0065] In the fifth modified example shown in Figure 16, the third portion 265a of the tip portion 26a includes a fused portion Fa in which the insulating coating is joined to the outer circumference of the winding portion 22. In this case as well, from the viewpoint of bonding the lead portion 24a to the winding portion 22 with sufficient strength, it is preferable that the width h of the fused portion Fa, measured in a direction perpendicular to the extending direction of the conductor of the winding portion 22, is in the range of 1 / 4 to 1 / 2 of the width H of the conductor. The same applies to the tip portion 26b.

[0066] [4. Other Embodiments] The characteristic features of the coil 20 shown in the embodiments described above and the first, second, third, fourth, fifth, and sixth modified examples can be combined and used in a single inductor 1 within a range that does not contradict each other. This makes it possible to have the effects described for each combined modified example in a single inductor 1. For example, by combining the characteristic configurations of the coil 20 shown in the first modified example and the third modified example, the separated portion 261 shown in Figure 9 may be twisted clockwise or counterclockwise at an angle of 90 degrees or less toward the end of the tip portion 26. This makes it possible to maintain the position of the coil 20 within the base body 2 in the base body molding process more stably, while increasing the contact area between the tip portion 26 and the external electrode 4 and lowering the DC resistance of the inductor 1.

[0067] All embodiments and modifications described above are illustrative of one aspect of the present invention and can be arbitrarily modified and applied without departing from the spirit of the invention. Furthermore, any elements of the embodiments described above can be combined to create new embodiments. In addition, unless otherwise specified, the directions such as horizontal, orthogonal, and vertical, as well as various numerical values, shapes, and materials in the embodiments described above, include a range that produces the same effect as those directions, numerical values, shapes, and materials (a so-called equivalent range).

[0068] [5. Configurations Supported by the Above Embodiments] The above embodiments support the following configurations.

[0069] (Configuration 1) An inductor having a coil having a winding portion in which a rectangular cross-section conductor having an insulating coating is wound and two lead portions drawn out from the winding portion, a base body made of magnetic powder and resin in which the coil is embedded, and an external electrode formed on the bottom surface which is one of the main surfaces of the base body, wherein, in a side view of the lead portion viewed from a direction perpendicular to the winding axis of the coil, the lead portions are inclined toward the bottom surface of the base body from the winding portion, at least a part of the tip portion of the lead portion is exposed on the surface of the base body along the bottom surface, and the tip portion of the lead portion includes a fusion portion in which the insulating coating is joined to the outer circumference of the winding portion in contact with the winding portion. With this configuration, it is possible to suppress the occurrence of misalignment of the coil and damage to the coil conductor during base body molding, thereby realizing a highly reliable inductor with less manufacturing variation in electrical characteristics.

[0070] (Configuration 2) The inductor according to Configuration 1, wherein the winding portion is wound in two stages along the winding shaft and has a lower stage closer to the bottom surface of the base body and an upper stage further from the bottom surface, and one of the two lead-out portions drawn out from the winding portion is drawn out from the upper stage and joined to the outer circumference of the lower stage, and the other lead-out portion is drawn out from the lower stage and joined to the outer circumference of the lower stage. With this configuration, for example, two lead-out portions drawn out from a winding portion wound in two stages by alpha winding or the like can be easily joined to the outer circumference of the winding portion.

[0071] (Configuration 3) In a plan view taken from a direction perpendicular to the bottom surface of the base body, the two tip portions of the two lead portions each have a separated portion that extends toward the respective end of the tip portion toward each other, the inductor according to Configuration 1 or 2. With this configuration, the position of the coil within the base body during molding can be maintained more stably.

[0072] (Configuration 4) The inductor according to Configuration 1 or 2, wherein, in a plan view taken from a direction perpendicular to the bottom surface of the base body, the two tip portions of the two lead portions each have approaching portions that extend toward each other toward the respective ends of the tip portions. With this configuration, the average distance between the lead portion and the side surface of the base body along the extending direction of the lead portion can be increased, so the size of the inductor can be reduced.

[0073] (Configuration 5) The inductor according to any one of Configurations 1 to 4, wherein the tip portion of the lead-out section is twisted clockwise or counterclockwise at an angle of 90 degrees or less toward the end of the tip portion, and one surface of the twisted portion of the tip portion is exposed from the bottom surface. With this configuration, the contact area between the tip portion of the lead-out section and the external electrode is increased, so the DC resistance of the inductor can be reduced.

[0074] (Configuration 6) In a side view of the tip portion viewed from a direction perpendicular to the winding shaft, the tip portion includes a first portion extending along the bottom surface and a second portion extending from the end of the first portion toward the end of the tip portion toward the bottom surface, wherein one surface of the first portion of the tip portion is exposed from the bottom surface, as described in any configuration 1 to 5. This configuration allows for a reduction in the thickness of the base body.

[0075] (Configuration 7) An inductor according to any one of Configurations 1 to 6, wherein the exposed length of the tip portion exposed from the bottom surface is 1 / 4 or more and 3 / 4 or less of the minimum distance between the outer circumferences of the winding portion measured in a direction perpendicular to the winding shaft. With this configuration, the contact area between the lead portion and the external electrode can be secured, and the DC resistance of the inductor can be reduced.

[0076] (Configuration 8) In a side view of the tip portion viewed from a direction perpendicular to the winding shaft, the tip portion includes a third portion extending along a plane parallel to the bottom surface, and a fourth portion extending from the end of the third portion toward the end of the tip portion toward the bottom surface, wherein one surface of the end of the tip portion is exposed to the bottom surface, as described in any configuration 1 to 5. With this configuration, the bottom surface of the base body can be ground to reliably expose the end of the lead portion to the bottom surface and connect it to an external electrode.

[0077] (Configuration 9) The inductor according to any one of Configurations 1 to 8, wherein the fused portion including the tip portion of the lead-out portion has a width that contacts the winding portion along the direction of the winding shaft, and is in the range of 1 / 4 to 1 / 2 of the width of the tip portion along the direction of the winding shaft. With this configuration, deformation of the lead-out portion during molding can be effectively suppressed.

[0078] 1...Inductor, 2...Base, 4...External electrode, 10...Bottom surface, 12...Top surface, 14, 14a, 14b...Side surface, 16...End surface, 20...Coil, 22...Winding section, 24, 24a, 24b...Outer section, 25, 25a, 25b...Inclined section, 26, 26a, 26b...Tip section, 27, 27a, 27b...End, 30...Core, 261, 261a, 261b...Separated section, 262, 262a, 262b...Approaching section, 263a...First section, 264a...Second section, 265a...Third section, 266a...Fourth section, F, Fa, Fb...Fused section, Q...Winding shaft.

Claims

1. An inductor comprising: a coil having a winding portion around which a rectangular cross-section conductor having an insulating coating is wound, and two lead portions drawn out from the winding portion; a base body made of magnetic powder and resin in which the coil is embedded; and an external electrode formed on the bottom surface, which is one of the main surfaces of the base body, wherein, in a side view of the lead portion viewed from a direction perpendicular to the winding axis of the coil, the lead portions are inclined toward the bottom surface of the base body from the winding portion, at least a portion of the tip of the lead portion is exposed on the surface of the base body along the bottom surface, and the tip of the lead portion includes a fusion portion in which the insulating coating is joined to the outer circumference of the winding portion in contact with the winding portion.

2. The inductor according to claim 1, wherein the winding portion is wound in two stages along the winding shaft and has a lower stage closer to the bottom surface of the base body and an upper stage further from the bottom surface, and one of the two lead-out portions drawn out from the winding portion is drawn out from the upper stage and joined to the outer circumference of the lower stage, and the other lead-out portion is drawn out from the lower stage and joined to the outer circumference of the lower stage.

3. In a plan view taken from a direction perpendicular to the bottom surface of the base body, the two tip portions of the two lead portions each have a separated portion that extends toward the respective end of the tip portion toward each other.

4. In a plan view taken from a direction perpendicular to the bottom surface of the main body, the two tip portions of the two lead portions each have approaching portions that extend toward each other toward the respective ends of the tip portions, the inductor according to claim 1 or 2.

5. The inductor according to any one of claims 1 to 4, wherein the tip portion of the lead-out is twisted clockwise or counterclockwise at an angle of 90 degrees or less toward the end of the tip portion, and one surface of the twisted portion of the tip portion is exposed from the bottom surface.

6. In a side view of the tip portion viewed from a direction perpendicular to the winding shaft, the tip portion includes a first portion extending along the bottom surface and a second portion extending away from the bottom surface from the end of the first portion toward the end of the tip portion, wherein one surface of the first portion of the tip portion is exposed from the bottom surface, the inductor according to any one of claims 1 to 5.

7. The inductor according to any one of claims 1 to 6, wherein the exposed length of the tip portion exposed from the bottom surface is 1 / 4 or more and 3 / 4 or less of the minimum distance between the outer circumferences of the winding portion measured in a direction perpendicular to the winding shaft.

8. In a side view of the tip portion viewed from a direction perpendicular to the winding shaft, the tip portion includes a third portion extending along a plane parallel to the bottom surface, and a fourth portion extending from the end of the third portion toward the end of the tip portion toward the bottom surface, wherein one face of the end of the tip portion is exposed to the bottom surface, the inductor according to any one of claims 1 to 5.

9. The inductor according to any one of claims 1 to 8, wherein the fused portion, which includes the tip portion of the lead-out portion, has a width that contacts the winding portion along the direction of the winding shaft, and is in the range of 1 / 4 to 1 / 2 of the width of the tip portion along the direction of the winding shaft.

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