Inductor and method for manufacturing inductor

Abstract

The present invention provides an inductor in which the wall thickness of a core part between an outer peripheral surface of a coil and an outer surface of an element body can be easily adjusted.　Provided is an inductor including an element body having a core part containing metal magnetic powder and resin, and a coil embedded inside the core part. The core part has a first core part having a columnar part and a plate-like part, and a second core part covering the first core part. The coil has a wound part in which a conductive wire is wound and a pair of lead parts drawn out from the wound part toward the outer peripheral side of the wound part. At least a part of the wound part protrudes further to the outer peripheral side than an outer peripheral surface of the plate-like part. The second core part has a proximity outer peripheral surface that is an outer peripheral surface to which the lead parts of the coil approach, and a non-proximity outer peripheral surface that is an outer peripheral surface of a portion different from the proximity outer peripheral surface. The second core part is formed such that the distance between the non-proximity outer peripheral surface and an outer peripheral surface of the first core part is greater than the distance between the non-proximity outer peripheral surface and the outer peripheral surface of the wound part of the coil.

Description

Inductor and method for manufacturing inductor

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

[0002] Patent Document 1 discloses a composite inductor including a magnetic base, a coil structure disposed on the magnetic base, and a package structure covering the magnetic base and the coil structure as a configuration related to an inductor. That is, Patent Document 1 describes a composite inductor in which a coil structure having a size that does not protrude radially from the magnetic base is disposed on an assembly surface of the magnetic base, and the magnetic base and the coil structure are covered with the package structure. In Patent Document 1, a coil structure and a first magnetic body are disposed in a cavity of a mold, then powder for forming a second magnetic body is filled, and the mold is hot-pressed, whereby the first magnetic body, the second magnetic body and the coil structure are integrated to constitute the composite inductor.

[0003] Further, Patent Document 2 discloses a method for manufacturing an inductor. In Patent Document 2, a lower core is formed by filling magnetic powder into a molding die formed by a mold frame, an upper punch and a lower punch above and below the mold frame, and performing compression molding. Then, Patent Document 2 discloses that a coil is placed on the lower core in the molding die, and thereafter, magnetic powder is filled so that the coil is embedded and compression molding is performed, thereby manufacturing a powder compact core with embedded coil. Patent Document 2 also discloses forming an E-core-shaped lower core, placing the coil on the lower core, and finally manufacturing the coil-embedded powder compact core.

[0004] U.S. Patent Application Publication No. 2024 / 0194388 Japanese Unexamined Patent Publication No. 2001-267160

[0005] In the inductor having the configuration of Patent Document 1, magnetic particles are filled into the gap between the mold and the outer circumference of the coil. Therefore, in order to reduce the wall thickness of the core portion between the outer surface of the coil and the outer surface of the substrate, it is necessary to bring the outer surface of the coil and the inner surface of the molding mold close together. As a result, if the coil is misaligned, the outer surface of the coil and the molding mold are more likely to come into contact, hindering the filling of magnetic material between the outer surface of the coil and the molding mold. Thus, in the inductor having the above configuration, there was a problem in that it was difficult to adjust the wall thickness of the core portion between the outer surface of the coil and the outer surface of the substrate.

[0006] In the inductor having the configuration of Patent Document 2, the magnetic powder is filled after the coil is placed, so there is a possibility that the coil may be pushed by the magnetic powder and shift position when the magnetic powder is filled, and there is room for further improvement in setting the position of the coil. Also, in general, in inductors, it is desirable to make it easy to adjust the wall thickness of the core portion between the outer surface of the coil and the outer surface of the element for electrical characteristics.

[0007] A first aspect of the present invention is an inductor comprising a body having a core portion containing metal magnetic powder and resin, and a coil embedded inside the core portion, wherein the core portion has a first core portion having a columnar portion and a plate-shaped portion, and a second core portion covering the first core portion, the coil has a winding portion around which a conductor is wound, and a pair of lead portions drawn out from the winding portion to the outer circumference of the winding portion, at least a part of the winding portion protrudes outward from the outer circumference of the plate-shaped portion, the second core portion has a close outer circumference surface which is the outer circumference surface in close proximity to the lead portions of the coil, and a non-close outer circumference surface which is the outer circumference surface of a portion different from the close outer circumference surface, and the second core portion is formed such that the distance between the non-close outer circumference surface and the outer circumference surface of the first core portion is greater than the distance between the non-close outer circumference surface and the outer circumference surface of the winding portion of the coil. A second aspect of the present invention is a method for manufacturing an inductor comprising a base body having a core portion containing metal magnetic powder and resin, and a coil embedded inside the core portion, comprising: a first pre-molded body preparation step of preparing a first pre-molded body containing metal magnetic powder and resin and having a columnar portion and a plate portion; a second pre-molded body preparation step of preparing a second pre-molded body having a recess on its upper surface due to an upwardly protruding wall, in a molding die with the recess facing upward; and a winding portion wound around the columnar portion of the first pre-molded body, which is the plate portion of the first pre-molded body. A method for manufacturing an inductor, comprising: a coil forming step of forming the coil having a winding portion that protrudes outward from the outer peripheral surface of the shaped portion; a first pre-molded body placement step of arranging the first pre-molded body so that the winding portion of the coil provided on the first pre-molded body is accommodated in the recess of the second pre-molded body; and a body forming step of thermally compressing the first pre-molded body and the second pre-molded body in a molding die to form the base body having a first core portion having the columnar portion and the plate portion and a second core portion covering the first core portion.A third aspect of the present invention is a method for manufacturing an inductor comprising a base body having a core portion containing metal magnetic powder and resin, and a coil embedded inside the core portion, comprising: a first pre-molded body preparation step of preparing a first pre-molded body containing metal magnetic powder and resin, having a plate-like portion and a columnar portion formed on the plate-like portion; a second pre-molded body forming step of filling a molding die with the pre-molded body material containing metal magnetic powder and resin, softening the pre-molded body material by heating, and then inserting a jig into the molding die to form a recess on the surface of the softened pre-molded body material, thereby forming a second pre-molded body having the recess and a peripheral wall provided around the recess; and the first pre-molded body A method for manufacturing an inductor, comprising: a coil mounting step of mounting the coil such that the columnar portion of the first pre-molded body is inserted into the winding portion of the coil; a first pre-molded body mold housing step of housing the first pre-molded body with the coil mounted on it into the molding die such that the outer circumference of the winding portion of the coil is close to the inner surface of the surrounding wall of the second pre-molded body; and a body forming step of thermally compressing the first pre-molded body and the second pre-molded body in the molding die to form a body having a core portion having a plate-like portion and a columnar portion formed on the plate-like portion, a second core portion covering the first core portion, and the coil embedded inside the core portion. This specification shall include all the contents of Japanese Patent Application No. 2025-027690, filed on February 25, 2025, and all the contents of Japanese Patent Application No. 2025-027691, filed on February 25, 2025.

[0008] According to the present invention, it is possible to provide an inductor in which the wall thickness of the core portion between the outer surface of the coil and the outer surface of the element can be easily adjusted. Furthermore, according to the present invention, it is possible to provide an inductor in which the wall thickness of the core portion between the outer surface of the coil and the outer surface of the element can be easily adjusted while accurately setting the position of the coil.

[0009] Figure 1 is a perspective view of the inductor according to the first embodiment, viewed from the top. Figure 2 is a perspective plan view showing the internal structure of the inductor according to the first embodiment. Figure 3 is a schematic diagram corresponding to the cross-section by line III-III in Figure 2. Figure 4 is an overview diagram of the manufacturing process of the inductor according to the first embodiment. Figure 5 is a perspective view showing the state in which the coil conductor of the first pre-molded body is placed in the recess of the second pre-molded body. Figure 6 is a plan view showing the state in Figure 5. Figure 7 is a cross-sectional view showing the inside of the molding die corresponding to the cross-section by line VII-VII in Figure 6. Figure 8 is a diagram showing a part of the manufacturing method of the inductor according to the second embodiment. Figure 9 is an overview diagram of the manufacturing process of the inductor according to the third embodiment. Figure 10 is an explanatory diagram of the preparation process for the second pre-molded body. Figure 11 is a vertical cross-sectional view of Figure 10. Figure 12 is a diagram showing the size relationship between the formation recess of the molding die and the jig of the pressurizing jig member. Figure 13 is a diagram showing a part of the manufacturing method of the inductor according to the fourth embodiment. Figure 14 is a diagram showing another embodiment.

[0010] Embodiments of the present invention will be described below with reference to the drawings.

[0011] [1. First Embodiment] [Overall Configuration of Inductor] Figure 1 is a perspective view of the inductor 1 according to the first embodiment, viewed from the top surface 12. The inductor 1 of this embodiment is configured as a surface-mount type electronic component. The inductor 1 of this embodiment comprises a substantially rectangular parallelepiped base body 2, which is one aspect of a substantially hexahedral shape, and two external electrode portions (not shown) provided on the surface of the base body 2.

[0012] In the following, in the base body 2, the first main surface that faces the 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. Furthermore, a pair of third main surfaces perpendicular to the bottom surface 10 are defined as end surfaces 14. In addition, 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.

[0013] 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 side surfaces 16 is defined as the width W of the base body 2, and the distance between the pair of end surfaces 14 is defined as the length L of the base body 2. Furthermore, the direction of the thickness T is referred to as the thickness direction DT, the direction of the width W is referred to as the width direction DW, and the direction of the length L is referred to as the length direction DL.

[0014] Hereinafter, the surface along the length direction DL and the thickness direction DT (the surface perpendicular to the width direction DW) will be referred to as the LT surface, the surface along the thickness direction DT and the width direction DW (the surface perpendicular to the length direction DL) will be referred to as the WT surface, and the surface along the length direction DL and the width direction DW (the surface perpendicular to the thickness direction DT) will be referred to as the LW surface. Furthermore, the cross-sections of the inductor 1 along the LT surface, WT surface, and LW surface will be referred to as the LT cross-section, WT cross-section, and LW cross-section, respectively.

[0015] In this embodiment, the base body 2 comprises a coil conductor (coil) 20 and a substantially rectangular parallelepiped-shaped magnetic core (magnetic material, core portion) 30 in which the coil conductor 20 is embedded. The base body 2 of this embodiment is configured as a molded inductor in which the coil conductor 20 is sealed in the magnetic core 30.

[0016] The magnetic core 30 is a molded body formed by compressing a mixed powder of magnetic particles and resin into a roughly hexahedral shape by pressurizing and heating it while enclosing the coil conductor 20. During this process, both ends of the coil conductor 20 are exposed on the bottom surface 10 side. The ends of the coil conductor 20 form two external electrode portions (not shown).

[0017] The magnetic particles contained in the mixed powder of this embodiment are made of a soft magnetic material. The magnetic particles are particles having metal particles, an oxide film covering the surface of the metal particles, and an insulating film covering the surface of the oxide film. The insulation resistance and dielectric strength are increased by covering the metal particles with the oxide film and the insulating film. The magnetic particles may have only one particle size, or they may have two or more particle sizes with different particle sizes, and each magnetic particle may be different. In the magnetic particles of this embodiment, amorphous iron powder or crystalline atomized iron powder is used for the larger particle size metal particles, and carbonyl iron powder is used for the smaller particle size metal particles. Furthermore, nanocrystalline materials may be used to further reduce losses. The insulating film for the larger particle size metal particles is phosphate glass formed by a mechanochemical method, and the insulating film for the smaller particle size metal particles is iron oxide formed by surface oxidation, or formed by a sol-gel method.

[0018] The resin contained in the mixed powder of this embodiment includes multiple types of resin materials. For example, the resin materials contained in the mixed powder of this embodiment include 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. In addition to epoxy resin, thermosetting resins such as phenolic resin, polyester resin, polyimide resin, and polyolefin resin may be used as the resin materials contained in the mixed powder.

[0019] Inductor 1 with this configuration is used as an electronic component in electrical circuits where large currents flow, as well as as a choke coil in DC-DC converter circuits and power supply circuits. Inductor 1 is also used 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.

[0020] [Detailed Configuration of the Inductor] Figure 2 is a perspective plan view showing the internal configuration of the inductor 1 according to the first embodiment. The conductor 21 constituting the coil conductor 20 is composed of a conductor and a coating layer formed on the surface of the conductor. The conductor 21 in this embodiment is a flat wire with a rectangular cross-section. By using a flat wire, it becomes easy to wind the conductor 21 without gaps. The conductor of the conductor 21 is a conductor with a rectangular cross-section. The coating layer of the conductor 21 is composed of an insulating layer formed on the surface of the conductor and a fusion layer formed on the surface of the insulating layer.

[0021] The coil conductor 20 has a winding portion 20a formed by winding a conductor 21, and a lead portion 20b drawn out from the winding portion 20a is brought out onto the surface of the base body 2. The coil conductor 20 in this embodiment is α-wound. α-wound refers to a state in which the coil conductor 20 is wound in a spiral shape in two stages such that the lead portions 20b at the beginning and end of the winding are located on the outer circumference.

[0022] In this embodiment, the coil conductor 20, which is an α-winding coil, is wound spirally around a predetermined winding shaft K such that both ends are located on the outer circumference and are connected to each other on the inner circumference. That is, the coil conductor 20 comprises a winding portion 20a wound around the winding shaft K, a pair of lead portions 20b drawn out from the winding portion 20a, and a pair of external electrode connection portions 20c provided at the tips of the lead portions 20b. The winding shaft K is set according to the core portion of the columnar portion 31b of the T-shaped core portion 31.

[0023] The winding portion 20a is wound in two stages, upper and lower, along the winding shaft K. The lead portion 20b is pulled out from the winding portion 20a. The lead portion 20b is formed at the tip of the lead portion 20b by forming the tip into an S-shape. The side of the external electrode connection portion 20c on the bottom surface 10 of the base body 2, perpendicular to the wide surface of the conductor 21, is exposed to the outside from the bottom surface 10 of the magnetic core 30. An external electrode portion is formed on the bottom surface 10 of the base body 2, and the exposed portion of the external electrode connection portion 20c is connected to the external electrode portion. The external electrode portion is electrically connected to the wiring of a circuit board (not shown) by appropriate mounting means such as soldering.

[0024] Figure 3 is a schematic diagram corresponding to the cross-section along line III-III in Figure 2. In Figure 3, the winding portion 20a of the coil conductor 20 is shown in a simplified rectangular shape. The magnetic core 30 has a T-shaped core portion (first core portion) 31 that is T-shaped in cross-section, and a U-shaped core portion (second core portion) 32 that is U-shaped in cross-section. The U-shaped core portion 32 is arranged to cover the T-shaped core portion 31. The coil conductor 20 is housed between the U-shaped core portion 32 and the T-shaped core portion 31. The metallic magnetic powder of the T-shaped core portion 31 is Fe-Si based metallic magnetic powder. The average particle size of the metallic magnetic powder of the T-shaped core portion 31 is 4 μm or more and 20 μm or less. The metallic magnetic powder of the U-shaped core portion 32 is Fe-Si based metallic magnetic powder. The average particle size of the metallic magnetic powder of the U-shaped core portion 32 is 4 μm or more and 20 μm or less. The filling rate of the metal magnetic powder in the T-shaped core portion 31 is greater than that of the metal magnetic powder in the U-shaped core portion 32.

[0025] The T-shaped core portion 31 has a flat plate-like portion 31a and a columnar portion 31b that protrudes in the thickness direction from the center of the plate-like portion 31a. The bottom surface of the plate-like portion 31a constitutes the bottom surface 10 of the base body 2.

[0026] In this embodiment, the plate-like portion 31a is rectangular in shape. The plate-like portion 31a supports the surface of the winding portion 20a of the coil conductor 20 in the thickness direction DT. At least a portion of the side surface of the plate-like portion 31a is located closer to the winding shaft K than the winding portion 20a. In this embodiment, both side surfaces of the plate-like portion 31a in the width direction DW are located inward of the winding portion 20a. In other words, at least a portion of the side surface of the winding portion 20a protrudes beyond the side surface of the plate-like portion 31a. In this embodiment, both side surfaces of the winding portion 20a in the width direction DW protrude outward from the side surface of the plate-like portion 31a.

[0027] The columnar portion 31b extends into the inner circumference of the winding portion 20a. In this embodiment, the columnar portion 31b penetrates the winding portion 20a and protrudes beyond the winding portion 20a in the thickness direction DT. However, the columnar portion 31b does not necessarily have to protrude beyond the winding portion 20a. That is, the columnar portion 31b may be the same size as the winding portion 20a in the thickness direction. In plan view, the columnar portion 31b is formed in an oval shape where the length direction DL is longer than the width direction DW (see Figure 2).

[0028] The U-shaped core portion 32 has a plate-shaped base portion 32a, an outer peripheral wall portion 32b extending from the outer peripheral end of the base portion 32a in the winding axis direction K, and a winding portion 32c extending from the tip of the outer peripheral wall portion 32b so as to wrap around the surface of the coil conductor 20 in the thickness direction DT. In this embodiment, the base portion 32a is rectangular. In the thickness direction DT, the base portion 32a has an uneven shape corresponding to the unevenness of the columnar portion 31b of the T-shaped core portion 31 and the coil conductor 20.

[0029] The outer peripheral wall portion 32b has a total of four wall portions corresponding to the rectangular shape of the base portion 32a: a pair of wall portions DL in the length direction (proximity outer peripheral surfaces) 33 and a pair of wall portions DW in the width direction (non-proximity outer peripheral surfaces) 34. In other words, of the outer peripheral wall portion 32b, in a plan view, the portion facing the side surface of the T-shaped core portion 31 that intersects with the lead portion 20b is the wall portion (proximity outer peripheral surface) 33, and the portion facing the side surface of the T-shaped core portion 31 that does not intersect with the lead portion 20b is the wall portion (non-proximity outer peripheral surface) 34.

[0030] In this embodiment, in the inductor 1, in the WT cross-section, the outer peripheral end (outer peripheral surface) 31b1 of the columnar portion 31b of the T-shaped core portion 31, the inner peripheral end 20a1 of the winding portion 20a of the coil conductor 20, the outer peripheral end 31a1 of the plate-shaped portion 31a of the T-shaped core portion 31, the outer peripheral end (outer peripheral surface) 20a2 of the winding portion 20a of the coil conductor 20, and the side surface 16 as the outer peripheral end of the base body 2 are located in that order in the direction away from the winding shaft K.

[0031] In other words, in the inductor 1, the T-shaped core portion 31 and the U-shaped core portion 32 can be positioned via the coil conductor 20 in the width direction DW of the base body 2, making it easier to adjust the thickness of the magnetic core 30 in the width direction DW of the base body 2 with respect to the winding shaft K.

[0032] [Overview of Inductor Manufacturing Process] Figure 4 is a schematic diagram of the manufacturing process of inductor 1 according to the first embodiment. As shown in the figure, the manufacturing process of inductor 1 includes a first pre-molded body preparation step ST1, a second pre-molded body preparation step ST2, a coil formation step ST3, a first pre-molded body placement step ST4, a base body formation step ST5, and the like.

[0033] The first preliminary molded body preparation step ST1 and the second preliminary molded body preparation step ST2 are steps to prepare the first preliminary molded body 131 and the second preliminary molded body 132, which are formed into an easy-to-handle solid by pressurizing the mixed powder, which is the material for the base body 2.

[0034] In the first pre-molded body preparation step ST1, a first pre-molded body 131 is formed by containing metal magnetic powder and resin and having a columnar portion 131b and a plate-shaped portion 131a. The first pre-molded body 131 corresponds to the portion that will become the T-shaped core portion 31 after molding.

[0035] In the second pre-molded body preparation step ST2, a second pre-molded body 132 is prepared, which contains metal magnetic powder and resin and has a recess 135 on its upper surface due to a wall 132b that protrudes upward from the plate-like portion 132a. Specifically, the second pre-molded body 132 is prepared in the molding die 100 with the recess 135 facing upward. By molding the second pre-molded body 132 using the molding die 100, it becomes unnecessary to remove the second pre-molded body 132 from the molding die 100. Therefore, it becomes unnecessary to set clearances and other settings required when attaching and detaching the second pre-molded body 132 from the mold. Also, because it can be held by the molding die 100, the thickness of the wall 132b in the second pre-molded body 132 can be made thinner while making the wall 132b less likely to collapse. At this time, the length DT in the thickness direction of the wall 132b, i.e., the height T1, is set to be 51% or more of the height T2 of the coil conductor 20.

[0036] In the coil formation process ST3, a coil conductor 20 is provided on the first pre-molded body 131. Specifically, a coil conductor 20 is formed having a wound portion 20a that is wound around the columnar portion 131b of the first pre-molded body 131 and protrudes outward from the outer peripheral end 131a1 of the plate-shaped portion 131a of the first pre-molded body 131. Specifically, the coil formation process ST3 forms the coil conductor 20 from a flat rectangular wire made of copper as the conductor 21. In this embodiment, the conductor 21 is directly wound around the columnar portion 131b of the first pre-molded body 131. In the coil formation process ST3, the coil conductor 20 is formed in a shape having the aforementioned wound portion 20a and lead portion 20b by winding the conductor using a winding method called "α winding".

[0037] The number of turns in the winding portion 20a is not particularly limited, but is determined so as to achieve the desired inductance. However, the winding portion 20a is wound so as to protrude outward from the outer peripheral wall of the plate-shaped portion 131a of the first pre-molded body 131. In this embodiment, the winding portion 20a is wound so as to protrude outward from the outer peripheral ends 131a1, which are both sides in the width direction DW of the plate-shaped portion 131a of the first pre-molded body 131. The lead portion 20b is formed at the tip into an S-shape to form an external electrode connection portion 20c. The external electrode connection portion 20c is used to crimp the coil conductor 20 to the first pre-molded body 131.

[0038] Figure 5 is a perspective view showing the state in which the first pre-molded body 131 is positioned such that the coil conductor 20 of the first pre-molded body 131 is housed in the recess 135 of the second pre-molded body 132. Figure 6 is a plan view showing the state in Figure 5. Figure 7 is a cross-sectional view showing the inside of the molding dies 100 and 101 corresponding to the cross-section along line VII-VII in Figure 6. In the first pre-molded body positioning step ST4, the first pre-molded body 131 is positioned on the second pre-molded body 132 such that the winding portion 20a of the coil conductor 20 provided on the first pre-molded body 131 is housed in the recess 135 of the second pre-molded body 132. At this time, the first pre-molded body 131 with the coil conductor 20 attached is housed in the recess 135 with its columnar portion 131b facing downwards.

[0039] At this time, the first pre-molded body 131 may be placed in the second pre-molded body 132 while housed in the molding die 101 (see Figure 7). The first pre-molded body 131 is placed in the molding dies 100, 101 such that, in a cross section corresponding to the WT cross section, the distance λ11 between the outer peripheral end 131a1 of the plate-like portion 131a and the inner peripheral surfaces 100a, 101a of the molding dies 100, 101 is greater than the distance λ12 between the outer peripheral end 20a2 of the winding portion 20a of the coil conductor 20 and the inner peripheral surfaces 100a, 101a of the molding dies 100, 101.

[0040] In this embodiment, when the winding portion 20a is α-wound, the thickness of the winding portion 20a in the width direction of the base body 2 varies depending on the number of turns, and in the winding portion 20a, only one outer circumference with respect to the center of the winding shaft K is shifted outward by the width of one conductor 21. In this embodiment, it is possible to eccentricate the winding shaft K, which is the core of the T-shaped core portion 31, from the center O of the base body 2 after molding. Therefore, it is possible to place the first pre-molded body 131 in the mold without having to prepare multiple molds for each α-winding method of the winding portion 20a. At this time, by bringing the portion of the winding portion 20a of the coil conductor 20 that protrudes from the plate-shaped portion 131a into contact with the inner surface of the wall 132b that forms the recess 135, it is possible to position the coil conductor 20 with respect to the second pre-molded body 132.

[0041] Here, as shown in Figure 7, the wall 132b of the recess 135 of the second pre-molded body 132 has a length DT in the thickness direction, i.e., a height T1 that is 51% or more of the height T2 of the coil conductor 20. This allows the wall 132b to contact and position either of the two layers of wire 21, even when the wire 21 is stacked in two layers, such as in an α-winding configuration. Therefore, it is easier to prevent the position of the coil conductor 20 from shifting when the molding die 100 is heated and pressurized, and the coil conductor 20 is prevented from being molded with the outside of the base body 2 exposed.

[0042] In the base body formation process ST5, the first pre-molded body 131, the coil conductor 20, and the second pre-molded body 132, which are set in the molding dies 100 and 101, are heated and pressed in the direction in which the first pre-molded body 131 and the second pre-molded body 132 overlap, thereby hardening them. During this process, a part of the second pre-molded body 132 may collapse, filling the gaps between the first pre-molded body 131 and the second pre-molded body 132 as they harden. As a result, a base body 2 with the coil conductor 20 enclosed in the magnetic core 30 is formed.

[0043] After the base body formation process ST5, predetermined base body polishing processes and plating layer formation processes are carried out. This completes the manufacture of the inductor 1.

[0044] As explained above, the inductor 1 according to the first embodiment is an inductor 1 comprising an element body 2 having a magnetic core 30 containing metal magnetic powder and a resin, and a coil conductor 20 embedded inside the magnetic core 30. In this inductor 1, the magnetic core 30 has a T-shaped core portion 31 having a columnar portion 31b and a plate-shaped portion 31a, and a U-shaped core portion 32 covering the T-shaped core portion 31. The coil conductor 20 has a wound portion 20a formed by winding a conducting wire 21, and a pair of lead portions 20b drawn from the wound portion 20a to an outer peripheral side relative to the wound portion 20a, and at least a part of the wound portion 20a protrudes to the outer peripheral side beyond the outer peripheral end 31a1 of the plate-shaped portion 31a. The U-shaped core portion 32 has a wall portion 33 which is an outer peripheral end where the lead portions 20b of the coil conductor 20 are adjacent, and a wall portion 34 which is an outer peripheral end of a portion different from the wall portion 33. The U-shaped core portion 32 is formed such that a distance λ1 between the wall portion 34 and the outer peripheral end 31a1 of the T-shaped core portion 31 is larger than a distance λ2 between the wall portion 34 and the outer peripheral end 20a2 of the wound portion 20a of the coil conductor 20. According to this configuration, the inductor 1 can be provided in which the positions of the T-shaped core portion 31 and the U-shaped core portion 32 are defined with reference to the outer peripheral end 20a2 of the wound portion 20a of the coil conductor 20. Therefore, it is possible to provide the inductor 1 in which the wall thickness of the magnetic core 30 between the outer peripheral end 20a2 of the coil conductor 20 and the outer surface 16 of the element body 2 can be easily adjusted.

[0045] In the present embodiment, in the wound portion 20a, the portion facing the wall portion 33 does not protrude to the outer peripheral side beyond the outer peripheral end of the plate-shaped portion 31a, and the portion facing the wall portion 34 protrudes to the outer peripheral side beyond the outer peripheral end 31a1 of the plate-shaped portion 31a. According to this configuration, the coil conductor 20 can be easily positioned on the T-shaped core portion 31 by using the lead portions 20b of the coil conductor 20.

[0046] Furthermore, in the present embodiment, the conductive wire 21 is a rectangular flat conductive wire, and the winding portion 20a is formed by alpha winding. According to this configuration, when the winding portion 20a of the coil conductor 20 is formed by alpha winding, variation in thickness occurs in the radial direction of the winding portion 20a depending on the number of turns, and the conductive wire 21 is shifted by one wire toward the outer peripheral side only on one side with respect to the center of the winding axis K. However, since the positions of the T-shaped core portion 31 and the U-shaped core portion 32 are defined with reference to the outer peripheral end 20a2 of the winding portion 20a of the coil conductor 20, it is possible to obtain the inductor 1 in which the positions of the T-shaped core portion 31 and the U-shaped core portion 32 are defined in a state where the shift is easily absorbed.

[0047] Furthermore, in the present embodiment, the filling rate of metallic magnetic powder in the T-shaped core portion 31 is higher than the filling rate of metallic magnetic powder in the U-shaped core portion 32. According to this configuration, by making the filling rate of metallic magnetic powder in the T-shaped core portion 31 higher than that in the U-shaped core portion 32, the characteristics of the magnetic core 30 can be adjusted more easily than when the filling rates of metallic magnetic powder in the T-shaped core portion 31 and the U-shaped core portion 32 are the same. Furthermore, the boundary between the T-shaped core portion 31 and the U-shaped core portion 32 can be easily distinguished.

[0048] Furthermore, in the present embodiment, the pair of lead portions 20b are led out to the bottom surface (mounting surface) 10 of the element body 2. According to this configuration, external electrodes can be easily provided.

[0049] Furthermore, in the present embodiment, in the U-shaped core portion 32, on the bottom surface (mounting surface) 10 side of the element body 2, a winding portion 32c is formed as a portion where the distance λ1 between the wall portion 34 and the outer peripheral end 31a1 of the T-shaped core portion 31 is larger than the distance λ2 between the wall portion 34 and the outer peripheral end 20a2 of the winding portion 20a of the coil conductor 20. According to this configuration, even if the size of the plate-like portion 31a of the T-shaped core portion 31 is small, the magnetic core 30 can be formed around the plate-like portion 31a of the T-shaped core portion 31 by forming the U-shaped core portion 32 to enclose the coil conductor 20.

[0050] Furthermore, in this embodiment, the outer peripheral end 31b1 (see Figure 3) of the T-shaped core portion 31 on the upper surface 12 side of the base body 2 is smaller than the outer peripheral end 31a1 on the bottom surface 10 side of the base body 2. That is, the outer peripheral end 31b1 of the columnar portion 31b is smaller than the outer peripheral end 31a1 of the plate-shaped portion 31a. In this case, the U-shaped core portion 32 also has a portion where the distance λ3 (see Figure 3) between the wall portion 34 and the outer peripheral end 31b1 of the T-shaped core portion 31 is larger than the distance λ2 between the wall portion 34 and the outer peripheral end 20a2 of the winding portion 20a of the coil conductor 20. With this configuration, even if the size of the columnar portion 31b of the T-shaped core portion 31 is small, the U-shaped core portion 32 is formed to fill the area around the coil conductor 20, and a magnetic core 30 can be formed around the columnar portion 31b of the T-shaped core portion 31.

[0051] As described above, the method for manufacturing the inductor 1 of the first embodiment is a method for manufacturing an inductor comprising a base body 2 having a magnetic core 30 containing metal magnetic powder and resin, and a coil conductor 20 embedded inside the magnetic core 30. This method for manufacturing an inductor comprises a first pre-molded body preparation step ST1 for preparing a first pre-molded body 131 containing metal magnetic powder and resin and having a columnar portion 131b and a plate-shaped portion 131a; a second pre-molded body preparation step ST2 for preparing a second pre-molded body 132 having a recess 135 on its upper surface due to an upwardly protruding wall 132b, in a molding die 100 with the recess 135 facing upward; and a winding portion 20a wound around the columnar portion 131b of the first pre-molded body 131, which protrudes outward from the outer peripheral end 131a1 of the plate-shaped portion 131a of the first pre-molded body 131. The process includes a coil forming step ST3 for forming a coil conductor 20 having a winding portion 20a, a first pre-molded body placement step ST4 for positioning the first pre-molded body 131 so that the winding portion 20a of the coil conductor 20 provided on the first pre-molded body 131 is accommodated in the recess 135 of the second pre-molded body 132, and a base body forming step ST5 for thermally compressing the first pre-molded body 131 and the second pre-molded body 132 in molding dies 100 and 101 to form a base body 2 having a T-shaped core portion 31 having a columnar portion 31b and a plate-shaped portion 31a, and a U-shaped core portion 32 covering the T-shaped core portion 31. With this configuration, the second pre-molded body 132 can be held by the molding die 100, so the necessary wall 132b can be reliably formed on the outer circumference of the coil conductor 20 before molding. Therefore, it is possible to provide an inductor 1 that allows for easy adjustment of the wall thickness of the magnetic core 30 between the outer peripheral end 20a2 of the coil conductor 20 and the side surface (outer surface) 16 of the base body 2.

[0052] In this embodiment, in the first pre-molded body placement step ST4, the winding portion 20a of the coil conductor 20 provided on the first pre-molded body 131 is brought into contact with the inner circumferential surface of the wall 132b of the recess 135 of the second pre-molded body 132 and housed there. With this configuration, by assembling based on the outer circumferential end 20a2 of the winding portion 20a of the coil conductor 20, it is easy to minimize the clearance required during assembly, and thus it is easy to maximize the winding portion 20a of the coil conductor 20. In particular, when the winding portion 20a is α-wound, it becomes possible to eccentrically position the core portion of the same magnetic core 30 shape from the center of the base body 2, eliminating the need for multiple molds for each winding method of the winding portion 20a.

[0053] Furthermore, in this embodiment, the second pre-molded body 132 is formed such that the height T1 of the wall 132b of the recess 135 is 51% or more of the height T2 of the winding portion 20a of the coil conductor 20. With this configuration, the coil conductor 20 can be positioned during molding, and it is easier to prevent the coil conductor 20 from being exposed from the magnetic core 30 during molding.

[0054] Furthermore, in this embodiment, the first pre-molded body 131 is positioned in the molding die 100 such that the distance λ11 between the outer peripheral end 131a1 of the plate-shaped portion 131a in the width direction DW of the base body 2 and the inner peripheral surface 100a of the molding die 100 is greater than the distance λ12 between the outer peripheral end 20a2 of the winding portion 20a of the coil conductor 20 and the inner peripheral surface 100a of the molding die 100. With this configuration, the second pre-molded body 132 can be held by the molding die 100, so that the necessary wall 132b can be reliably formed on the outer peripheral side of the coil conductor 20 before molding. Therefore, it is possible to provide an inductor 1 in which the wall thickness of the magnetic core 30 between the outer peripheral end 20a2 of the coil conductor 20 and the side surface (outer surface) 16 of the base body 2 can be easily adjusted.

[0055] Furthermore, in this embodiment, in the coil formation step ST3, a coil conductor 20 is formed on the first pre-molded body 131 by winding a conductor 21 around the columnar portion 131b of the first pre-molded body 131. With this configuration, a coil conductor 20 can be easily formed on the first pre-molded body 131.

[0056] [2. Second Embodiment] Next, a second embodiment will be described. Note that components similar to those in the first embodiment described above may be denoted by the same reference numerals and their descriptions may be omitted.

[0057] Figure 8 shows a part of the manufacturing method of the inductor 1 according to the second embodiment. Figure 8 corresponds to a part of the process in Figure 4. The manufacturing method of the inductor in the second embodiment differs from the first embodiment in that it includes a coil formation step ST203 instead of the coil formation step ST3 of the first embodiment. That is, in the coil formation step ST203 of the second embodiment, a coil conductor 220 with a pre-formed winding portion 20a is formed. Then, this air-core wound coil conductor 220 having the winding portion 20a is inserted and mounted into the columnar portion 131b of the first pre-molded body 131. This is different from the first embodiment.

[0058] Therefore, in the second embodiment as well, it is possible to provide an inductor 1 in which the wall thickness of the magnetic core 30 between the outer peripheral end 20a2 of the coil conductor 220 and the side surface 16 which is the outer surface of the base body 2 can be easily adjusted.

[0059] In particular, in this embodiment, in the coil formation step ST203, the coil conductor 220 is formed in the first pre-molded body 131 by inserting the air-core wound coil conductor 220 into the columnar portion 131b of the first pre-molded body 131. With this configuration, the coil conductor 220 can be easily formed in the first pre-molded body 131.

[0060] [3. Third Embodiment] Figure 9 is a schematic diagram of the manufacturing process of the inductor 1 according to the third embodiment. As shown in the figure, the manufacturing process of the inductor 1 includes a first pre-molded body preparation step ST1, a second pre-molded body preparation step (second pre-molded body formation step) ST2, a coil formation step (coil mounting step) ST3, a first pre-molded body placement step (first pre-molded body mold housing step) ST4, a base body formation step ST5, and the like.

[0061] The first preliminary molded body preparation step ST1 and the second preliminary molded body preparation step ST2 are steps to prepare the first preliminary molded body 131 and the second preliminary molded body 132, which are formed into an easy-to-handle solid by pressurizing the mixed powder, which is the material for the base body 2.

[0062] In the first pre-molded body preparation step ST1, a first pre-molded body 131 is formed by containing metal magnetic powder and resin and having a columnar portion 131b and a plate-shaped portion 131a. The first pre-molded body 131 corresponds to the portion that will become the T-shaped core portion 31 after molding.

[0063] In the second pre-molded body preparation step ST2, a second pre-molded body 132 is prepared, which contains metal magnetic powder and resin and has a recess 135 on its upper surface due to a wall (surrounding wall) 132b that protrudes upward from the bottom surface (plate-like portion) 132a. Specifically, the second pre-molded body 132 is prepared in the molding die 100 with the recess 135 facing upward. By molding the second pre-molded body 132 using the molding die 100, it becomes unnecessary to remove the second pre-molded body 132 from the molding die 100. Therefore, it becomes unnecessary to set clearances and other settings required when attaching and detaching the second pre-molded body 132 from the mold. Also, because it can be held by the molding die 100, the wall 132b is less likely to collapse, and the thickness of the wall 132b in the second pre-molded body 132 can be made thinner. In this case, the length of the wall 132b in the thickness direction DT, i.e., the height T1, is set to be 51% or more of the height T2 of the coil conductor 20.

[0064] In the coil formation process ST3, a coil conductor 20 is provided on the first pre-molded body 131. Specifically, a coil conductor 20 is formed having a wound portion 20a that is wound around the columnar portion 131b of the first pre-molded body 131 and protrudes outward from the outer peripheral end 131a1 of the plate-shaped portion 131a of the first pre-molded body 131. Specifically, the coil formation process ST3 forms the coil conductor 20 from a flat rectangular wire made of copper as the conductor 21. In this embodiment, the conductor 21 is directly wound around the columnar portion 131b of the first pre-molded body 131. In the coil formation process ST3, the coil conductor 20 is formed in a shape having the aforementioned wound portion 20a and lead portion 20b by winding the conductor using a winding method called "α winding".

[0065] The number of turns in the winding portion 20a is not particularly limited, but is determined so as to achieve the desired inductance. However, the winding portion 20a is wound so as to protrude outward from the outer peripheral wall of the plate-shaped portion 131a of the first pre-molded body 131. In this embodiment, the winding portion 20a is wound so as to protrude outward from the outer peripheral ends 131a1, which are both sides in the width direction DW of the plate-shaped portion 131a of the first pre-molded body 131. The lead portion 20b is formed at the tip into an S-shape to form an external electrode connection portion 20c. The external electrode connection portion 20c is used to crimp the coil conductor 20 to the first pre-molded body 131.

[0066] In the first pre-molded body placement step ST4, the first pre-molded body 131 is placed on the second pre-molded body 132 such that the winding portion 20a of the coil conductor 20 provided on the first pre-molded body 131 is accommodated in the recess 135 of the second pre-molded body 132. At this time, the first pre-molded body 131 with the coil conductor 20 attached is accommodated in the recess 135 with the columnar portion 131b facing downwards.

[0067] At this time, the first pre-molded body 131 may be placed in the second pre-molded body 132 while housed in the molding die 101. The first pre-molded body 131 is placed in the molding dies 100, 101 such that, in a cross section corresponding to the WT cross section, the distance λ11 between the outer peripheral end 131a1 of the plate-like portion 131a and the inner peripheral surfaces 100a, 101a of the molding dies 100, 101 is greater than the distance λ12 between the outer peripheral end 20a2 of the winding portion 20a of the coil conductor 20 and the inner peripheral surfaces 100a, 101a of the molding dies 100, 101.

[0068] In this embodiment, when the winding portion 20a is α-wound, the thickness of the winding portion 20a in the width direction of the base body 2 varies depending on the number of turns, and in the winding portion 20a, only one outer circumference with respect to the center of the winding shaft K is shifted outward by the width of one conductor 21. In this embodiment, it is possible to eccentricate the winding shaft K, which is the core of the T-shaped core portion 31, from the center O of the base body 2 after molding. Therefore, it is possible to place the first pre-molded body 131 in the mold without having to prepare multiple molds for each α-winding method of the winding portion 20a. At this time, by bringing the portion of the winding portion 20a of the coil conductor 20 that protrudes from the plate-shaped portion 131a into contact with the inner surface of the wall 132b that forms the recess 135, it is possible to position the coil conductor 20 with respect to the second pre-molded body 132.

[0069] Here, the wall 132b of the recess 135 of the second pre-molded body 132 has a length DT in the thickness direction, i.e., a height T1 that is 51% or more of the height T2 of the coil conductor 20. This allows the wall 132b to contact and position either of the two layers of wire 21, even when the wire 21 is stacked in two layers, such as in an α-winding configuration. Thus, it is easier to prevent the position of the coil conductor 20 from shifting when the molding die 100 is heated and pressurized, and it is prevented that the coil conductor 20 is molded with its position exposed to the outside of the base body 2.

[0070] In the base body formation process ST5, the first pre-molded body 131, the coil conductor 20, and the second pre-molded body 132, which are set in the molding dies 100 and 101, are heated and pressed in the direction in which the first pre-molded body 131 and the second pre-molded body 132 overlap, thereby hardening them. During this process, a part of the second pre-molded body 132 may collapse, filling the gaps between the first pre-molded body 131 and the second pre-molded body 132 as they harden. As a result, a base body 2 with the coil conductor 20 enclosed in the magnetic core 30 is formed.

[0071] After the base body formation process ST5, predetermined base body polishing processes and plating layer formation processes are carried out. This completes the manufacture of the inductor 1.

[0072] [Details of the Inductor Manufacturing Process According to the Third Embodiment] Figure 10 is an explanatory diagram of the second pre-molded body preparation process ST2. Figure 11 is a longitudinal cross-sectional view of Figure 10. Specifically, Figure 11 shows a cross-section corresponding to the cross-section along line XI-XI in Figure 10. The outline of the second pre-molded body preparation process ST2 will be described in detail below. The second pre-molded body preparation process ST2 includes a start process ST21, a filling and heating process ST22, a pressurizing and cooling process ST23, and a finish process ST24. The start process ST21, the filling and heating process ST22, the pressurizing and cooling process ST23, and the finish process ST24 are performed in this order.

[0073] In the starting step ST21, the molding die 200 to be used in the second preliminary molded body preparation step ST2 is prepared. The molding die 200 is made of a material that can be heat-compressed. That is, the molding die 200 is used not only for powder compaction but also for heat-compression molding. As for the material of the molding die 200, for example, carbon tool steel, cold-work tool steel, hot-work tool steel, stainless steel, pre-hardened steel, etc. can be used.

[0074] The molding die 200 of this embodiment has a flat mold base portion 201. Multiple formation recesses 202 are formed in the mold base portion 201, recessed in the thickness direction. The formation recesses 202 are formed in a shape corresponding to the shape of the second pre-molded body 132 that will become the inductor 1. The formation recesses 202 of this embodiment are composed of a bottom wall 202a and an outer peripheral wall 202b formed on the outer periphery of the bottom wall 202a.

[0075] Multiple recessed areas 202 are formed in the mold base portion 201. Multiple recessed areas 202 are formed in the mold base portion 201 at intervals. Hereinafter, in the molding die 200, a portion having one recessed area 202 will simply be referred to as the molding die 100. That is, the molding die 200 has multiple molding dies 100.

[0076] In this embodiment, the molding die 200 is arranged along a horizontal plane. Therefore, the formation recess 202 is formed on the upper surface of the mold base portion 201 of the molding die 200.

[0077] In the filling and heating process ST22, each formation recess 202 is filled with a pre-molded body material 130 made of metal magnetic powder. Once the pre-molded body material 130 is filled into each formation recess 202, the molding die 200 is heated for a predetermined time by a heating device (not shown). This softens the pre-molded body material 130 in the formation recess 202.

[0078] In the pressurized cooling process ST23, a pressurized jig member 300 positioned opposite the molding die 200 is activated. The pressurized jig member 300 has a flat jig base portion 301 positioned opposite the mold base portion 201 of the molding die 200, and a rod-shaped jig 302 protruding from the jig base portion 301 toward the molding die 200. Multiple jigs 302 are provided according to the position of each formed recess 202. The material of the jig 302 can be the same as that of the molding die 200. Specifically, the material of the jig 302 can be, for example, carbon tool steel, cold work tool steel, hot work tool steel, stainless steel, pre-hardened steel, etc.

[0079] Figure 12 shows the size relationship between the formation recess 202 of the molding die 200 and the jig 302 of the pressurizing jig member 300. In this embodiment, the jig 302 has a rounded rectangular cross-section. A rounded rectangle is a shape in which the four corners of a rectangle are rounded to form R surfaces 136. The jig 302 tapers slightly towards its tip, i.e., as it approaches the molding die 200. The jig 302 has a side surface with an inclination angle θ0 with respect to the axis L0 of the jig 302. The inclination angle θ0 of the side surface is set according to the shape of the wall 132b of the second pre-molded body 132. A relief groove 302d is formed on the outer circumference of the tip of the jig 302.

[0080] Here, the molding die 100 of the molding die 200 is a rectangular mold having opening widths L1 and W1 in the longitudinal direction DL and the width direction DW. In the portion of the jig 302 that enters the formation recess 202, the length L2 of the jig 302 in the longitudinal direction DL passing through the center P1 is 65% to 98% of the opening width L1 of the formation recess 202 of the molding die 100 in the longitudinal direction DL passing through the center P1. Also, in the portion of the jig 302 that enters the formation recess 202, the length W2 of the jig 302 in the width direction DW passing through the center P1 is 65% to 98% of the opening width W1 of the formation recess 202 of the molding die 100 in the width direction DW passing through the center P1.

[0081] In the pressurized cooling process ST23, the pressurized jig member 300 is pushed toward the molding die 200 by a pressurizing device (not shown). As a result, each jig 302 of the pressurized jig member 300 is pushed into the formation recess 202 (see the dashed line in Figure 11). When inserting the jig 302 into the formation recess 202 of the molding die 100, the jig 302 is inserted without contacting the outer peripheral surface wall 202b of the formation recess 202 of the molding die 100.

[0082] Therefore, the pre-molded body material 130 is pushed toward the bottom wall 202a of the forming recess 202, and overflows out from the gap between the jig 302 and the bottom wall 202a of the forming recess 202, moving along the inner surface of the outer peripheral wall 202b of the forming recess 202. In other words, the pre-molded body material 130 takes on a shape corresponding to the gap shape between the jig 302 and the forming recess 202. Since the jig 302 does not come into contact with the outer peripheral wall 202b of the forming recess 202, it is easier to prevent the thin wall 132b of the second pre-molded body 132 from breaking, and it is easier to form the thin wall 132b of the second pre-molded body 132.

[0083] In this state, heating of the molding die 200 is terminated and the pre-molded body material 130 is cooled. This forms a second pre-molded body 132 with a recess 135 on its upper surface.

[0084] In the final step ST24, a pressurizing device (not shown) is activated to retract the pressurizing jig member 300 from the molding die 200. As a result, the second pre-molded body 132 is housed in each of the forming recesses 202 of the molding die 200. In this embodiment, since the jig 302 has a rounded rectangular cross-section, the shape of the recess 135 is formed as a rounded rectangle in plan view.

[0085] Here, because the jig 302 has a slightly tapered shape, the inner surface of the wall 132b of the second pre-molded body 132 is tapered. Therefore, the jig 302 is easier to remove from the second pre-molded body 132, and the wall 132b of the second pre-molded body 132 is less likely to conform to the jig 302 and collapse. Therefore, the wall 132b is easier to thin. In addition, the inner surface of the wall 132b is tapered at an inclination angle θ1 with respect to the direction of the normal La of the bottom surface 132a, due to the inclination angle θ0 of the jig 302. The inclination angle θ1 is greater than 0 degrees and 15 degrees or less.

[0086] In this way, the second pre-molded body preparation step ST2 prepares the second pre-molded body 132 within the formation recess 202 of the molding die 200. That is, the second pre-molded body preparation step ST2 prepares the second pre-molded body 132 within each molding die 100 of the molding die 200.

[0087] Therefore, after this, the first preliminary molded body placement process ST4, the base body formation process ST5, etc. are performed on each of the molding dies 100 of the molding die 200. In other words, in this embodiment, heating, pressurizing, and compression are performed on the molding die 200 in the base body formation process ST5, and the inductor 1 is manufactured.

[0088] As described above, the third embodiment of the inductor manufacturing method is a method for manufacturing an inductor comprising a base body 2 having a magnetic core 30 containing metal magnetic powder and resin, and a coil conductor 20 embedded inside the magnetic core 30. In this inductor manufacturing method, a first pre-molded body preparation step ST1 is performed to prepare a first pre-molded body 131 containing metal magnetic powder and resin, having a plate-shaped portion 131a and a columnar portion 131b formed on the plate-shaped portion 131a; a second pre-molded body preparation step ST2 is performed to fill a pre-molded body material 130 containing metal magnetic powder and resin into molding dies 100 and 200, soften the pre-molded body material 130 by heating, and then insert a jig 302 into the molding dies 100 and 200 to form a recess 135 on the surface of the softened pre-molded body material 130, thereby forming a second pre-molded body 132 having a recess 135 and a wall 132b provided around the recess 135; and the columnar portion 131b of the first pre-molded body 131 is used for winding the coil conductor 20. The process includes: a coil forming step ST3 in which the coil conductor 20 is attached so that it is inserted into part 20a; a first pre-molded body placement step ST4 in which the first pre-molded body 131 with the coil conductor 20 attached is housed in a molding die 100, 200 so that the outer peripheral end 20a2 of the winding portion 20a of the coil conductor 20 is close to the inner peripheral surface of the wall 132b of the second pre-molded body 132; and a base body forming step ST5 in which the first pre-molded body 131 and the second pre-molded body 132 are heat-compressed in the molding die 100, 200 to form a base body 2 having a magnetic core 30 having a T-shaped core portion 31 having a plate-shaped portion 31a and a columnar portion 31b formed on the plate-shaped portion 31a, a U-shaped core portion 32 covering the T-shaped core portion 31, and a coil conductor 20 embedded inside the magnetic core 30.

[0089] With this configuration, the coil conductor 20 is attached to the first pre-molded body 131 which has a stable shape, and the coil conductor 20 is placed in the recess 135 of the second pre-molded body 132. Compared to the case where magnetic powder is filled, the movement behavior of the magnetic powder that is placed around the coil conductor 20 can be stabilized. Therefore, with this configuration, it is possible to provide an inductor 1 in which the position of the coil conductor 20 can be set with precision, and the wall thickness of the magnetic core 30 between the outer peripheral end 20a2 of the coil conductor 20 and the side surface 16 which is the outer surface of the base body 2 can be easily adjusted.

[0090] Furthermore, in this embodiment, in the first pre-molded body placement step ST4, the first pre-molded body 131 to which the coil conductor 20 is attached is housed in the molding dies 100 and 200 such that the outer peripheral end 20a2 of the winding portion 20a of the coil conductor 20 contacts the inner peripheral surface of the wall 132b of the second pre-molded body 132. With this configuration, since the outer peripheral end 20a2 of the winding portion 20a of the coil conductor 20 contacts the inner peripheral surface of the wall 132b of the second pre-molded body 132, the position of the coil conductor 20 can be set with greater precision.

[0091] In this embodiment, in the first pre-molded body arrangement step ST4, a coil conductor 20 having a wound portion 20a in which at least a portion of the outer peripheral end (outer peripheral portion) 20a2 protrudes outward from the outer peripheral end (outer peripheral surface) 31a1 of the plate-shaped portion 131a of the first pre-molded body 131 is attached to the first pre-molded body 131 by winding a conductor 21 around the columnar portion 131b of the first pre-molded body 131. With this configuration, a coil conductor 20 having a wound portion 20a in which at least a portion of the outer peripheral end 20a2 protrudes outward from the outer peripheral end 31a1 of the plate-shaped portion 131a of the first pre-molded body 131 is easily attached to the first pre-molded body 131.

[0092] Furthermore, in this embodiment, a tapered surface is formed on the inner circumferential surface of the wall 132b of the second pre-molded body 132, such that the inclination angle θ1 with respect to the normal La of the bottom surface 132a of the second pre-molded body 132 is 15° or less. With this configuration, the jig 302 can be easily removed from the second pre-molded body 132, so even if the wall 132b is thinned before hardening, it is less likely to collapse when the jig 302 is removed, and the wall 132b can be made thinner more easily.

[0093] Furthermore, in this embodiment, the molding die 100 is a rectangular mold having opening widths L1 and W1 in mutually orthogonal longitudinal directions (first direction) DL and width directions (second direction) DW. The length L2 of the jig 302 in the longitudinal direction DL passing through the center P1 of the jig 302 is 65% to 98% of the opening width L1 of the molding die 100 in the longitudinal direction DL passing through the center P1. The length W2 of the jig 302 in the width direction DW passing through the center P1 of the jig 302 is 65% to 98% of the opening width W1 of the width direction DW passing through the center P1 of the molding die 100. When inserting the jig 302 into the forming recess 202 of the molding die 100, the jig 302 is inserted without contacting the outer peripheral surface wall (inner wall) 202b of the forming recess 202 of the molding die 100. This configuration makes it easier to prevent the thin wall 132b of the second pre-molded body 132 from breaking, and makes it easier to form the thin wall 132b of the second pre-molded body 132.

[0094] Furthermore, in this embodiment, the shape of the recess 135 of the second pre-molded body 132 is a rounded rectangle. With this configuration, the shape of the recess 135 of the second pre-molded body 132 can be made into the corners of a rectangle, and further, rounded surfaces 136 can be provided at the corners of the rectangle.

[0095] Furthermore, in this embodiment, the lead portion (lead) 20b of the coil conductor 20 is extended to the bottom surface (mounting surface) 10 of the base body 2. With this configuration, by forming the lead portion 20b to extend to the bottom surface 10 of the base body 2, the coil conductor 20 can be positioned relative to the first pre-molded body 131 by the lead portion 20b.

[0096] [4. Fourth Embodiment] Next, a fourth embodiment will be described. Note that components similar to those in the third embodiment described above may be denoted by the same reference numerals and their descriptions may be omitted.

[0097] Figure 13 shows a part of the manufacturing method of the inductor 1 according to the fourth embodiment. Figure 13 corresponds to a part of the process in Figure 9. The manufacturing method of the inductor of the fourth embodiment differs from the third embodiment in that it includes a coil formation step ST203 instead of the coil formation step ST3 of the third embodiment. That is, in the coil formation step ST203 of the fourth embodiment, a coil conductor 220 with a pre-formed winding portion 20a is formed. Then, this air-core wound coil conductor 220 having the winding portion 20a is inserted and mounted into the columnar portion 131b of the first pre-molded body 131. This is different from the third embodiment.

[0098] Therefore, in the fourth embodiment as well, it is possible to provide an inductor 1 in which the wall thickness of the magnetic core 30 between the outer peripheral end 20a2 of the coil conductor 220 and the side surface 16 which is the outer surface of the base body 2 can be easily adjusted.

[0099] In particular, in this embodiment, in the coil formation step ST203, the coil conductor 220 is formed on the first pre-molded body 131 by inserting the air-core wound coil conductor 220 into the columnar portion 131b of the first pre-molded body 131. That is, in this embodiment, in the coil formation step ST203, the coil conductor 20 having a wound portion 20a in which at least a part of the outer peripheral end 20a2 protrudes outward from the outer peripheral end 31a1 of the plate-shaped portion 131a of the first pre-molded body 131 is attached to the first pre-molded body 131 by attaching the winding portion 20a of the coil conductor 20 to the columnar portion 131b of the first pre-molded body 131. With this configuration, the coil conductor 20 having a wound portion 20a in which at least a part of the outer peripheral end 20a2 protrudes outward from the outer peripheral end 31a1 of the plate-shaped portion 131a of the first pre-molded body 131 can be easily attached to the first pre-molded body 131.

[0100] [5. Other Embodiments] In the embodiments described above, a configuration was described in which both sides of the winding portion 20a in the width direction DW protrude beyond the plate-shaped portion 31a, but the invention is not limited to this. For example, a configuration in which only one side of the winding portion 20a in the width direction DW protrudes beyond the plate-shaped portion 31a is also possible. Furthermore, a configuration in which any part of the winding portion 20a protrudes beyond the plate-shaped portion 31a is also possible.

[0101] In the embodiments described above, the coil conductors 20 and 220 are exemplified as having an α-winding configuration, but instead of α-winding, edgewise winding may be used. In this case, the lead portions 20b of the coil conductors 20 and 220 are drawn out from the winding portion 20a to the end face 14 of the base body 2.

[0102] In the embodiments described above, a configuration was described in which a wire 21 with a rectangular cross-section is used for the coil conductors 20 and 220. However, the coil conductors 20 and 220 may also be formed using a wire with a circular cross-section.

[0103] In the above-described embodiment, the lead portions 20b of the coil conductors 20 and 220 were shown to be led out toward the bottom surface 10 of the base body 2. However, the lead portions 20b may also be exposed on the side surface 16 adjacent to the bottom surface 10, or on the end surface 14 of the base body 2.

[0104] In the embodiments described above, a manufacturing method for manufacturing the inductor 1 was described in the order of first pre-molded body preparation step ST1, second pre-molded body preparation step ST2, and coil formation step ST3. However, the execution order of the first pre-molded body preparation step ST1, second pre-molded body preparation step ST2, and coil formation step ST3 is not limited to these. For example, the second pre-molded body preparation step ST2 may be executed before the first pre-molded body preparation step ST1 or the coil formation step ST3. Also, for example, the second pre-molded body preparation step ST2 may be executed after the first pre-molded body preparation step ST1 or the coil formation step ST3.

[0105] Figure 14 shows another embodiment. In the third embodiment described above, when manufacturing the inductor 1, a jig 302 with a rounded rectangular cross-section was used to form a rounded rectangular recess 135 in the second pre-molded body 132, but the embodiment is not limited to this. For example, a jig 302a with a circular cross-section may be used to form a circular recess 315a in the second pre-molded body 312a. Alternatively, for example, a jig 302b with an elliptical cross-section may be used to form an elliptical recess 315b in the second pre-molded body 312b. Furthermore, for example, a jig 302c with a polygonal cross-section may be used to form a polygonal recess 315c in the second pre-molded body 312c. In this case, a chamfered surface 316c may be formed at the corners of the polygonal recess 315c. These features allow the recesses 315a to 315c in the second pre-molded bodies 312a to 312c to be circular, elliptical, polygonal, or even have chamfered surfaces 316c at the corners of the polygonal shape.

[0106] All embodiments described above illustrate one aspect of the present invention and can be arbitrarily modified and applied without departing from the spirit of the invention. Furthermore, 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).

[0107] 1...Inductor, 2...Base, 10...Bottom surface (mounting surface), 12...Top surface, 14...End surface, 16...Side surface (outer surface), 20...Coil conductor (coil), 20a...Winding section, 20a1...Inner circumference end, 20a2...Outer circumference end (outer surface), 20b...Lead section (lead), 20c...External electrode connection section, 21...Conductor, 21b...Columnar section, 22...Conductor, 30...Magnetic core (core section), 31...T-shaped core section (first core section), 31a...Plate-shaped section, 31a1...Outer circumference end (outer surface), 31b...Columnar section, 31b1...Outer circumference end (outer surface), 32...U-shaped core section (second core section), 32a...Base section, 32b …outer wall portion (outer surface), 32c…wrapped portion, 33…wall portion (proximity outer surface), 34…wall portion (non-proximity outer surface), 100…molding die, 100a…inner surface, 101…molding die, 101a…inner surface, 130…pre-molded body material, 131…first pre-molded body, 131a…plate-shaped portion, 131a1…outer edge, 131b…columnar portion, 132…second pre-molded body, 132a…bottom surface (plate-shaped portion), 132b…wall (surrounding wall), 135…recess, 136…R surface, 136c…C surface, 200…molding die (die), 201…die base portion, 202…formed recess, 202a…bottom wall, 202b… Outer surface wall (inner wall), 220... Coil conductor (air core winding), 300... Pressurizing jig member, 301... Jig base part, 302... Jig, 302a... Jig, 302b... Jig, 302c... Jig, 302d... Relief groove, 312a... Second pre-molded body, 312b... Second pre-molded body, 312c... Second pre-molded body, 315a... Recess, 315b... Recess, 315c... Recess, DL... Length direction (first direction), DT... Thickness direction, DW... Width direction (second direction), K... Winding shaft, L... Length, L0... Axis, L1... Opening width, L2... Length, La... Normal, O... Center, P1... Center, ST1... First pre-molded body ST2...Preparation process for molded body, ST3...Coil attachment process (coil formation process), ST4...Placement process for first pre-molded body (householding process for first pre-molded body in mold), ST5...Base body formation process, ST21...Start process, ST22...Filling and heating process, ST23...Pressurizing and cooling process, ST24...End process, ST203...Coil formation process, T...Thickness, T1...Height, T2...Height, W...Width, W1...Opening width, W2...Length, θ0...Inclination angle, θ1...Inclination angle, λ1...Distance, λ2...Distance, λ3...Distance, λ11...Distance, λ12...Distance.

Claims

1. An inductor comprising a body having a core portion containing metal magnetic powder and resin, and a coil embedded inside the core portion, wherein the core portion has a first core portion having a columnar portion and a plate-shaped portion, and a second core portion covering the first core portion, the coil has a winding portion around which a conductor is wound, and a pair of lead portions drawn out from the winding portion to the outer circumference of the winding portion, at least a part of the winding portion protrudes outward from the outer circumference of the plate-shaped portion, the second core portion has a close outer circumference surface which is the outer circumference surface in close proximity to the lead portions of the coil, and a non-close outer circumference surface which is the outer circumference surface of a portion different from the close outer circumference surface, and the second core portion is formed such that the distance between the non-close outer circumference surface and the outer circumference surface of the first core portion is greater than the distance between the non-close outer circumference surface and the outer circumference surface of the winding portion of the coil.

2. The inductor according to claim 1, wherein the portion of the winding portion facing the adjacent outer surface does not protrude outward beyond the outer surface of the plate-like portion, and the portion facing the non-adjacent outer surface protrudes outward beyond the outer surface of the plate-like portion.

3. The inductor according to claim 1, wherein the conductor is a flat rectangular conductor and the winding portion is formed by α winding.

4. The inductor according to claim 1, wherein the filling rate of the metal magnetic powder in the first core portion is greater than the filling rate of the metal magnetic powder in the second core portion.

5. The inductor according to claim 1, wherein the pair of lead portions are brought out to the mounting surface of the base body.

6. The inductor according to any one of claims 1 to 5, wherein the second core portion has a portion formed on the mounting surface side of the base body in which the distance between the non-proximity outer surface and the outer surface of the first core portion is greater than the distance between the non-proximity outer surface and the outer surface of the winding portion of the coil.

7. The inductor according to claim 6, wherein the first core portion has an outer peripheral surface on the upper side of the base body that is smaller than the outer peripheral surface on the mounting side of the base body, and the second core portion has a portion formed on the upper side of the base body in which the distance between the non-proximity outer peripheral surface and the outer peripheral surface of the first core portion is greater than the distance between the non-proximity outer peripheral surface and the outer peripheral surface of the winding portion of the coil.

8. A method for manufacturing an inductor comprising a base body having a core portion containing metal magnetic powder and resin, and a coil embedded inside the core portion, comprising: a first pre-molded body preparation step of preparing a first pre-molded body containing metal magnetic powder and resin and having a columnar portion and a plate portion; a second pre-molded body preparation step of preparing a second pre-molded body having a recess on its upper surface due to an upwardly protruding wall, in a molding die with the recess facing upward; a coil forming step of forming the coil having a winding portion wound around the columnar portion of the first pre-molded body and a winding portion that protrudes outward from the outer peripheral surface of the plate portion of the first pre-molded body; and a first pre-molded body placement step of arranging the first pre-molded body such that the winding portion of the coil provided on the first pre-molded body is accommodated in the recess of the second pre-molded body. A method for manufacturing an inductor, comprising: a body forming step of thermally compressing the first pre-molded body and the second pre-molded body in a molding die to form a body having a first core portion having a columnar portion and a plate-shaped portion and a second core portion covering the first core portion.

9. The method for manufacturing an inductor according to claim 8, wherein in the first pre-molded body arrangement step, the winding portion of the coil provided on the first pre-molded body is brought into contact with the inner circumferential surface of the wall of the recess of the second pre-molded body and housed therein.

10. The method for manufacturing an inductor according to claim 8, wherein the second pre-molded body is formed such that the height of the wall of the recess is 51% or more of the height of the winding portion of the coil.

11. The method for manufacturing an inductor according to claim 8, wherein the first pre-molded body is placed in the molding die such that the distance between the outer peripheral surface of the plate-shaped portion of the base body in the width direction and the inner peripheral surface of the molding die is greater than the distance between the outer peripheral surface of the coil winding portion and the inner peripheral surface of the molding die.

12. The method for manufacturing an inductor according to claim 8, wherein in the coil forming step, the coil is formed on the first pre-molded body by winding a conductor around the columnar portion of the first pre-molded body or by inserting an air-core winding.

13. A method for manufacturing an inductor comprising a base body having a core portion containing metal magnetic powder and resin, and a coil embedded inside the core portion, comprising: a first pre-molded body preparation step of preparing a first pre-molded body containing metal magnetic powder and resin, having a plate-like portion and a columnar portion formed on the plate-like portion; a second pre-molded body forming step of filling a molding die with the pre-molded body material containing metal magnetic powder and resin, softening the pre-molded body material by heating, and then inserting a jig into the molding die to form a recess on the surface of the softened pre-molded body material, thereby forming a second pre-molded body having the recess and a peripheral wall provided around the recess; and a coil mounting step of attaching the coil to the first pre-molded body such that the columnar portion of the first pre-molded body is inserted into the winding portion of the coil. A method for manufacturing an inductor, comprising: a first pre-molded body mold housing step of housing the first pre-molded body, to which the coil is attached, in a molding die such that the outer circumference of the winding portion of the coil is close to the inner circumferential surface of the peripheral wall of the second pre-molded body; and a base body forming step of thermally compressing the first pre-molded body and the second pre-molded body in the molding die to form a base body having a core portion having a plate-like portion and a columnar portion formed on the plate-like portion, a second core portion covering the first core portion, and the coil embedded inside the core portion.

14. The method for manufacturing an inductor according to claim 13, wherein, in the first pre-molded body mold housing step, the first pre-molded body to which the coil is attached is housed in the molding die such that the outer circumference of the winding portion of the coil contacts the inner circumferential surface of the peripheral wall of the second pre-molded body.

15. The method for manufacturing an inductor according to claim 13, wherein in the first pre-molded body mold housing step, a wire is wound around the columnar portion of the first pre-molded body to attach the coil having a wound portion in which at least a portion of the outer circumference protrudes outward from the outer peripheral surface of the plate-shaped portion of the first pre-molded body.

16. The method for manufacturing an inductor according to claim 13, wherein in the first pre-molded body mold housing step, the winding portion of the coil is attached to the columnar portion of the first pre-molded body, thereby attaching the coil, which has a winding portion that protrudes outward from at least a portion of the outer peripheral surface of the plate-shaped portion of the first pre-molded body, to the first pre-molded body.

17. The method for manufacturing an inductor according to any one of claims 13 to 16, wherein a tapered surface is formed on the inner circumferential surface of the peripheral wall of the second pre-molded body, the tapered surface having an inclination angle of 15° or less with respect to the normal to the bottom surface of the second pre-molded body.

18. The method for manufacturing an inductor according to claim 13, wherein the molding die is a rectangular mold having opening widths in a first direction and a second direction that are orthogonal to each other, the length of the jig in the first direction passing through the center of the jig is 65% to 98% of the opening width in the first direction passing through the center of the molding die, the length of the jig in the second direction passing through the center of the jig is 65% to 98% of the opening width in the second direction passing through the center of the molding die, and when inserting the jig into the molding die, the jig is inserted without contacting the inner wall of the molding die.

19. The method for manufacturing an inductor according to claim 13, wherein the shape of the recess in the second pre-molded body is circular.

20. The method for manufacturing an inductor according to claim 13, wherein the shape of the recess in the second pre-molded body is elliptical.

21. The method for manufacturing an inductor according to claim 13, wherein the shape of the recess in the second pre-molded body is polygonal.

22. The method for manufacturing an inductor according to claim 21, wherein one or more corners of the shape of the recess in the second pre-molded body are R-shaped or C-shaped.

23. The method for manufacturing an inductor according to claim 15, wherein the leads of the coil are brought out to the mounting surface of the base body.

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