Method for manufacturing inductor

Abstract

The present invention enables, in an inductor having a coil embedded in an element body, use of a larger size coil by suppressing deformation and positional variation of the coil during pressure molding of the element body.　A method for manufacturing an inductor having an element body containing magnetic particles and a resin, and a coil embedded inside the element body, the method includes: a preliminary molded body production step of producing a first preliminary molded body having a plate-like portion and a columnar portion protruding from the plate-like portion, and a bottomed cylindrical second preliminary molded body having a recess, each containing magnetic particles and a resin; a coil assembly step of winding a conductive wire around the columnar portion of the first preliminary molded body to form the coil, and arranging both end portions of the conductive wire on a side surface of the plate-like portion; and a pressure-molding step of pressure-molding the entirety of the first preliminary molded body and the second preliminary molded body in a molding die, in a state where the columnar portion of the first preliminary molded body is inserted together with the coil into the recess of the second preliminary molded body.

Description

Method for manufacturing an inductor

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

[0002] An inductor is known that includes a body containing magnetic particles and a resin, and a coil embedded in the body, and an external electrode is formed on the surface of the body to be electrically connected to the lead-out end of the coil (see, for example, Patent Document 1).

[0003] Conventionally, as a method for manufacturing this type of inductor, two preformed bodies constituting the body and a coil in which a conductor is wound in a spiral shape are produced, and the coil is sandwiched between the two preformed bodies and heat-formed in a molding die. Thus, the coil is embedded in the body. For example, one of the two preformed bodies is provided with a protrusion that serves as the center of the spiral coil, and when the coil is sandwiched between the two preformed bodies, the protrusion is inserted into the hollow portion of the spiral coil. An appropriate gap (clearance) is provided between the hollow portion and the protrusion so that the protrusion can be smoothly inserted into the hollow portion of the coil.

[0004] However, in the above conventional manufacturing method, due to the existence of the gap between the hollow portion and the protrusion, during heat and pressure molding in the molding die, deformation of the coil and variation in the position of the coil with respect to the protrusion occur. The deformation of the coil can be a deformation in the direction of decreasing the inner diameter of the coil due to the collapse of the gap between the hollow portion and the protrusion, or a deformation in the direction of expanding the inner diameter of the coil due to the magnetic particles and resin of the preformed body entering the gap.

[0005] Further, in the conventional method for manufacturing an inductor, due to the existence of the gap, the coil can slightly rotate around the protrusion during heat and pressure molding in the molding die. As a result, variation can occur in the position of the lead wire end portion of the coil in the body after heat and pressure molding.

[0006] Therefore, in order to ensure an appropriate wall thickness between the outer circumference of the coil and the surface of the base body after heat and pressure molding, it may be necessary to design the outer diameter of the coil to be smaller in advance, taking into account the expansion deformation, positional shift, and positional variations of the lead wire ends of the coil. As a result, the electrical characteristics that can be realized as an inductor may be reduced.

[0007] Korean Published Patent Publication No. 20140038781

[0008] The objective of the present invention is to enable the use of larger coils in an inductor having a coil embedded within a body by suppressing deformation and positional variations of the coil during the pressure molding of the body.

[0009] One aspect of the present invention is a method for manufacturing an inductor having a base body containing magnetic particles and resin, and a coil embedded inside the base body, comprising: a pre-molded body manufacturing step of manufacturing a first pre-molded body having a plate-like portion and a columnar portion protruding from the plate-like portion, and a second bottomed cylindrical pre-molded body having a recess, each containing magnetic particles and resin; a coil assembly step of winding a conductor around the columnar portion of the first pre-molded body to form a coil, and arranging both ends of the conductor on the side surface of the plate-like portion; and a pressure molding step of inserting the columnar portion of the first pre-molded body together with the coil into the recess of the second pre-molded body, and then pressure molding the entire first pre-molded body and the second pre-molded body in a molding die. This specification shall include all the contents of Japanese Patent Application No. 2024-220523, filed on December 17, 2024.

[0010] According to the present invention, in an inductor having a coil embedded within a body, deformation and positional variations of the coil during the pressure molding of the body are suppressed, making it possible to use a larger size coil.

[0011] Figure 1 is a perspective view of an inductor that can be manufactured by the inductor manufacturing method according to one embodiment of the present invention, viewed from the top surface of the inductor. Figure 2 is a perspective view of the inductor viewed from the mounting surface. Figure 3 is a perspective view showing the internal structure of the inductor. Figure 4 is a flowchart showing the steps of the inductor manufacturing method according to one embodiment of the present invention. Figure 5 is a diagram showing an example of the structure of an intermediate product of the inductor manufactured in each step from the pre-molded body manufacturing step to the pressure molding step. Figure 6 is a diagram showing an example of the arrangement of the lead-out portion on the side surface of the plate-shaped portion of the first pre-molded body. Figure 7 is a diagram showing another example of the arrangement of the lead-out portion on the side surface of the plate-shaped portion of the first pre-molded body.

[0012] Embodiments of the present invention will be described below with reference to the drawings. [1. Inductor Configuration] First, an example of the configuration of an inductor manufactured by the manufacturing method according to this embodiment will be described. Figures 1, 2, and 3 are diagrams showing the configuration of an inductor 1 that can be manufactured by the manufacturing method according to this embodiment. Figure 1 is a perspective view of the inductor 1 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 mounting surface 10 facing the top surface 12. Figure 3 is a perspective view showing the internal configuration of the inductor 1.

[0013] The inductor 1 comprises a base body 2 containing magnetic particles and resin, and a coil 20 embedded inside the base body 2 (Figure 3). The inductor 1 is configured as a surface-mount type electronic component, and a pair of external electrodes 4 are provided on the surface of the base body 2, which is a roughly rectangular parallelepiped shape that is one aspect of a roughly hexahedron shape (Figure 2).

[0014] In this embodiment, in the base body 2, the first main surface that faces the mounting substrate (e.g., a circuit board) not shown during mounting is defined as the mounting surface 10, the second main surface facing the mounting surface 10 is called the top surface 12, the pair of third main surfaces perpendicular to the mounting surface 10 are called end surfaces 14, and the pair of fourth main surfaces perpendicular to these mounting surfaces 10 and the pair of end surfaces 14 are called side surfaces 16. As shown in Figure 1, the distance from the mounting 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 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.

[0015] The base body 2 includes a coil 20 and a roughly hexahedral core 30 in which the coil 20 is embedded. The core 30 is a molded body that is compressed into a roughly hexahedral shape by pressurizing and heating a mixed powder of magnetic particles and resin while the coil 20 is enclosed inside.

[0016] Furthermore, the magnetic particles are powdered metallic magnetic particles. The metallic magnetic particles have an insulating film covering their surface with a thickness of several nanometers to tens of nanometers. By covering the metallic magnetic particles with an insulating film, the insulation resistance and dielectric strength are increased.

[0017] Examples of metallic magnetic particles that can be used include Fe-Si-Cr alloy powder, Cr-free Fe-Si alloy powder, Fe-Ni-Al alloy powder, Fe-Cr-Al alloy powder, Fe-Si-Al alloy powder, Fe-Ni alloy powder, and Fe-Ni-Mo alloy powder.

[0018] For example, zinc phosphate glass may be used as the insulating film covering the metallic magnetic particles. Alternatively, other phosphates (such as magnesium phosphate, calcium phosphate, manganese phosphate, and cadmium phosphate) or resin materials (such as silicone resins, epoxy resins, phenolic resins, polyamide resins, polyimide resins, and polyphenylene sulfide resins) may be used as the insulating film.

[0019] As an example, the resin material used in the mixed powder may be an epoxy resin mainly composed of bisphenol A type epoxy resin. The epoxy resin may also be a phenol novolac type epoxy resin. The resin content in the mixed powder is, for example, 3 wt%.

[0020] The above-mentioned resin material may not be epoxy resin, and may be two or more types instead of just one. For example, in addition to epoxy resin, thermosetting resins such as phenolic resin, polyester resin, polyimide resin, and polyolefin resin can be used as the resin material.

[0021] The coil 20 is formed from a conductor wire CW. As shown in Figure 3, the coil 20 comprises a winding section 22 around which the conductor wire CW is wound, and a pair of lead-out sections 24 drawn out from the winding section 22. The winding section 22 is formed by winding the conductor wire CW in a spiral shape such that both ends of the conductor wire CW are located on the outer circumference and connected to each other on the inner circumference.

[0022] The conductor CW is, for example, a conductor with a rectangular cross-section (a so-called flat-angle conductor). The conductor CW has an insulating coating on the surface of the conductor with a rectangular cross-section. The conductor CW also has a fusion layer on top of the insulating coating for bonding the overlapping conductors in the winding portion 22. The insulating coating is formed of polyurethane resin, polyester resin, epoxy resin, or polyimidoamide resin. The fusion layer is formed of polyamide resin, and may be formed of two types of polyamide resins with different molecular weights. Furthermore, the thickness of the insulating coating is 2 μm to 20 μm, preferably 2 μm to 8 μm, more preferably 4 μm to 6 μm, and the thickness of the fusion layer is 1 μm to 25 μm, preferably 2 μm to 25 μm, more preferably 2 μm to 4 μm.

[0023] Inside the base body 2, the coil 20 is embedded in the core 30 with the central axis of the winding portion 22 aligned with the thickness direction DT of the base body 2, and each of the lead-out portions 24 is drawn out from the winding portion 22 to the mounting surface 10 and electrically connected to the external electrodes 4. On the mounting surface 10, the intermediate region 10b between the two electrode regions 10a, which are areas where the external electrodes 4 are provided, is recessed relative to the electrode regions 10a. This prevents solder from flowing from one external electrode 4 to the other external electrode 4 when mounting the inductor 1 onto a circuit board or the like.

[0024] Inductor 1 with this configuration can improve DC superposition characteristics by using soft magnetic particles, and is therefore 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. It 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, and it can also be used in tuning circuits, filter circuits, and rectifier / smoothing circuits, for example.

[0025] The inductor 1 may have a protective layer (not shown) covering the entire surface of the base body 2, excluding the area of ​​the external electrode 4. The material for the protective layer can be, for example, a thermosetting resin such as epoxy resin, polyimide resin, or phenolic resin, or a thermoplastic resin such as polyethylene resin or polyamide resin. These resins may further contain fillers such as silicon dioxide or titanium dioxide.

[0026] [2. Method for Manufacturing an Inductor] Figure 4 is a diagram showing the steps of a method for manufacturing an inductor according to one embodiment of the present invention. The method for manufacturing an inductor according to this embodiment includes a pre-molded body manufacturing step S1, a coil assembly step S2, a pressure molding step S3, a barrel polishing step S4, and an external electrode formation step S5. Figure 5 is a diagram showing an example of the configuration of an intermediate product of the inductor 1 manufactured in each step from the pre-molded body manufacturing step S1 to the pressure molding step S3.

[0027] The pre-molded body manufacturing step S1 is a step of forming a first pre-molded body 40 and a second pre-molded body 41, each containing magnetic particles and resin. The first pre-molded body 40 and the second pre-molded body 41 are each molded into an easy-to-handle solid form by pressurizing the above-mentioned mixed powder, which is the material for the base body 2, in a mold.

[0028] In this embodiment, the first pre-molded body 40 has a T-shaped cross-section and a plate-like portion 40a that is substantially rectangular in plan view, and a columnar portion 40b that protrudes from the center of the plate-like portion 40a in plan view. The second pre-molded body 41 is bottomed and has a recess 41a on one of its main faces, which has a substantially hexahedral outer shape.

[0029] The coil assembly process S2 is the process of assembling the conductor CW to the first pre-molded body 40. The coil assembly process S2 includes the coil winding process S21 and the lead-out portion arrangement process S22. In the coil winding process S21, the conductor CW is wound around the columnar portion 40b of the first pre-molded body 40 to form the coil 20. The conductor CW is, for example, alpha-wound around the columnar portion 40b of the first pre-molded body 40, and the winding portion 22 of the coil 20 is formed around the columnar portion 40b. The ends of the conductor CW that correspond to the beginning and end of the winding of the coil 20 become a pair of lead-out portions 24 extending from the outer circumference of the winding portion 22.

[0030] In the lead-out section arrangement step S22, the two lead-out sections 24, which are both ends of the conductor CW, are placed on the side surfaces of the plate-shaped section 40a of the first pre-molded body 40. The side surfaces of the plate-shaped section 40a on which the two lead-out sections 24 are placed may be, for example, two opposing side surfaces of the plate-shaped section 40a, which has a substantially rectangular shape in plan view.

[0031] In this embodiment, the two lead-out portions 24, which are the ends of the conductor CW, are bent in the width direction of the conductor CW and are arranged on the side surface 43 of the plate-shaped portion 40a of the first pre-molded body 40.

[0032] Figure 6 is an enlarged view of the intermediate product in the drawer section arrangement process (S22) shown in Figure 5, and shows an example of the arrangement of the drawer section 24 on the side surface of the plate-shaped portion 40a of the first pre-molded body 40. In Figure 6, of the plate-shaped portion 40a of the first pre-molded body 40, the second main surface opposite the first main surface on which the columnar portion 40b is provided is called the upper surface 42, the third main surface perpendicular to the upper surface 42 is called the side surface 43, and the pair of fourth main surfaces perpendicular to the upper surface 42 and the pair of side surfaces 43 are called side surfaces 44.

[0033] The top surface 42 corresponds to the mounting surface 10 of the inductor 1 when completed. The side surfaces 43 and 44 are surfaces that are aligned with the end face 14 and side surface 16 of the inductor 1 when completed, respectively. The lower part of Figure 6 shows the various directions of the inductor 1 when completed.

[0034] As shown in Figure 6, in the lead-out section arrangement step S22, first, the two lead-out sections 24, which are both ends of the conductor CW, are bent at approximately a right angle toward the closer of the two side surfaces 43 of the plate-shaped section 40a and positioned to contact that side surface 43. Then, the lead-out sections 24 are pressed against the plate-shaped section 40a at the contact position with the side surface 43.

[0035] The crimping can be performed, for example, by pressing the drawer portion 24 against the side surface 43 using a jig, heating the jig for a predetermined time, and partially heating the side surface 43 through the drawer portion 24. When heated, the resin softens and melts in the heated portion of the fused layer of the drawer portion 24 and the side surface 43 of the plate-like portion 40a, causing the drawer portion 24 to sink into the interior of the plate-like portion 40a. After the heating stops, the resin hardens, fixing the drawer portion 24 to the side surface 43 of the plate-like portion 40a. Next, the excess length of the drawer portion 24 that protrudes from the upper surface 42 of the plate-like portion 40a is cut off, and the cut surface of the drawer portion 24 is trimmed flush with the upper surface 42 of the plate-like portion 40a. The cut surface of the extraction portion 24 is electrically connected to the external electrode 4 formed on the upper surface 42 of the plate-shaped portion 40a (corresponding to the mounting surface 10 of the base body 2) in the subsequent external electrode formation step S5.

[0036] Figure 7 shows another example of the arrangement of the drawer portion 24 on the side surface of the plate-like portion 40a of the first pre-molded body 40, as a modified example. Figure 7 shows a modified example of the intermediate product in the drawer portion arrangement process (S22) shown in Figure 5, enlarged in the same way as in Figure 6. In Figure 7, components that are the same as those shown in Figure 6 are indicated by the same reference numerals as those shown in Figure 6, and the explanation of Figure 6 described above will be used with reference.

[0037] In the example shown in Figure 7, the lead-out portions 24, which are both ends of the conductor CW, are arranged along the extending direction of the side surface 43 of the plate-shaped portion 40a. For example, a portion of the surface of the conductor CW in the part of the lead-out portion 24 that is arranged along the extending direction of the side surface 43 of the plate-shaped portion 40a is flush with the upper surface 42 of the plate-shaped portion 40a.

[0038] Then, the portion of the pull-out section 24 that is positioned along the extending direction of the side surface 43 of the plate-shaped section 40a is pressed against the said side surface 43 of the plate-shaped section 40a. The pressing can be performed in the same manner as described above. After that, the excess length of the pull-out section 24 that protrudes from the side surface 44 of the plate-shaped section 40a, which has been pressed against the side surface 43, is cut off, and the cut surface of the pull-out section 24 is trimmed flush with the side surface 44.

[0039] The surface of the lead portion 24 exposed from the upper surface 42 of the plate-shaped portion 40a is electrically connected to the external electrode 4 formed on the upper surface 42 of the plate-shaped portion 40a (corresponding to the mounting surface 10 of the base body 2) in the subsequent external electrode formation process S5. Compared to the configuration shown in Figure 6, the configuration shown in Figure 7 has a larger area of ​​the lead portion 24 exposed on the upper surface 42 of the plate-shaped portion 40a where the external electrode 4 is formed, thus reducing the DC resistance of the inductor 1.

[0040] Referring to Figures 4 and 5, the first pre-molded body 40, to which the coil 20 is assembled in the coil assembly process S2, is integrated with the second pre-molded body 41 in the pressure molding process S3. In the pressure molding process S3, with the columnar portion 40b of the first pre-molded body 40 inserted together with the coil 20 into the recess 41a of the second pre-molded body 41, the entire first pre-molded body 40 and the second pre-molded body 41 are heated and pressure-molded in a molding die to integrate them. As a result, a base body 2 is formed with the coil 20 enclosed within a core 30 formed from the first pre-molded body 40 and the second pre-molded body 41.

[0041] Referring to Figure 4, in the barrel polishing process S4 following the pressure molding process S3, the corners of the molded core 30 are rounded. The barrel-polished core 30 may also be polished on its bottom and sides. Furthermore, the core 30 whose bottom and sides have been polished may be coated with a protective film on its surface. The protective film coating can be performed by spraying a resin solution that will form the protective layer into the barrel tank.

[0042] The external electrode formation step S5 is a step of forming an external electrode 4 on the mounting surface 10 of the core 30 (corresponding to the upper surface 42 of the plate-shaped portion 40a of the first pre-molded body 40) where a part of the lead portion 24 of the coil 20 is exposed. The external electrode formation step S5 includes a surface treatment step S51, a conductive resin layer formation step S52, and a plating layer formation step S53.

[0043] The surface treatment step S51 is a step of modifying the surface of the planned electrode location by irradiating the planned electrode location (see FIG. 2) of the mounting surface 10 of the core 30 with laser light. Here, the planned electrode location refers to the range on the surface of the core 30 where the external electrode 4 is to be formed, including the portion where the lead-out portion 24 is exposed. Specifically, by irradiating laser light, the resin on the surface of the core 30 is removed within the range of the planned electrode location, and the insulating film on the surface of the magnetic particles protruding from the core 30 is removed. As a result, the portion of the surface of the core 30 at the planned electrode location has a larger exposed area of the metal of the magnetic particles per unit area of the surface of the core 30 compared to other surface portions of the core 30. Note that after laser irradiation, a cleaning process (e.g., etching process) for cleaning the surface of the planned electrode location may be performed.

[0044] In the conductive resin layer forming step S52, a paste-like conductive resin containing conductive powder and resin is applied to the planned electrode location and dried and cured to form a conductive resin layer. Such a conductive resin layer contains conductive powder, so it can form a uniform potential distribution at the planned electrode location in the plating layer forming step described later, and thus the homogeneity of the plating layer formed on the conductive resin layer can be improved.

[0045] In the plating layer forming step S53, a plating layer is formed on the surface of the conductive resin layer. The plating layer is composed of a first plating layer formed directly on the surface of the conductive resin layer and a second plating layer formed on the first plating layer. As an example, the first plating layer is a nickel (Ni) plating layer with a thickness of 4.0 μm or more and 15 μm or less, and the second plating layer is a tin (Sn) plating layer with a thickness of 4 μm or more and 8 μm or less. The plating layer can be formed by electrolytic plating (e.g., barrel plating). Note that although the plating layer is configured with two layers in this embodiment, it is not limited to this, and it can be configured with an arbitrary number of layers.

[0046] In the method for manufacturing an inductor having the above-described steps, before the pressure molding of the base body 2 (specifically, the core 30), the coil 20 is assembled without a gap to the columnar portion 40b of the first preform 40 that will form a part of the base body 2 in advance, and the lead-out portion 24 of the coil 20 is arranged on the side surface 43 of the plate-like portion 40a of the first preform 40. Therefore, during the pressure molding of the base body 2, the inner diameter and position of the winding portion 22 of the coil 20 are regulated by the columnar portion 40b, and the position of the lead-out portion 24 is constrained by the side surface 43 of the plate-like portion 40a. Thus, deformation of the coil 20 and movement of the position of the coil 20 within the base body 2 during the pressure molding of the base body 2 are suppressed. Accordingly, according to the method for manufacturing an inductor of the present embodiment, compared with the conventional manufacturing method in which the coil and the preform are separately formed, combined, and pressure molded, the manufacturing variation in the outer diameter of the winding portion 22 of the coil 20 and the manufacturing variation in the wall thickness between the outer periphery of the winding portion 22 and the surface of the base body 2 during the pressure molding of the base body 2 are suppressed to a small extent, and the use of a coil 20 of a larger size becomes possible.

[0047] Also, according to the method for manufacturing an inductor of the present embodiment, since deformation of the winding portion 22 of the coil 20 during the pressure molding of the base body 2 is suppressed, the manufacturing variation in the inductance and the DC superposition resistance of the manufactured inductor 1 is suppressed. Further, according to the method for manufacturing an inductor of the present embodiment, since the pressure molding of the base body 2 is performed with the position of the lead-out portion 24 constrained by the side surface 43 of the plate-like portion 40a, the manufacturing variation in the area of the lead-out portion 24 that is exposed on the upper surface 42 of the plate-like portion 40a (and thus, the mounting surface 10 of the base body 2) and contacts the external electrode 4 is suppressed. As a result, according to the method for manufacturing an inductor of the present embodiment, the manufacturing variation in the DC resistance of the manufactured inductor 1 is also suppressed.

[0048] Here, from the viewpoint of suppressing deformation of the coil 20 and movement of the position of the coil 20 within the base body 2 during the pressure molding of the base body 2, it is preferable that the hardness of the first preform 40 having the columnar portion 40b that regulates the inner diameter of the winding portion 22 and the plate-like portion 40a that constrains the position of the lead-out portion 24 is higher than the hardness of the second preform 41. Alternatively, it is preferable that the viscosity of the first preform 40 during the pressure molding is higher than the viscosity of the second preform 41.

[0049] For example, by making the average particle size of the magnetic particles in the first pre-molded body 40 smaller than the average particle size of the magnetic particles in the second pre-molded body 41, the hardness or viscosity of the first pre-molded body 40 can be made greater than that of the second pre-molded body 41. Specifically, it is preferable that the average particle size of the magnetic particles contained in the first pre-molded body 40 and the average particle size of the magnetic particles contained in the second pre-molded body 41 are in the range of 4 μm to 20 μm and 4 μm to 35 μm, respectively. Furthermore, it is preferable that the average particle size of the magnetic particles contained in the first pre-molded body 40 and the average particle size of the magnetic particles contained in the second pre-molded body 41 are in the range of 10 μm ± 1 μm and 30 μm ± 3 μm, respectively.

[0050] [3. Other Embodiments and Modifications] The arrangement of the pull-out portion 24 on the side surface 43 of the plate-shaped portion 40a of the first pre-molded body 40 is not limited to the configurations shown in Figures 6 and 7. The pull-out portion 24 can be arranged on the side surface 43 of the plate-shaped portion 40a in any configuration, as long as it is possible to connect it to the external electrode 4 formed on the upper surface 42 of the plate-shaped portion 40a.

[0051] Preferably, the pull-out portion 24 is positioned on the side surface 43 such that at least a part of it is exposed from the upper surface 42. This avoids the need for additional steps after the formation of the base body 2, such as polishing the mounting surface 10 to expose the pull-out portion 24.

[0052] Furthermore, the magnetic particles contained in the first pre-molded body 40 and the second pre-molded body 41 may include multiple types of magnetic particles with different average particle sizes.

[0053] Furthermore, the conductor CW is not limited to a rectangular conductor. In other embodiments, the conductor CW may be, for example, a round wire with a circular cross-section.

[0054] Furthermore, the external electrode 4 is not limited to a bottom electrode formed only on the mounting surface 10, but may also be an L-shaped electrode extending from the mounting surface 10 to the end surface 14.

[0055] Furthermore, the external electrode formation step S5 does not necessarily require the conductive resin layer formation step S52. In that case, the next step, the plating layer formation step S53, directly applies plating to the surface of the base body at the planned electrode locations, and the external electrode is formed by a copper plating layer, a nickel (Ni) plating layer formed on the copper plating layer, and a tin (Sn) plating layer formed on the nickel (Ni) plating layer.

[0056] Furthermore, unless otherwise specified, the horizontal and vertical directions, various numerical values, shapes, and materials in the embodiments described above include a range that produces the same effects as those directions, numerical values, shapes, and materials (the so-called equivalence range).

[0057] [4. Configurations Supported by the Above Embodiments] The above embodiments and modifications support the following configurations.

[0058] (Configuration 1) A method for manufacturing an inductor having a base body containing magnetic particles and resin, and a coil embedded inside the base body, comprising: a pre-molded body manufacturing step of manufacturing a first pre-molded body having a plate-like portion and a columnar portion protruding from the plate-like portion, and a second pre-molded body having a bottomed cylindrical shape with a recess, each containing magnetic particles and resin; a coil assembly step of winding a conductor around the columnar portion of the first pre-molded body to form a coil and arranging both ends of the conductor on the side surface of the plate-like portion; and a pressure molding step of inserting the columnar portion of the first pre-molded body together with the coil into the recess of the second pre-molded body and pressure molding the entire first pre-molded body and the second pre-molded body in a molding die. In the inductor manufacturing method of Configuration 1, before the pressure molding of the base body, a coil is assembled by winding a conductor around the columnar portion of a first pre-molded body that constitutes a part of the base body, and both ends of the conductor are positioned on the side surface of the plate-shaped portion of the first pre-molded body. Therefore, during the pressure molding of the base body, the inner diameter and position of the coil are restricted by the columnar portion, and the positions of both ends of the conductor are constrained by the side surface of the plate-shaped portion, thereby suppressing deformation of the coil and movement of the coil's position within the base body during the pressure molding of the base body. Consequently, compared to conventional manufacturing methods in which the coil and the pre-molded body are formed separately and then combined and pressure-molded, the inductor manufacturing method of Configuration 1 suppresses manufacturing variations in the outer diameter of the coil and the wall thickness between the outer circumference of the coil and the surface of the base body during the pressure molding of the base body, making it possible to use larger sized coils.

[0059] (Configuration 2) The method for manufacturing an inductor according to Configuration 1, wherein in the coil assembly step, both ends of the conductor are arranged along the extending direction of the side surface of the plate-shaped portion of the first pre-molded body. According to the method for manufacturing an inductor of Configuration 2, the length of the portion exposed on the upper surface of the plate-shaped portion on which the external electrodes are formed at both ends of the conductor can be increased, thereby increasing the contact area with the external electrodes and reducing the DC resistance of the inductor 1.

[0060] (Configuration 3) The method for manufacturing an inductor according to Configuration 1 or 2, wherein the conductor is a conductor with a rectangular cross-section, and in the coil assembly process, both ends of the conductor are bent in the width direction of the conductor and arranged on the side surface of the plate-shaped portion of the first pre-molded body. According to the method for manufacturing an inductor of Configuration 3, when the conductor constituting the coil is a conductor with a rectangular cross-section, the main surface of the conductor can be arranged on the side surface of the plate-shaped portion of the first pre-molded body, thereby ensuring high bonding strength between the conductor and the side surface of the plate-shaped portion.

[0061] (Configuration 4) A method for manufacturing an inductor according to any one of Configurations 1 to 3, wherein the hardness of the first pre-molded body is higher than that of the second pre-molded body. According to the method for manufacturing an inductor of Configuration 4, deformation of the columnar portion of the first pre-molded body during pressure molding of the base body can be further suppressed, thereby further suppressing deformation of the coil and movement of the coil's position within the base body.

[0062] 1...Inductor, 2...Base body, 4...External electrode, 10...Mounting surface, 12...Top surface, 14...End face, 16...Side side, 20...Coil, 22...Winding section, 24...Outlet section, 30...Core, 40...First pre-molded body, 40a...Plate-shaped section, 40b...Columnar section, 41...Second pre-molded body, 41a...Recess, 42...Top surface, 43, 44...Side side, CW...Conducting wire.

Claims

1. A method for manufacturing an inductor having a base body containing magnetic particles and resin, and a coil embedded inside the base body, comprising: a pre-molded body manufacturing step of manufacturing a first pre-molded body having a plate-like portion and a columnar portion protruding from the plate-like portion, and a second pre-molded body having a bottomed cylindrical shape with a recess, each containing magnetic particles and resin; a coil assembly step of winding a conductor around the columnar portion of the first pre-molded body to form a coil, and arranging both ends of the conductor on the side surface of the plate-like portion; and a pressure molding step of inserting the columnar portion of the first pre-molded body together with the coil into the recess of the second pre-molded body, and then pressure molding the entire first pre-molded body and the second pre-molded body in a molding die.

2. The method for manufacturing an inductor according to claim 1, wherein in the coil assembly step, both ends of the conductor are arranged along the extending direction of the side surface of the plate-shaped portion of the first pre-molded body.

3. The method for manufacturing an inductor according to claim 1 or 2, wherein the conductor is a conductor having a rectangular cross-section, and in the coil assembly step, both ends of the conductor are bent in the width direction of the conductor and arranged on the side surface of the plate-shaped portion of the first pre-molded body.

4. The method for manufacturing an inductor according to any one of claims 1 to 3, wherein the hardness of the first pre-molded body is higher than the hardness of the second pre-molded body.

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