Method for manufacturing coil component and coil component

Abstract

A method for manufacturing a coil component (1) includes a coil accommodating step, a preliminary molding step, an arranging step, and a curing step. In the preliminary molding step, a kneaded material in which a thermosetting resin and magnetic powder are kneaded is molded into a preliminary molded body (40) having a predetermined shape. In the arranging step, one or more preliminary molded bodies (40) are arranged in an accommodating recess (22) of a case (20). In the curing step, a core molded body (30) is formed by pressurizing and heating the preliminary molded body (40) arranged in the accommodating recess (22) to cure the preliminary molded body (40). The predetermined shape of the preliminary molded body (40) is a shape along a gap portion (24) that is at least a part of a space inside the accommodating recess (22) in which a coil (10) is accommodated in the coil accommodating step. In the arranging step, the preliminary molded body (40) is arranged in the gap portion (24).

Description

Method for manufacturing coil component and coil component

[0001] The present invention relates to a method for manufacturing a coil component and a coil component.

[0002] The core used in the coil component is manufactured from a mixture containing magnetic powder and resin. Regarding this type of technology, Patent Document 1 below discloses that a mixture (200) obtained by mixing magnetic powder, resin, and a solvent such as acetone is put into a container, and the mixture (200) is cured by applying pressure or the like to form a magnetic core (30). The mixture (200) can be deformed into a shape such as a coil assembly (20) through a process such as pressurization and can enter the gap in the container.

[0003] Japanese Patent Application Laid-Open No. 2018-133434

[0004] In order to put the mixture (200) into a predetermined container and deform the mixture along the shape of another member such as the coil assembly (20) through a process such as pressurization and sufficiently fill the container, the mixture (200) needs to have a fluidity of a predetermined level or more. For this purpose, a predetermined amount of solvent is added to the mixture (200). However, when the solvent is added, the proportion of magnetic powder in the entire core decreases, so the magnetic characteristics of the coil component may deteriorate.

[0005] The present invention has been made in view of the above problems, and provides a coil component in which the core is well filled in a container and the deterioration of magnetic characteristics is suppressed, and a method for manufacturing the coil component.

[0006] The present invention provides a method for manufacturing a coil component comprising: a coil; a case having a bottomed housing recess for housing the coil; and a core molded body containing magnetic powder and disposed in the housing recess, the method comprising: a coil housing step of housing the coil in the housing recess; a pre-molding step of forming a pre-molded body having a predetermined shape from a kneaded material of a thermosetting resin and the magnetic powder; a placement step of arranging one or more of the pre-molded bodies in the housing recess of the case; and a curing step of forming the core molded body by pressurizing and heating the pre-molded bodies disposed in the housing recess to cure them, wherein the predetermined shape of the pre-molded body is a shape that follows a gap portion which is at least a part of the internal space of the housing recess in which the coil is housed in the coil housing step, and the pre-molded body is placed in the gap portion in the placement step.

[0007] The coil component of the present invention comprises a coil, a case having a bottomed housing recess for housing the coil, and a core molded body disposed in the housing recess and containing resin and magnetic powder, wherein the core molded body contains voids, and the porosity, which is the ratio of the volume of the voids to the envelope volume of the core molded body, is 35.0% or more.

[0008] In the method for manufacturing a coil component of the present invention, a temporary molded body is formed to conform to the gaps within the case, and then the temporary molded body is placed in the gaps within the case. As a result, the gaps within the case are well filled with the temporary molded body, and the core is well filled into the case. Furthermore, because the temporary molded body is pre-formed to conform to the gaps within the case, the temporary molded body does not need to have high fluidity compared to the case in which a mixture of magnetic powder and resin is introduced into the case and the mixture is distributed throughout the gaps within the case. Therefore, the amount of solvent added to the temporary molded body can be reduced or eliminated, thereby suppressing a decrease in magnetic properties. This makes it possible to provide a coil component in which the core is well filled into the container and the decrease in magnetic properties is suppressed.

[0009] The aforementioned objectives, as well as other objectives, features, and advantages, will become even clearer from the preferred embodiments described below and the accompanying drawings.

[0010] This is a perspective view showing an example of a coil component according to the first embodiment of the present invention. This is an exploded perspective view of the coil component according to the first embodiment. This is a top view of the coil component according to the first embodiment. The outer shapes of the core molded body, coil, and coil body are shown by dotted lines. This is a cross-sectional view of the cross section in Figure 3 along the arrow IV-IV, where the dashed line is located. Figure 5(a) is a longitudinal cross-sectional view of the coil and core molded body according to the first embodiment. Figure 5(b) is a longitudinal cross-sectional view of the coil and core molded body according to the second embodiment. Figures 6(a) and 6(b) are photographs of the cross section of the core molded body to explain the porosity in the core molded body. Figures 7(a) and 7(c) are photographs of the top surface of the core molded body to explain the recess occupancy rate on the top surface of the core molded body. Figure 7(b) is an enlarged view of the area within frame VIIb shown by the dashed line in Figure 7(a). This is a perspective view of a coil component according to the third embodiment. The outer shape of the core molded body is shown by dotted lines. This is an exploded perspective view of the coil component according to the third embodiment. This is a cross-sectional view of the coil component according to the third embodiment, and is a cross-sectional view of the cross section corresponding to Figure 4. This is a top view of a coil component according to the third embodiment. The outer shape of the coil and core is shown by dotted lines. Figure 12(a) is a diagram illustrating the manufacturing method of a coil component according to the fourth embodiment, and is a top view of the coil component in the manufacturing process. Figure 12(b) is a perspective view of a core molded body according to the fourth embodiment.

[0011] The various components of the coil component of the present invention do not need to be independent entities; it is permissible for multiple components to be formed as a single member, for one component to be formed from multiple members, for one component to be part of another component, for parts of one component to overlap with parts of another component, and so on. Furthermore, while the method for manufacturing the coil component of the present invention may be described using multiple steps described in order, the order of description does not limit the order or timing of the execution of the multiple steps. For this reason, when implementing the method for manufacturing the coil component of the present invention, the order of the multiple steps can be changed to the extent that it does not impede the content, and some or all of the execution timing of the multiple steps may overlap with each other.

[0012] Embodiments of the present invention will be described below with reference to the drawings. In each drawing, corresponding components are denoted by the same reference numeral, and redundant explanations will be omitted as appropriate. In this embodiment, the directions of front, back, left, right, up, and down are defined and described as shown in the figures. However, this is defined for convenience in order to briefly explain the relative relationships of the components and does not limit the direction during manufacturing or use of the product implementing the present invention. In this embodiment, the up and down direction is the direction perpendicular to the mounting substrate when the coil component is mounted on the mounting substrate, or the direction perpendicular to the surface of the coil component that is parallel to the mounting substrate (mounting surface). The direction perpendicular to the up and down direction is sometimes called the lateral direction. The front-back direction and the left-right direction are one of the lateral directions and are perpendicular to each other. Furthermore, the term "plane" in this invention means a shape that is physically formed with a plane as the target, and it is not necessary for it to be a geometrically perfect plane.

[0013] <First Embodiment> (Method for Manufacturing Coil Components) Figure 1 is a perspective view showing an example of a coil component 1 manufactured by a method for manufacturing a coil component 1 according to the first embodiment of the present invention (hereinafter sometimes referred to as the manufacturing method or this method).

[0014] First, an overview of this method of this embodiment will be described. This method is a method for manufacturing a coil component 1. The coil component 1 comprises a coil 10, a case 20, and a core molded body 30. The case 20 has a bottomed housing recess 22 for housing the coil 10. The core molded body 30 contains magnetic powder and is placed in the housing recess 22. This method includes a coil housing step, a pre-molding step, a placement step, and a curing step. In the coil housing step, the coil 10 is housed in the housing recess 22. In the pre-molding step, a kneaded material, which is a mixture of thermosetting resin and magnetic powder, is molded into a pre-molded body 40 having a predetermined shape. In the placement step, one or more pre-molded bodies 40 are placed in the housing recess 22 of the case 20. In the curing step, the pre-molded bodies 40 placed in the housing recess 22 are pressurized and heated to cure them, thereby forming the core molded body 30. The predetermined shape of the temporary molded body 40 is such that it conforms to the gap 24, which is at least a part of the space inside the housing recess 22 where the coil 10 is housed during the coil housing process. During the placement process, the temporary molded body 40 is placed in the gap 24. As described above, by molding the temporary molded body to conform to the gap inside the case and then placing the temporary molded body in the gap inside the case, the gap inside the case is well filled with the temporary molded body, and the core is well filled inside the case. Furthermore, because the temporary molded body is pre-molded to conform to the gap inside the case, the temporary molded body does not need to have high fluidity compared to the case where magnetic powder and resin mixing material are introduced into the case and the mixing material is distributed to the gap inside the case. Therefore, as will be described later, the amount of solvent added to the temporary molded body can be reduced or eliminated, thereby suppressing a decrease in magnetic properties.

[0015] First, an overview of the coil component 1 manufactured in this embodiment will be described. The coil component 1 is a component having a coil 10. It is an electronic component. An electronic component is a component that can constitute part of an electronic circuit. Examples of coil component 1 include transformers, antennas, or inductors. In this embodiment, the coil component 1 is an inductor. In this embodiment, the coil component 1 is mounted on a mounting substrate (not shown) so that the mounting portion of the terminal 50 (lower surface of the terminal 50), which will be described later, is in contact with the substrate.

[0016] The coil 10 shown in Figure 2 includes a component formed of a conductive material and is a component that generates magnetic properties. The coil 10 may include not only a component formed of a conductive material (coil body 12) but also accessories attached to the component (coil body 12). In this embodiment, the coil 10 includes the coil body 12 and a bobbin 14 attached to the coil body 12. Alternatively, the coil 10 may not have a bobbin 14 and may include only the coil body 12.

[0017] The coil body 12 is made of a conductive material. As shown in Figure 4, the coil body 12 (coil 10) in this embodiment is made of a conductive material such as metal that is formed in a spiral shape. In other words, the conductive material forms one or more loops. Specifically, the coil body 12 in this embodiment has a winding portion in which the conductive material is formed in a spiral shape with respect to a predetermined axial direction (also called the spiral axis direction). In this embodiment, the axial direction of the coil body 12 is the vertical direction. The coil body 12 also has a lead-out portion 12a. The lead-out portion 12a in this embodiment is one end of the conductive material that has been drawn out from the winding portion. In this embodiment, both ends of the conductive material are drawn out from the winding portion as lead-out portions 12a.

[0018] The bobbin 14 is a component attached to the coil body 12. The bobbin 14 is attached to at least a part of the coil body 12 by engaging with or being in close contact with it. In this embodiment, the bobbin 14 is made of a non-conductive material (insulating material) such as resin. In this embodiment, the bobbin 14 covers a part of the coil body 12 (winding part) so as to enclose the winding part. In other words, a part of the coil body 12 is embedded in the bobbin 14. The lead-out portion 12a (especially its tip) is exposed from the bobbin 14 and is connected to a terminal 50, which will be described later.

[0019] In this embodiment, a portion of the bobbin 14 has a plate-like portion that extends upright relative to the mounting substrate (not shown). This plate-like portion is inserted into a notch 26 of the case 20, which will be described later, and forms part of the wall of the case 20.

[0020] The case 20 is a component that houses the coil 10. The case 20 houses at least a portion of the coil 10. In this embodiment, the case 20 houses the entire coil 10. In this embodiment, the case 20 is made of metal, but it may be made of other materials such as resin. The case 20 has a housing recess 22 that houses at least a portion of the coil 10. The housing recess 22 is a portion of the case 20 that forms an internal space that houses at least a portion of the coil 10. The internal space of the housing recess 22 is defined by a wall that surrounds the bottom and at least a portion of the sides. In this embodiment, the internal space of the housing recess 22 is defined by a wall that surrounds the bottom and the entire sides. In other words, the case 20 is open at the top and closed at the bottom and sides. In this embodiment, a notch 26, described later, is formed in a part of the wall of the case 20. This notch 26 is closed by the plate-like portion of the bobbin 14, and the internal space of the housing recess 22 is closed from below and to the sides by the case 20 and the plate-like portion of the bobbin 14. Alternatively, the internal space may be partially open to the sides. In other words, a part of the internal space on the sides does not have to be covered by the wall of the case 20 or by a part (plate-like portion) of the bobbin 14.

[0021] As shown in Figure 2, in this embodiment, a notch 26 is formed in the wall of the case 20. Specifically, a notch 26 is formed in the wall that covers the front side of the internal space of the housing recess 22, and is cut out so as to be recessed downward from the upper edge of the wall. In this embodiment, the notch 26 is formed in a rectangular shape, and a plate-shaped portion of the bobbin 14, which is also formed in a rectangular shape, is inserted into the notch 26. A part of the wall that forms the notch 26 is engaged with the plate-shaped portion of the bobbin 14.

[0022] The core molded body 30 is a component that is positioned on the inner diameter side, the outer diameter side, or both sides of the coil. In this embodiment, the core molded body 30 is positioned in the space on the inner diameter side of the coil 10. In other words, the core molded body 30 in this embodiment is inserted into the inner diameter side of the coil 10. Alternatively, the core molded body 30 may be positioned on the outer diameter side of the coil 10 so as to cover the circumferential surface of the coil 10. The core molded body 30 in this embodiment is formed by curing a temporary molded body 40, which will be described later.

[0023] The core molded body 30 contains magnetic powder and resin. Specifically, the magnetic powder in this embodiment is iron powder, but the magnetic powder may be made of other materials instead. The resin in this embodiment is a thermosetting resin. Examples of thermosetting resins include epoxy resin and phenolic resin. The core molded body 30 is formed by kneading a group of materials including magnetic powder and resin, molding a temporary molded body 40, and then curing it, as will be described later.

[0024] The magnetic powder in this embodiment includes two types of magnetic powder: large-diameter magnetic powder (referred to as large-diameter powder) and small-diameter magnetic powder (referred to as small-diameter powder). Here, the particle size of the magnetic powder is determined from the major axis (Ferret diameter) of the particles (magnetic powder particles) observed in the cross-section of the core molded body 30. Large-diameter powder is magnetic powder having a particle size greater than or equal to a predetermined value (boundary value), and small-diameter powder is magnetic powder having a particle size less than a predetermined value (boundary value). Here, the boundary value between large-diameter particles and small-diameter particles is the median value between the maximum and minimum diameters of the particles observed in the cross-section of the core molded body 30. In this embodiment, the predetermined value is 30 μm. In this embodiment, the maximum particle size of the large-diameter powder is 70.0 μm, preferably 60.0 μm. In this embodiment, the minimum particle size of the large-diameter powder is 30.0 μm, preferably 40.0 μm. Furthermore, in this embodiment, the maximum particle size of the small-diameter powder is smaller than the minimum particle size of the large-diameter powder and is 30.0 μm, preferably 15.0 μm. In this embodiment, the minimum particle size of the small-diameter powder is 3.0 μm, preferably 5.0 μm. In this embodiment, the mass of the large-diameter powder contained in the core molded body 30 (provisional molded body 40) is greater than the mass of the small-diameter powder contained in the core molded body 30. In other words, it is preferable that the proportion of large-diameter powder contained in the core molded body 30 (provisional molded body 40) is greater than the proportion of small-diameter powder contained in the core molded body 30 (provisional molded body 40).

[0025] In this embodiment, the minimum value of the magnetic powder content in the core molded body 30 (pre-molded body 40) is preferably 85.0% by mass, more preferably 90.0% by mass, and still more preferably 93.0% by mass. The maximum value of the magnetic powder content in the core molded body 30 (pre-molded body 40) is preferably 99.0% by mass, more preferably 97.0% by mass, and still more preferably 95.0% by mass. In addition, in this embodiment, the minimum value of the large-diameter powder content in the core molded body 30 (pre-molded body 40) is preferably 65.0% by mass, more preferably 70.0% by mass, and still more preferably 75.0% by mass. In this embodiment, the maximum value of the large-diameter powder content in the core molded body 30 (pre-molded body 40) is preferably 94.0% by mass, more preferably 85.0% by mass, and still more preferably 80.0% by mass. Furthermore, in this embodiment, the minimum content of small-diameter powder in the core molded body 30 (temporary molded body 40) is preferably 5.0% by mass, more preferably 10.0% by mass, and even more preferably 13.0% by mass. In this embodiment, the maximum content of small-diameter powder in the core molded body 30 (temporary molded body 40) is preferably 34.0% by mass, more preferably 25.0% by mass, and even more preferably 20.0% by mass.

[0026] In this embodiment, the minimum resin content in the core molded body 30 (temporary molded body 40) is 1.0% by mass, preferably 2.5% by mass, and more preferably 3.0% by mass. In this embodiment, the maximum resin content in the core molded body 30 (temporary molded body 40) is 10.0% by mass, preferably 5.0% by mass, and more preferably 4.0% by mass.

[0027] The core molded body 30 (provisional molded body 40, described later) in this embodiment may contain other materials in addition to magnetic powder and resin. The core molded body 30 in this embodiment may also contain a curing agent added to cure the resin. Examples of curing agents include acid anhydrides such as hexamethylenetetramine and phthalic anhydride, or polyamines such as diethylenetriamine. The content of the curing agent in the core molded body 30 (provisional molded body 40) is preferably 0.0% by mass or more and less than 5.0% by mass. Furthermore, the core molded body 30 in this embodiment may also contain a reinforcing agent to improve the mechanical strength of the core molded body 30. Examples of reinforcing agents include glass fibers, silica, or carbon fibers. The content of the reinforcing agent in the core molded body 30 (provisional molded body 40) is preferably 0.0% by mass or more and less than 5.0% by mass. Furthermore, the core molded body 30 in this embodiment may also contain a dispersant to uniformly disperse the magnetic powder and to mix the magnetic powder and resin well. Examples of dispersing agents include fatty acids, polyol esters, or silicone-based additives. Preferably, the dispersant content in the core molded body 30 (provisional molded body 40) is 0.0% by mass or more and less than 3.0% by mass. Alternatively, the core molded body 30 (provisional molded body 40) may contain only one or two of the curing agent, reinforcing agent, or dispersant, or it may contain none of them.

[0028] The core molded body 30 of this embodiment substantially does not contain a solvent for increasing the fluidity of the resin and magnetic powder mixture before curing. Examples of solvents include volatile organic solvents such as acetone. In other words, the core molded body 30 of this embodiment consists only of magnetic powder, resin, curing agent, reinforcing agent, and dispersant.

[0029] As shown in Figure 2, the coil component 1 may have a separate core 60 in addition to the core molded body 30. The core 60, which is different from the core molded body 30, is manufactured in a different manner than the core molded body 30. Specifically, in this embodiment, the core 60, which is different from the core molded body 30, is formed by molding and curing outside the case 20. In other words, the core 60, which is different from the core molded body 30, is housed or placed in the case 20 after curing. In this embodiment, the coil component 1 has a second core 62 and a third core 64 as cores 60 different from the core molded body 30. In this embodiment, the second core 62 and the third core 64 enclose the coil 10. The second core 62 and the third core 64 together with the core molded body 30 form a closed magnetic circuit. Specifically, the third core 64 has a recess that is recessed downwards, and the coil 10 is housed in this recess. In other words, the third core 64 covers the lower end face and the circumferential surface of the coil 10. The second core 62 is a plate-shaped core and is placed on top of the coil 10. In other words, the second core 62 covers the upper end face of the coil 10. As shown in Figure 4, in this embodiment, the second core 62 is placed on the third core 64, and the upper end face of the third core 64 is in contact with the lower surface of the second core 62. On the other hand, the upper surface of the core molded body 30 (core upper surface 30a) is spaced apart from the lower surface of the second core 62, and a gap exists between the upper surface of the core molded body 30 and the lower surface of the second core 62.

[0030] In this embodiment, the coil component 1 has one or more terminals 50 that are electrically connected to the coil 10 (lead-out portion 12a). In this embodiment, the coil component 1 has two terminals 50. The terminals 50 are made of a conductive material such as metal. In this embodiment, the lead-out portion 12a (particularly its tip) is inserted into a through hole formed in the plate-shaped terminal 50 and is electrically connected to the terminal 50 by direct or indirect contact. The lead-out portion 12a may be soldered to the terminal 50 or welded. In this embodiment, the terminal 50 is attached to the case 20. Specifically, the terminal 50 is fixed to the case 20 by screws or the like. More specifically, a part of the terminal 50 extends along the wall of the case 20, and this part along the wall of the case 20 is screwed to the wall of the case 20. A part of the terminal 50 is bent, and one end of the terminal 50 extends laterally along a mounting substrate (not shown). The coil component 1 is mounted on the mounting substrate by the surface contact of one end (particularly its lower surface) with the mounting substrate. As described above, the terminal 50 in this embodiment is a surface-mount terminal, but instead of this embodiment, the terminal 50 may be a pin-shaped terminal.

[0031] Next, the method of this embodiment will be described in detail. As described above, the method includes a coil housing step, a pre-forming step, a placement step, and a curing step. In the coil housing step, at least a portion of the coil 10 is housed in the housing recess 22. In this embodiment, the coil 10 is placed inside the case 20 from above. More specifically, a third core 64 is placed on the bottom of the case 20, and then the coil 10 is placed on the third core 64.

[0032] In the preliminary molding process, the kneaded material, which is a mixture of resin and magnetic powder, is molded into a predetermined shape. This predetermined shape is such that it conforms to the gap 24, which is at least a part of the space inside the housing recess 22 in which the coil 10 is housed in the coil housing process. The kneaded material contains at least resin and magnetic powder, and may also contain other materials such as the curing agent, reinforcing agent and dispersant mentioned above.

[0033] The gap 24 is a space inside the housing recess 22, and is a void partially defined by a tangible member such as the case 20 (its wall or bottom), the coil 10, or another core 60 other than the core molded body 30. In other words, at least a portion of the gap 24 is defined by a tangible member, and the other portion of the gap 24 may not be defined by such other member. Preferably, at least a portion of the lower surface and side surface of the gap 24 is defined by a tangible member. More preferably, the entire lower surface and side surface of the gap 24 is defined by a tangible member. The other member defining the gap 24 may be any member of the coil component 1 other than the core molded body 30 (temporary molded body 40). As shown in Figure 3, the gap 24 in this embodiment is a void on the inner diameter side of the coil 10. Specifically, the side of the gap 24 is defined by the inner circumferential surface of the coil 10 (the surface facing the inner diameter side in the coil 10). Furthermore, the area below the gap 24 is defined by the third core 64. Alternatively, the gap 24 may be a space defined by any or all of the following: the surface of the coil 10 (circumferential or inner circumferential surface, etc.), the surface of the case 20 (particularly the wall or bottom), or the surface of the other core 60. For example, in the third or fourth embodiment described later, the gap 24 is defined by the circumferential surface of the coil 10, the wall of the case 20, and the surface of the core 60.

[0034] The formation of the temporary molded body 40 in a shape that follows the gap 24 means that at least a part of the shape of the temporary molded body 40 substantially matches the shape of the surface of the member defining the gap 24. In other words, when the temporary molded body 40 is placed in the receiving recess 22 (gap 24) in the placement process described later, the surface of the temporary molded body 40 contacts or is close to the surface of the member defining the gap. Only one temporary molded body 40 may be molded for a single core molded body 30, or multiple temporary molded bodies 40 may be molded. If multiple temporary molded bodies 40 are molded, it is sufficient that a part of the shape of each temporary molded body 40 substantially matches the shape of the surface of the member defining the gap 24.

[0035] In this embodiment, the temporary body 40 is formed by pushing the kneading material from above into a mold that penetrates vertically. For example, the mold in this embodiment has a cylindrical shape with the same diameter as the inner diameter of the coil. The kneading material coming out from the bottom of the mold is cut to a predetermined thickness (dimension in the vertical direction), thereby forming the temporary body 40 to a desired thickness. In this embodiment, the predetermined thickness is smaller than the dimension of the coil 10 in the axial direction. Alternatively, the predetermined thickness may be the same as the dimension of the coil 10 in the axial direction, or it may be larger than that dimension. Some of the temporary bodies 40 (temporary body 40b) in the third or fourth embodiment described later may also be formed by the method described above. Alternatively, the temporary body 40 may be formed by pushing the kneading material into a mold having a bottomed recess. Or, the temporary body 40 may be formed into a desired shape by first forming it into a predetermined shape using a mold or the like, and then removing a part of it, such as by hollowing it out. For example, some of the temporary molded bodies 40 (temporary molded bodies 40a) in the third or fourth embodiment described later may be formed by creating a recess on the lower surface of a kneaded material that has been formed into a plate shape.

[0036] The mixing process, which involves kneading the resin, magnetic powder, and other materials (collectively referred to as the material group), is performed before the preliminary molding process. During the mixing process, the material group may be kneaded in a manner that includes gas (air). For example, the mixing process of the material group may be carried out in an environment where sufficient air is present around the material group. More specifically, the material group may be kneaded in a way that folds the putty-like material group so that air is sandwiched between the material groups.

[0037] In the placement process, one or more temporary molded bodies 40 are placed in the housing recess 22 of the case 20. More specifically, one or more temporary molded bodies 40 are placed in the gap 24. At this time, the temporary molded bodies 40 are placed in the gap 24 such that at least a portion of their surface is aligned with the surface of the member that defines the gap 24. In this embodiment, one temporary molded body 40 is placed in the gap 24 such that its lower surface contacts the upper surface (bottom surface of the recess) of the third core 64, and its side surface is aligned with the inner circumferential surface of the coil 10.

[0038] The placement process may be performed immediately following the pre-forming process. Specifically, if the pre-formed body 40 is formed in the pre-forming process by pushing a kneading material from above into a mold that penetrates vertically, the coil component 1 (receiving recess 22) may be placed below the mold so that the pre-formed body 40 extruded from the mold is placed in the receiving recess 22. More specifically, with the coil component 1 positioned below the mold such that a gap 24 is located directly below the mold, the kneading material is pushed into the mold. The kneading material extruded from below the mold is cut to a predetermined thickness and separated from the mold as the pre-formed body 40. The separated pre-formed body 40 falls into the gap 24 located directly below the mold and is placed there. Alternatively, the pre-formed body 40, which has been formed in a location other than where the placement process is performed, may be transported to the location where the placement process is performed, and the pre-formed body 40 may be placed in the receiving recess 22 of the coil component 1.

[0039] In the curing process, the temporary molded body 40 is pressurized and heated to cure the resin inside the temporary molded body 40, thereby forming the core molded body 30. The pressurization and heating of the temporary molded body 40 may be performed simultaneously, or the heating may be performed after the pressurization of the temporary molded body 40. In this embodiment, the pressurization of the temporary molded body 40 is performed by pressing a jig against the temporary molded body 40 from above. In this embodiment, the surface of the temporary molded body 40, which is placed in the gap 24 in the placement process, is spaced apart from the surfaces of other members that define the gap 24. In particular, the side surface of the temporary molded body 40 is spaced apart from the surfaces of other members that define the sides of the gap 24. Specifically, in this embodiment, the side surface of the temporary molded body 40 is spaced apart from the inner circumferential surface of the coil 10. When the temporary molded body 40 is pressurized from above, the temporary molded body 40 deforms slightly, and the temporary molded body 40 comes into close contact with the other surfaces that define the gap 24.

[0040] In this embodiment, the second core 62 is placed above the coil 10 after the curing process or during the curing process, and the coil component 1 is manufactured. Furthermore, at any time after the coil 10 is placed inside the case 20, the terminal 50 is attached to the case 20 so as to be electrically connected to the lead-out portion 12a.

[0041] (Coil component) Next, the detailed structure of the coil component 1 of this embodiment will be described. Figure 6(a) is an example of a cross-section of a core (the target core described later) manufactured to resemble the core molded body 30 of this embodiment. Figure 6(b) is an example of a cross-section of a comparison core (the comparison core described later) described later.

[0042] First, an overview of the coil component 1 will be described. As described above, the coil component 1 comprises a coil 10, a case 20 having a bottomed housing recess 22 for housing the coil 10, and a core molded body 30 containing resin and magnetic powder, which is disposed in the housing recess 22. In this embodiment, as shown in Figure 6(a), the core molded body 30 contains voids 32 inside. The porosity, which is the ratio of the volume of voids 32 to the envelope volume (apparent volume) of the core molded body 30, is 35.0% or more. Preferably, the porosity is 40.0% or more, and more preferably 43.0% or more. By having a porosity of 35.0% or more, the magnetic properties (especially the inductance) of the coil component 1 can be kept good. Specifically, in a core molded body 30 containing a predetermined amount of magnetic powder in a predetermined volume, the inclusion of voids in a proportion greater than the above-mentioned ratio increases the mass of magnetic powder per unit volume in the portion of the core molded body 30 other than the voids (the portion composed of a mixture of magnetic powder, resin, and other materials such as a curing agent; also referred to as the filling portion 32a). As a result, magnetic flux can pass through the filling portion 32a smoothly, and the magnetic properties of the coil component 1 are maintained well. Furthermore, as described above, the inclusion of voids 32 in the core molded body 30 in a proportion greater than the predetermined ratio ensures that the external shape of the coil component 1 (especially the core molded body 30) is stably maintained even after the curing process. This is because, even when the resin contained in the core molded body 30 (temporary molded body 40) hardens due to crosslinking polymerization caused by heating of the temporary molded body 40 during the curing process, the inclusion of voids in the core molded body 30 reduces the volume change of the core molded body 30 due to the crosslinking polymerization. In particular, in this embodiment, as described above, the kneading material forming the temporary molded body 40 substantially does not contain solvent, and the voids 32 in the core molded body 30 are not filled with solvent. Therefore, in this embodiment, in which the kneading material substantially does not contain a solvent, the external shape of the coil component 1 is maintained more stably.

[0043] The void 32 is a void portion within the envelope volume of the core molded body 30 where magnetic powder, resin, etc. (kneaded material) are not filled. That is, the void 32 is a void portion defined by the kneaded material. In other words, the kneaded material, including the solvent, is not filled in the void 32. Fig. 6(a) is a cross-section of the core molded body 30, and the black portion in this cross-section is the void 32. In order to suppress the deterioration of the magnetic characteristics of the coil component 1, it is preferable that the porosity is less than 55.0%. More preferably, the porosity is less than 50.0%.

[0044] In the present embodiment, the porosity of the core molded body 30 is within the above-mentioned range depending on any one or more, or all of the shape of the magnetic powder, the composition of the magnetic powder, or the kneading conditions of the kneaded material. Specifically, first, as described above, the magnetic powder in the present embodiment includes both large-diameter powder and small-diameter powder. By having a part of the magnetic powder with a large diameter, voids 32 can be generated between the aggregated large-diameter powders. Also, by having a part of the magnetic powder with a small diameter, the large-diameter powders can be well aggregated by the resin and the small-diameter powders. Second, in the present embodiment, the content ratio of the large-diameter powder contained in the core molded body 30 (preform 40) is larger than the content ratio of the small-diameter powder contained in the core molded body 30 (preform 40). Thereby, voids 32 are formed better inside the core molded body 30. Third, in the kneading process of the present embodiment, the material group containing resin and magnetic powder is kneaded so as to contain gas (air). Thereby, voids 32 are formed well inside the preform 40, and the voids 32 are retained inside the core molded body 30 even after the curing process.

[0045] The porosity in the core molded body 30 is calculated from the cross-section of the core molded body 30. Specifically, as shown in Figure 6(a), an image of the cross-section of the core molded body 30 is obtained, and the porosity is calculated by determining the ratio of the total area of ​​voids 32 to the total area of ​​the image. Figure 6(a) is a cross-section of a core (referred to as the target core) manufactured to resemble the core molded body 30 in this embodiment. The target core was manufactured by pressurizing and heating the temporary molded body 40 without placing it inside the case 20. That is, the target core was manufactured by pressurizing and heating the temporary molded body 40 alone. The minimum porosity of the multiple target cores manufactured was 36.6%, and the maximum was 49.9%. The average porosity of the multiple target cores was 44.5%.

[0046] As shown in Figure 6(a), it is preferable that the void 32 in this embodiment has a width dimension of 30.0 μm or more. In other words, it is preferable that at least a portion of the void 32 has a width dimension of 30.0 μm or more. More preferably, at least a portion of the void 32 has a width dimension of 50.0 μm or more. By having a sufficiently large void 32 in this way, the filling portion 32a containing the magnetic powder and resin does not become small in diameter. In other words, the filling portion 32a is contained inside the core molded body 30 as a large mass. This allows the magnetic flux to pass through the filling portion 32a stably.

[0047] Figure 6(b) shows a cross-section of a comparative core (referred to as the comparative core) manufactured by filling a mixture of magnetic powder and resin with a volatile organic solvent to give it fluidity into a mold, and then curing it by pressurizing and heating. As shown in Figure 6(b), although localized voids 32 were sometimes observed in the cross-section of the comparative core, voids 32 were hardly observed.

[0048] Figure 7(a) shows the upper surface of the target core. Figure 7(c) shows the upper surface of the comparison core. In this embodiment, a plurality of recesses 34 with an opening diameter of 10.0 μm or more are formed on the upper surface of the core molded body 30 (the upper core surface 30a shown in Figure 2). In this embodiment, the boundary value between large-diameter particles and small-diameter particles is about 30 μm. In other words, a plurality of recesses 34 with an opening diameter of one-third or more of the boundary value between large-diameter particles and small-diameter particles are formed on the upper surface of the core molded body 30. Also, in this embodiment, the average particle size of the small-diameter particles is about 10.0 μm. In other words, a plurality of recesses 34 with an opening diameter equal to or greater than the average particle size of the small-diameter particles are formed on the upper surface of the core molded body 30. In this embodiment, the occupancy rate (hereinafter referred to as the recess occupancy rate), which is the ratio of the area occupied by the plurality of recesses 34 on the upper core surface 30a (see Figure 2), is less than 8.0%. Preferably, the recess occupancy rate is less than 5.0%. The recess occupancy rate is 0.0% or more. In other words, instead of this embodiment, the recess 34 does not have to be substantially formed on the upper surface of the core molded body 30. By having a recess occupancy rate of less than 8.0%, the magnetic properties (especially the inductance) of the coil component 1 can be kept good. Specifically, recesses 34 of a predetermined size corresponding to the particle size of the magnetic powder may be formed on the upper surface of the core molded body 30. Because large recesses 34 of a predetermined size or larger than described above are not formed on the upper surface of the core molded body 30 in a predetermined proportion or more, the upper surface of the core molded body 30 can be in contact with other cores 60 (second core 62 in this embodiment) placed on the core molded body 30 as a whole, or can be separated from the other cores 60 at a certain distance. As a result, the cores make good surface contact with each other, or the gap length between the cores is kept constant at all parts, so that the magnetic properties of the coil component 1 are kept good. As in this embodiment, by keeping the void ratio inside the core molded body 30 above a predetermined value, while keeping the recess occupancy rate below a predetermined value, the magnetic properties of the coil component 1 are maintained more favorably. Alternatively, because the upper surface (core upper surface 30a) of the core molded body 30 is flat, the magnetic flux emanating upward from the upper surface tends to align in a direction perpendicular to the upper surface.This suppresses the loss of magnetic flux directed upward from the core molded body 30, and the magnetic flux exiting the core molded body 30 favorably heads toward the second core 62.

[0049] The recess 34 is a recess formed to be recessed downward on the upper surface of the core molded body 30. The shape of the recess 34 in plan view is substantially circular (including an elliptical shape), but may be an irregular shape. The depth of the recess 34 in the present embodiment is 1.0 μm or more, but may be less than 1.0 μm. The opening diameter of the recess 34 is the largest dimension among the dimensions of the recess 34 in the direction orthogonal to the depth direction (vertical direction) of the recess 34. For example, when the shape of the recess 34 is substantially elliptical, the opening diameter of the recess 34 is the major axis of the ellipse.

[0050] In the present embodiment, the recess occupancy rate is within the above-described range by any one or all of the molding conditions of the core molded body 30 or the post-molding treatment of the core molded body 30. Specifically, in the present embodiment, by leveling the upper surface of the preform 40 in the molding process, the recess occupancy rate may be set to a predetermined value or less. For example, the upper surface of the preform 40 may be leveled by a jig. Alternatively, when the kneaded material is pushed into a mold and the kneaded material extruded from the mold is cut, the upper surface of the preform 40 may be leveled by moving a cutting jig (such as a blade) in a certain direction (one of the lateral directions) with respect to the kneaded material to cut the kneaded material. Alternatively, the recess occupancy rate may be set to a predetermined value or less by performing a post-treatment such as polishing the upper surface of the cured core molded body 30 with a file or the like.

[0051] Figure 7(c) shows the upper surface of the comparison core. As shown in Figure 7(c), numerous recesses 34 with an opening diameter of 10.0 μm or more are formed on almost the entire upper surface of the comparison core. In Figure 7(c), only a portion of the relevant recesses 34 are shown with dotted lines. Figure 7(b) is a magnified view of region VIIb in Figure 7(a). As shown in Figure 7(b), a small number of recesses 34 with an opening diameter of 10.0 μm or more are formed on the upper surface of the target core. However, as shown in Figure 7(a), when the entire upper surface of the target core is observed, recesses 34 with an opening diameter of 10.0 μm or more are almost nonexistent, or recesses 34 with an opening diameter of less than 10.0 μm are predominantly formed.

[0052] The recess occupancy rate is calculated by acquiring an image of the upper surface of the core molded body 30 and determining the ratio of the total area of ​​recesses 34 with an opening diameter of a predetermined size (10.0 μm in this embodiment) or larger to the total area of ​​the image. When calculating the recess occupancy rate, the shape of the recesses 34 may be approximated as circular (including elliptical) to calculate the area of ​​the recesses 34. The average recess occupancy rate in the comparison core was 8.6%. In contrast, the recess occupancy rate in the target core was less than 3.0%, and more specifically, substantially no recesses 34 with an opening diameter of 10.0 μm or larger were observed on the upper surface of the target core.

[0053] As described above, in this embodiment, the coil 10 is formed in a spiral shape, and the core molded body 30 is arranged in the space on the inner diameter side of the coil 10. In this embodiment, as shown in Figure 5(a), the core molded body 30 is arranged inward from the end face 10a (upper end face) of the coil 10 in the spiral axis direction (axial direction). In other words, the upper end of the core molded body 30 (the upper end of the outer edge portion 36b, which will be described later in this embodiment) is arranged inward in the axial direction from the end face 10a of the coil 10 (the inner side of the coil 10 in the axial direction; the lower side in the figure). The end portion 36 of the core molded body 30 in the spiral axis direction includes the inner edge portion 36a and the outer edge portion 36b. Here, the end portion 36 of the core molded body 30 in the spiral axis direction is the end on the side where the case 20 is open in the spiral axis direction. In this embodiment, the end portion 36 of the core molded body 30 in the spiral axis direction is the upper end of the core molded body 30 in the figure. The inner edge portion 36a is a part of the inner side of the coil 10 in the radial direction at that end. The outer edge portion 36b is a part of the end that is radially outside of the inner edge portion 36a. In other words, when the end portion 36 of the core molded body 30 is viewed in the direction of the helical axis (especially when viewed from above), the central part of the end portion 36 in the radial direction of the coil 10 is the inner edge portion 36a. Also, the part of the end portion 36 that encircles the inner edge portion 36a is the outer edge portion 36b. That is, the periphery of the end portion 36 and a part adjacent to that periphery are the outer edge portion 36b.

[0054] In this embodiment, as shown in Figure 5(a), the outer edge portion 36b protrudes more in the direction of the helical axis than the inner edge portion 36a. Specifically, the outer edge portion 36b protrudes more outward from the coil 10 in the direction of the helical axis than the inner edge portion 36a (upward in this embodiment). Note that in Figure 5(a), the amount of protrusion of the outer edge portion 36b is greatly exaggerated for convenience. In other words, as shown in Figure 5(a), a recess that is recessed downward is formed in the central part (inner edge portion 36a) of the upper end surface of the core molded body 30. The outer edge portion 36b, which is the opening of this recess, extends in the circumferential direction of the coil 10 along the inner circumferential surface of the coil 10. In order to make the outer edge portion 36b protrude more than the inner edge portion 36a in the direction of the helical axis, the temporary molded body 40 may be formed in the temporary molding process by applying a sufficient amount of kneading material to the outer edge portion 36b so that the outer edge portion 36b protrudes more than the inner edge portion 36a in the direction of the helical axis. Alternatively, in the hardening process, the temporary molded body 40 may be pressed using a jig having a diameter smaller than the inner diameter of the coil 10.

[0055] As described above, the fact that the outer edge portion 36b protrudes in the direction of the helical axis makes it easy to separate the coil 10 and the core molded body 30 from each other when discarding the coil component 1. Specifically, when discarding the coil component 1, it is sometimes desirable to separate the coil 10, which contains metal, from the core molded body 30 from the perspective of processing or recycling the material of the coil component 1. However, since the core molded body 30 is molded under pressure while positioned on the inner diameter side of the coil 10, it is in close contact with the inner circumferential surface of the coil 10, and it may be difficult to separate the coil 10 from the core molded body 30. In this case, because the outer edge portion 36b protrudes in the direction of the helical axis, it becomes easy to separate the core molded body 30 from the coil 10 by scraping the outer edge portion 36b with a needle-shaped jig or the like, starting from the outer edge portion 36b. In addition, because the inner edge portion 36a is recessed relative to the outer edge portion 36b, the temporary molded body 40 can be sufficiently pressurized during the hardening process. Therefore, sufficient strength can be given to the core molded body 30, and the core molded body 30 can be sufficiently adhered to the coil 10. In this way, while forming a core molded body 30 that is sufficiently pressurized to have high strength and adhere well to the coil 10, the core molded body 30 can be easily separated from the coil 10. Furthermore, as described above, because the outer edge portion 36b protrudes in the direction of the helical axis, the magnetic flux emanating upward from the upper end face (core upper surface 30a) of the core molded body 30 can be well focused and directed toward the second core 62. Specifically, the magnetic flux emanating upward from the outer edge portion 36b is directed toward the second core 62 in a direction that is slightly inclined inward in the radial direction of the coil 10 with respect to the vertical direction. Therefore, the magnetic flux emanating upward from the core upper surface 30a of the core molded body 30 can be directed toward the second core 62 without diffusion.

[0056] In this embodiment, the void ratio at the outer edge 36b is smaller than that at the inner edge 36a. Therefore, the inner edge 36a is more brittle than the outer edge 36b, or in other words, the outer edge 36b has greater rigidity than the inner edge 36a. As a result, when the outer edge 36b is scraped with a needle-shaped tool or the like to separate the core molded body 30 from the coil 10 during the disposal of the coil component 1, or when the outer edge 36b is pushed toward the inner edge 36a, the outer edge 36b can break the inner edge 36a so that it embeds itself well into the inner edge 36a. This makes it easy to break the core molded body 30 starting from the outer edge 36b and separate the core molded body 30 from the coil 10.

[0057] Alternatively, the void ratio at the outer edge 36b may be greater than that at the inner edge 36a. This makes the outer edge 36b more brittle and easily broken than the inner edge 36a. Therefore, when the outer edge 36b is scraped with a needle-shaped tool or the like to separate the core molded body 30 from the coil 10 during the disposal of the coil component 1, the outer edge 36b is easily broken. As a result, cracks and the like spread from the broken outer edge 36b to the inner edge 36a, allowing the entire core molded body 30, including the inner edge 36a, to be easily broken and separated from the coil 10.

[0058] Alternatively, as shown in Figure 4, the upper surface of the core molded body 30 (core upper surface 30a) may be flush with the upper end surface (end surface 10a) of the coil 10.

[0059] <Second Embodiment> Figure 5(b) is a perspective view showing an example of the coil component 1 according to this embodiment. First, an overview of the coil component 1 of this embodiment will be described.

[0060] (Coil component) Similar to the first embodiment, the coil 10 of this embodiment is formed in a helical shape. A core molded body 30 is arranged in the space on the inner diameter side of the coil 10. The core molded body of this embodiment differs from that of the first embodiment in that it protrudes beyond the end face of the coil in the direction of the helical axis and covers a part of the end face of the coil.

[0061] Next, the coil component 1 of this embodiment will be described in detail. More specifically, in the helical axis direction (vertical direction) of the coil 10, the core molded body is formed to protrude outward from the annular end face 10a of the coil 10. Here, the annular end face 10a of the coil 10 is the end face 10a on the side where the case 20 is open in the helical axis direction (vertical direction), and is the upper end face of the coil 10 in this embodiment. Hereinafter, a part of the core molded body 30 that is located above the end face 10a of the coil 10 will be referred to as the protruding portion 38. In this embodiment, a part of the core molded body 30 that protrudes in the helical axis direction (the covering portion 31 of the protruding portion 38) covers the inner surface 10a1, which is a part of the radially inner side of the coil 10 on the annular end face 10a. The outer surface 10a2, which is a part of the radially outer side of the annular end face 10a beyond the inner surface 10a1, is exposed from the core molded body 30. The inner surface 10a1 of the annular end face 10a is the inner circumference and a portion of the surface adjacent to the inner circumference of the end face 10a. That is, the inner surface 10a1 is an annular region extending in the circumferential direction of the coil 10. The outer surface 10a2 of the annular end face 10a is an annular region located radially outward from the inner surface 10a1. In Figure 5(b), the dimensions of the covering portion 31 in the radial direction of the coil 10 and the thickness dimension (vertical dimension) of the covering portion 31 are exaggerated for convenience. Both dimensions of the covering portion 31 in the coil component 1 are smaller than those shown in Figure 5(b). With the above configuration, it becomes easy to separate the coil 10 and the core molded body 30 from each other when the coil component 1 is disposed of. Specifically, when the coil component 1 is disposed of, it becomes easy to separate the core molded body 30 from the coil 10 by scraping the covering portion 31 with a needle-shaped jig or the like.

[0062] In this embodiment, the dimensions of the area covered by the covering portion 31 on the end face 10a in the radial direction of the coil 10 (the dimensions of the inner surface 10a1 in the radial direction of the coil 10) are smaller than the dimensions of the area not covered by the covering portion 31 on the end face 10a in the radial direction of the coil 10 (the dimensions of the outer surface 10a2 in the radial direction of the coil 10). This allows the covering portion 31 to be easily peeled off and separated from the coil 10 when the coil component 1 is disposed of.

[0063] In this embodiment, the void ratio of the covering portion 31, which is a part of the core molded body 30 that covers the inner surface 10a1, is smaller than the void ratio of other parts of the core molded body 30 (for example, the main body portion 33, which will be described later). As a result, the covering portion 31 has greater rigidity than the main body portion 33, so when the covering portion 31 is scraped with a needle-shaped jig or the like when discarding the coil component 1, the core molded body 30 is more likely to break starting from the covering portion 31. For example, in this embodiment, the void ratio of the covering portion 31 is larger than the void ratio of the main body portion 33 (especially its central portion). The main body portion 33 is the part of the core molded body 30 located on the inner diameter side of the coil 10. That is, the main body portion 33 is the part of the core molded body 30 located below the end face 10a (upper end face) of the coil 10. Furthermore, the void ratio of the central portion of the protruding portion 38 (the part of the protruding portion 38 that is radially inward of the coil 10 than the covering portion 31) may be smaller than the void ratio of the main body portion 33. As a result, the entire protruding portion 38 has greater rigidity than the main body portion 33, so when the covering portion 31 is scraped with a needle-shaped jig or the like when discarding the coil component 1, the covering portion 31 is less likely to break at the base and separate from the central portion of the protruding portion 38. Therefore, the force applied to the covering portion 31 by the jig or the like is transmitted to the entire protruding portion 38, making it easier to separate the core molded body 30 from the coil 10 starting from the covering portion 31.

[0064] Alternatively, the void ratio of the covering portion 31 may be greater than that of other parts of the core molded body 30 (for example, the main body portion 33, which will be described later). This allows the covering portion 31 to be easily destroyed when the covering portion 31 is scraped with a needle-shaped tool or the like during disposal of the coil component 1, and a crack can be created in the core molded body 30 starting from the covering portion 31. As a result, the core molded body 30 can be easily destroyed and separated from the coil 10.

[0065] The coil component 1 of this embodiment has the following features, similar to those of the first embodiment. In the coil component 1 of this embodiment, the porosity, which is the ratio of the volume of voids 32 to the envelope volume of the core molded body 30, is 35% or more. In addition, in this embodiment, the recess occupancy rate is less than 8.0%. Furthermore, the coil component 1 of this embodiment is manufactured by a manufacturing method that includes a coil housing step, a pre-forming step, a placement step, and a curing step, similar to those described in the first embodiment.

[0066] <Third Embodiment> Figure 8 is a perspective view showing an example of the coil component 1 according to this embodiment, and Figure 9 is an exploded perspective view of the coil component 1. First, an overview of the coil component 1 of this embodiment will be described.

[0067] (Coil component) In the coil component of this embodiment, the porosity, which is the ratio of the volume of voids 32 to the envelope volume of the core molded body 30, is 35% or more. The coil component 1 of this embodiment differs from the first or second embodiment in that the core molded body 30 has a fragile interface portion 37.

[0068] Next, the coil component 1 of this embodiment will be described in detail. Similar to the first embodiment, the coil component 1 of this embodiment has a coil 10, a case 20, a core molded body 30, a separate core 60 different from the core molded body 30, and terminals 50.

[0069] In this embodiment, as shown in Figures 8 and 9, the core molded body 30 is positioned on the outer diameter side of the coil 10 and above the coil 10. In other words, the core molded body 30 has a bottomed recess on its lower surface that is recessed upward, and the coil 10 is housed in this recess. In this embodiment, as shown in Figure 11, a portion of the front side of the circumferential surface of the coil 10 is not covered by the core molded body 30. In other words, the core molded body 30 covers the left, right, and rear sides of the coil 10. Furthermore, in this embodiment, as shown in Figure 10, the core molded body 30 has a recess formed therein into which a column portion of another core 60, which will be described later and is different from the core molded body 30, is inserted.

[0070] The coil component 1 has a separate core 60, distinct from the core molded body 30. This separate core 60 has a plate-like portion and a columnar portion that protrudes upward from the plate-like portion. The coil 10 is placed on the plate-like portion of this separate core 60, and the lower surface of the coil 10 is covered by the plate-like portion. The columnar portion of this separate core 60 is inserted into the inner diameter side of the coil 10 and is positioned on the inner diameter side of the coil 10. Furthermore, as shown in Figure 10, in this embodiment, the columnar portion of the separate core 60, distinct from the core molded body 30, is inserted into a recess formed in a part of the core molded body 30 that is positioned above the coil 10. This separate core 60 is in contact with the inner wall and bottom surface (top surface located on the upper side in the figure) of the recess formed in the core molded body 30. The core molded body 30 and this separate core 60 form a closed magnetic path around the coil 10.

[0071] As described above, as shown in Figure 8, in this embodiment the core molded body 30 has a weak interface portion 37. Specifically, the core molded body 30 has a weak interface portion 37 (in this embodiment, a first weak interface portion 37a and a second weak interface portion 37b, which will be described later) that breaks more easily than other parts of the core molded body 30 (central portion 35) when an external force is applied to the core molded body 30. The presence of a weak interface portion 37 in the core molded body 30 makes it easier to separate the coil 10 and the core molded body 30 from each other when the coil component 1 is disposed of. Specifically, when an external force is applied to the core molded body 30 using a tool such as a hammer when the coil component 1 is disposed of, the core molded body 30 is destroyed well starting from the weak interface portion 37, making it easier to separate the coil 10 from the core molded body 30. In particular, by applying an external force to the weak interface portion 37 or its vicinity along the direction in which the weak interface portion 37 extends, the core molded body 30 can be destroyed well along the weak interface portion 37.

[0072] The weak interface portion 37 is a part of the core molded body 30 that fractures more easily than other parts (central portion 35) of the core molded body 30 when an external force is applied to the core molded body 30. The weak interface portion 37 is a planar region extending on a predetermined plane within the core molded body 30, or a region extending on a predetermined plane and having a certain thickness. The predetermined plane on which the weak interface portion 37 extends is called the weak interface. When an external force is applied to the core molded body 30, fracture easily occurs along the weak interface portion 37. For example, when an external force is applied to the core molded body 30, one or more cracks easily form along the weak interface portion 37, or the core molded body 30 easily breaks at the weak interface portion 37. The external force on the core molded body 30 may be applied to any part of the core molded body 30, but it is preferable to apply it to the weak interface portion 37 or its vicinity. More specifically, it is preferable to apply the external force to the weak interface portion 37 or its vicinity in a direction along the direction in which the weak interface extends. As described above, the fragile interface 37 may be an interface with zero thickness inside the core molded body 30. Alternatively, the fragile interface 37 may be a region with a constant thickness inside the core molded body 30. If the fragile interface 37 has a constant thickness, it is preferable that the thickness dimension (the dimension of the fragile interface 37 in a direction perpendicular to the fragile interface) is smaller than the dimension of the fragile interface 37 in a direction along the fragile interface. More preferably, it is preferable that the thickness dimension of the fragile interface 37 is smaller than the dimension of the fragile interface 37 in any direction along the fragile interface. In other words, the fragile interface 37 may be a flat, plate-like region extending over the fragile interface.

[0073] As described above, the fragile interface portion 37 is a part of the core molded body 30 that is more easily fractured than other parts of the core molded body 30 when an external force is applied to the core molded body 30. Here, other parts of the core molded body 30 refer to, for example, the central portion 35 of the core molded body 30. As shown in Figure 11, the central portion 35 is the central part of the core molded body 30 that has a certain thickness. Specifically, in this embodiment, the central portion 35 is the central part of the coil 10 that has a larger dimension than the fragile interface portion 37 (particularly the second fragile interface portion 37b) in the radial direction. More specifically, in this embodiment, the central portion 35 is a part of the core molded body 30 located at the four corners of the case 20, and is particularly its central portion.

[0074] In this embodiment, as will be described later, a fragile interface portion 37 is formed in the core molded body 30 by the molding conditions of the temporary molded body 40, the connection of multiple temporary molded bodies 40, or both. Therefore, even if the dimensions of the central portion 35 and the fragile interface portion 37 are the same in the direction in which the external force is applied, the fragile interface portion 37 will break more easily than the central portion 35. In other words, even if an external force is applied to the central portion 35 and the fragile interface portion 37 which have similar shapes and dimensions, the fragile interface portion 37 will break more easily than the central portion 35. Specifically, in this embodiment, as will be described later, the temporary molded body 40 is molded such that the porosity of the fragile interface portion 37 is greater than the porosity of the central portion 35. For example, the core molded body 30 may be molded such that the porosity of the fragile interface portion 37 is greater than the porosity of the central portion 35 by molding the temporary molded body 40 using different kneading conditions or by combining kneading materials with different particle sizes or compositions of magnetic powder. Furthermore, in this embodiment, a weak interface portion 37 is formed by manufacturing the core molded body 30 using a plurality of temporary molded bodies 40 (temporary molded bodies 40a, 40b) as described later. Specifically, in the core molded body 30, the joints of the plurality of temporary molded bodies 40, as described later, and their vicinity become the weak interface portion 37.

[0075] In this embodiment, as shown in Figure 10, the core molded body 30 has a first fragile interface portion 37a as a fragile interface portion 37. The first fragile interface portion 37a extends in a direction intersecting the depth direction (vertical direction) of the housing recess 22. Here, the extension direction of the first fragile interface portion 37a (the extension direction of the fragile interface of the first fragile interface portion 37a) is the lateral direction (front-back direction or left-right direction) which is perpendicular to the vertical direction, or a direction slightly inclined with respect to the lateral direction. In other words, the first fragile interface portion 37a extends parallel to the mounting surface of the coil component 1 (including a substantially parallel state that is slightly inclined with respect to the mounting surface). The mounting surface of the coil component 1 is the surface of the coil component 1 that extends parallel to the mounting substrate when the coil component 1 is mounted on the mounting substrate. The mounting surface of the coil component 1 is the lower surface of the case 20 or the lower surface of the terminal 50 which is a surface mount terminal. More specifically, in this embodiment, the first fragile interface 37a is the interface and its vicinity between a portion of the core molded body 30 that is located on the outer diameter side of the coil 10 and a portion of the core molded body 30 that is located above the coil 10. Furthermore, in this embodiment, in which the core molded body 30 is formed from a plurality of temporary molded bodies 40 (temporary molded bodies 40a, 40b) as will be described later, the first fragile interface 37a is formed including the boundary between the temporary molded body 40a located on the outer diameter side of the coil 10 and the temporary molded body 40b located above the coil 10.

[0076] As the first fragile interface portion 37a extends in a direction intersecting the vertical direction, when the coil component 1 is discarded, it becomes easy to separate the core molded body 30 vertically using the first fragile interface portion 37a as a starting point, and to remove at least a part of the core molded body 30 from the coil 10. In particular, when a recess is formed in the core molded body 30 as in this embodiment, and the coil 10 is placed in the recess, it becomes easy to remove the coil 10 from the core molded body 30 by separating the wall portion that forms the recess (a portion of the core molded body 30 located on the outer diameter side of the coil 10) and the bottom portion that forms the recess (a portion of the core molded body 30 located above the coil 10).

[0077] In Figure 10, the first fragile interface 37a is shown by a dotted line and is depicted as an interface with zero thickness extending in the left-right direction and the depth direction of the paper (front-back direction). As described above, the fragile interface 37 may have thickness, and the first fragile interface 37a may also be a region with thickness in the vertical direction. Similarly, in Figure 11, the second fragile interface 37b is shown by a dotted line and is depicted as an interface with zero thickness extending in the radial direction of the coil 10 and the depth direction of the paper (vertical direction). As described above, the fragile interface 37 may have thickness, and the second fragile interface 37b may also be a region with thickness in the vertical direction.

[0078] In this embodiment, the core molded body 30 has a second weak interface portion 37b as a weak interface portion 37. The second weak interface portion 37b extends along the depth direction (vertical direction) of the receiving recess 22. Specifically, the extension direction of the second weak interface portion 37b (the extension direction of the weak interface of the second weak interface portion 37b) is in the vertical direction or a diagonal direction slightly inclined with respect to the vertical direction. In this embodiment, the second weak interface portion 37b extends in both the vertical direction and the radial direction of the coil 10. Furthermore, in this embodiment in which the core molded body 30 is molded from a plurality of temporary molded bodies 40 (particularly temporary molded bodies 40b1 to 40b4) as described later, the second weak interface portion 37b is formed including the interface surfaces between the plurality of temporary molded bodies 40b1 to 40b4 arranged on the outer diameter side of the coil 10.

[0079] In this embodiment, as shown in Figure 11, the core molded body 30 has a plurality of second fragile interface portions 37b. Specifically, the plurality of second fragile interface portions 37b are formed at positions spaced apart from each other in the circumferential direction of the coil 10. More specifically, the second fragile interface portions 37b are formed in the core molded body 30 in the portions located on the left, right, and rear sides of the coil 10.

[0080] As the second fragile interface portion 37b extends along the vertical direction, when the coil component 1 is discarded, it becomes easy to break the core molded body 30 starting from the second fragile interface portion 37b and remove the core molded body 30 from the coil 10. In particular, when the circumferential surface of the coil 10 is surrounded by the core molded body 30 as in this embodiment, the core molded body 30 covering the circumferential surface of the coil 10 is broken along the second fragile interface portion 37b, making it easy to remove the coil 10 from the core molded body 30. Furthermore, in this embodiment, since the core molded body 30 has multiple second fragile interface portions 37b, when an external force is applied to the core molded body 30, the core molded body 30 that encircles the outer diameter side of the coil 10 is separated into multiple fragments starting from the multiple second fragile interface portions 37b. This makes it easier to remove the coil 10 from the core molded body 30 more efficiently.

[0081] In this embodiment, the porosity of the fragile interface 37 is greater than that of some other parts. More specifically, the fragile interface 37 or a part adjacent to the fragile interface 37 has a higher porosity than the central part 35. As a result, the fragile interface 37 is more brittle than the central part 35 and can be easily broken when an external force is applied to the core molded body 30. In particular, in this embodiment, the porosity of the second fragile interface 37b is greater than that of some other parts. Furthermore, the porosity of the second fragile interface 37b may be greater than that of the first fragile interface 37a. That is, the second fragile interface 37b may be more brittle and easily broken than the first fragile interface 37a. In this case, the porosity of the first fragile interface 37a may be greater than that of the central part 35, or it may be about the same as that of the central part 35. Thus, because the porosity of the second weak interface portion 37b is greater than that of the first weak interface portion 37a, when an external force is applied to the core molded body 30, the second weak interface portion 37b can be destroyed earlier than the first weak interface portion 37a. Since the core molded body 30 is destroyed first at the second weak interface portion 37b, and the core molded body 30 located on the outer diameter side of the coil 10 is divided into multiple parts, it becomes even easier to destroy the core molded body 30 at the first weak interface portion 37a compared to when the core molded body 30 is not divided at the second weak interface portion 37b.

[0082] Furthermore, similar to the first embodiment, in this embodiment, the occupancy rate of recesses on the upper surface (core upper surface 30a) of the core molded body 30 is less than 8.0%.

[0083] Next, the manufacturing method of the coil component 1 in this embodiment (particularly the manufacturing method of the core molded body 30) will be described. The coil component 1 in this embodiment is manufactured by a manufacturing method that includes a coil housing step, a preliminary molding step, a placement step, and a curing step, similar to that described in the first embodiment. The same aspects as in the first embodiment will be omitted from the explanation, and the differences from the first embodiment will be explained in particular.

[0084] As described in the first embodiment, in the coil housing process, the coil 10 is housed in the case 20.

[0085] As shown in Figure 9, in the temporary molding process of this embodiment, a plurality of temporary molded bodies 40 are molded. Specifically, a temporary molded body 40b is positioned on the outer diameter side of the coil 10 and a temporary molded body 40a is positioned above the coil 10. More specifically, in this embodiment, a plurality of temporary molded bodies 40b1, 40b2, 40b3, 40b4 are positioned on the outer diameter side of the coil 10 and a temporary molded body 40a is positioned above the coil 10. In this embodiment, as shown in Figure 9, a total of five temporary molded bodies 40 are molded: four temporary molded bodies 40b are positioned on the outer diameter side of the coil 10 and one temporary molded body 40a is positioned above the coil 10.

[0086] In this embodiment, the temporary molded body 40a, which is positioned above the coil 10, is formed by pressing the kneading material into a mold having a bottomed recess, or by forming it into a predetermined shape (for example, a plate) using a mold and then hollowing out a part of the plate (forming a recess on the lower surface of the plate). In this embodiment, the temporary molded body 40b, which is positioned on the outer diameter side of the coil 10, is formed by pressing the kneading material from above into a mold that penetrates vertically, as described in the first embodiment.

[0087] In the arrangement step of this embodiment, a plurality of temporary molded bodies 40 are arranged in the receiving recess 22 (gap 24). Specifically, first, temporary molded bodies 40b are arranged in the gap 24 on the outer diameter side of the coil 10. In other words, the temporary molded bodies 40b arranged on the outer diameter side of the coil 10 are arranged in the gap 24 defined between the circumferential surface of the coil 10 and the wall portion of the case 20. In this embodiment, each of the plurality of temporary molded bodies 40b is arranged in a part of the gap 24 defined between the circumferential surface of the coil 10 and the wall portion of the case 20, and the gap 24 is filled by the plurality of temporary molded bodies 40b. At this time, the temporary molded bodies 40b may be spaced apart from each other in the circumferential direction of the coil 10, or they may be in contact with each other. The plurality of temporary molded bodies 40b may be arranged in the gap 24 simultaneously, or they may be arranged in the gap 24 one by one in sequence. Next, temporary molded body 40a is arranged in the gap 24 above the coil 10. The temporary molded body 40a, positioned above the coil 10, is placed in a gap 24 defined by the wall portion of the case 20 and the surface of a core 60 separate from the core molded body 30. When the temporary molded body 40a is placed in the gap 24, the lower surface of the temporary molded body 40a positioned above the coil 10 contacts the upper surface of the temporary molded body 40b positioned on the outer diameter side of the coil 10.

[0088] During the curing process, multiple temporary molded bodies 40 are hardened by being pressed and heated from above. When multiple temporary molded bodies 40b are spaced apart in the circumferential direction of the coil 10, when the multiple temporary molded bodies 40 are pressed, the temporary molded bodies 40b deform slightly, and adjacent temporary molded bodies 40b in the circumferential direction of the coil 10 come into close contact with each other. As a result, after the curing process, the multiple temporary molded bodies 40a, 40b become a core molded body 30 having recesses.

[0089] As described above, in this embodiment, the core molded body 30 covers the outer diameter side and the top of the coil 10, and the core molded body 30 has both a first weak interface portion 37a and a second weak interface portion 37b. Alternatively, the core molded body 30 may cover only the outer diameter side of the coil 10. Specifically, the core molded body 30 may be molded into a cylindrical shape that penetrates the coil 10 in the direction of the helical axis, and the coil 10 may be placed inside the cylindrical shape. In this case, the core molded body 30 may have only a weak interface portion 37 (second weak interface portion 37b) along the helical axis of the coil 10.

[0090] <Fourth Embodiment> Figure 12(a) is an explanatory diagram illustrating the manufacturing process of the coil component 1 according to this embodiment, and Figure 12(b) is a perspective view of the core molded body 30 of this embodiment viewed from below. First, an overview of the coil component 1 of this embodiment will be described.

[0091] (Coil component) In the coil component of this embodiment, the porosity, which is the ratio of the volume of voids 32 to the envelope volume of the core molded body 30, is 35% or more.

[0092] Next, the coil component 1 of this embodiment will be described in detail. As shown in Figure 12(b), the coil component 1 of this embodiment differs from the third embodiment in that the core molded body 30 includes a plurality of leg portions 30b that are arranged radially outside the coil 10 and spaced apart from each other in the circumferential direction of the coil 10. In other words, as shown in Figure 12(a), within the case 20, there are hollow portions between adjacent leg portions 30b in the circumferential direction of the coil 10. As shown in Figure 12(b), the plurality of leg portions 30b are members that extend downward from a common part of the core molded body 30. In this embodiment, each of the plurality of leg portions 30b extends from the top plate portion 30c, which will be described later. Alternatively, the leg portions 30b may extend upward from a part located below the coil 10. The core molded body 30 includes two or more leg portions 30b. In this embodiment, the core molded body 30 includes four leg portions 30b. Specifically, the legs 30b are positioned at each of the four corners of the case 20.

[0093] Because the multiple leg portions 30b located radially outside the coil 10 are spaced apart from each other, it becomes easier to remove the core molded body 30 (especially the leg portions 30b) from the circumferential surface of the coil 10 when discarding the coil component 1, compared to the case where the core molded body 30, which is positioned radially outside the coil 10, is integrally formed. Specifically, for example, the leg portions 30b can be removed from the coil 10 by inserting a tool into the gap between the leg portions 30b and using the tool to peel the leg portions 30b away from the circumferential surface of the coil 10. Alternatively, as will be described later, if the core molded body 30 has a first weak interface portion 37a, an external force can be applied to the core molded body 30 to easily remove each leg portion 30b from the coil 10, starting from the first weak interface portion 37a.

[0094] In this embodiment, the side surfaces of the leg portions 30b are in contact with the circumferential surface of the coil 10 and the wall of the case 20, respectively. Alternatively, the side surfaces of the leg portions 30b may be spaced apart from either the circumferential surface of the coil 10 or the wall of the case 20.

[0095] As shown in Figure 12(b), in this embodiment, the core molded body 30 includes a top plate portion 30c. The top plate portion 30c covers the end face 10a of the coil 10 (see Figure 10), which faces the opening side of the housing recess 22 (the upper end face of the coil 10). In this embodiment, the leg portion 30b is integrally formed with the top plate portion 30c. The leg portion 30b extends downward from the top plate portion 30c toward the bottom of the housing recess 22 in the depth direction (vertical direction) of the housing recess 22. Specifically, the leg portion 30b extends downward from each of the four corners of the rectangular top plate portion 30c in this embodiment.

[0096] As shown in Figure 12(b), in this embodiment, a fragile interface portion 37 (particularly a first fragile interface portion 37a) is formed in the core molded body 30. The first fragile interface portion 37a is formed including the interface between the leg portion 30b and the top plate portion 30c. Alternatively, the core molded body 30 may not have a fragile interface portion 37.

[0097] Furthermore, similar to the first embodiment, in this embodiment, the occupancy rate of recesses on the upper surface (core upper surface 30a) of the core molded body 30 is less than 8.0%.

[0098] The coil component 1 of this embodiment is manufactured by a manufacturing method that includes a coil housing step, a pre-forming step, an arrangement step, and a curing step, similar to the first or third embodiment. In the pre-forming step of this embodiment, a plurality of pre-formed bodies 40a and 40b, as shown in Figures 12(a) and 12(b), are formed. In the arrangement step, as shown in Figure 12(a), the pre-formed bodies 40b1 to 40b4 are arranged on the outer circumference of the coil 10. At this time, the plurality of pre-formed bodies 40b1 to 40b4 are arranged spaced apart from each other in the circumferential direction of the coil 10, and there are hollow spaces between the plurality of pre-formed bodies 40b1 to 40b4. After the pre-formed bodies 40b1 to 40b4 are arranged on the outer circumference of the coil 10, the pre-formed body 40a is placed above the coil 10. In the curing step, the plurality of pre-formed bodies 40 are pressed and heated to cure. As a result, the temporary molded bodies 40b1 to 40b4 are fixed to the temporary molded body 40a, forming leg portions 30b, and a fragile interface portion 37 (first fragile interface portion 37a) is formed at the boundary where they are fixed. At this time, even when the multiple temporary molded bodies 40 are pressurized, the multiple temporary molded bodies 40b1 to 40b4 arranged on the outer diameter side of the coil 10 do not come into close contact with each other, and a hollow portion is maintained between the multiple temporary molded bodies 40b1 to 40b4. As a result, the core molded body 30 can have multiple leg portions 30b.

[0099] It should be noted that the present invention is not limited to the embodiments described above, and includes various modifications, improvements, and other forms as long as the objectives of the present invention are achieved. The following modifications can be combined as appropriate.

[0100] The above embodiment encompasses the following technical concept: (1) A method for manufacturing a coil component comprising a coil, a case having a bottomed housing recess for housing the coil, and a core molded body containing magnetic powder and disposed in the housing recess, comprising: a coil housing step of housing the coil in the housing recess; a pre-molding step of forming a pre-molded body having a predetermined shape from a kneaded material of a thermosetting resin and the magnetic powder; a placement step of arranging one or more of the pre-molded bodies in the housing recess of the case; and a curing step of forming the core molded body by pressurizing and heating the pre-molded bodies disposed in the housing recess to cure them, wherein the predetermined shape of the pre-molded body is a shape that follows a gap which is at least a part of the internal space of the housing recess in which the coil is housed in the coil housing step, and the pre-molded body is placed in the gap in the placement step. (2) A coil component comprising a coil, a case having a bottomed housing recess for housing the coil, and a core molded body disposed in the housing recess and containing resin and magnetic powder, wherein the core molded body contains voids, and the void ratio, which is the ratio of the volume of the voids to the envelope volume of the core molded body, is 35.0% or more. (2-1) The coil component according to (2), wherein the width dimension of at least a part of the void 32 is 30.0 μm or more. (3) The coil component according to (2), wherein a plurality of recesses with an opening diameter of 10.0 μm or more are formed on the upper surface of the core molded body, and the occupancy ratio, which is the ratio of the area occupied by the plurality of recesses on the upper surface, is less than 8.0%. (4) The coil component according to (2) or (3), wherein the coil is formed in a spiral shape, and the core molded body is disposed in the space on the inner diameter side of the coil. (5) The coil component according to (4), wherein the core molded body is positioned inward from the end face of the coil in the helical axis direction of the coil, and the end of the core molded body in the helical axis direction includes an inner edge portion which is a part of the inner side in the radial direction of the coil and an outer edge portion which is a part of the outer side in the radial direction of the inner edge portion, and the outer edge portion protrudes in the helical axis direction from the inner edge portion.(6) The coil component according to (5), wherein the void ratio at the outer edge is smaller than the void ratio at the inner edge. (6-1) The coil component according to (5), wherein the void ratio at the outer edge is larger than the void ratio at the inner edge. (7) The coil component according to (4), wherein the core molded body is formed to protrude outward from the annular end face of the coil in the helical axis direction of the coil, a portion of the core molded body that protrudes in the helical axis direction covers the inner surface which is a portion of the radially inner side of the coil at the annular end face, and the outer surface which is a portion of the radially outer side of the annular end face that is larger than the inner surface is exposed from the core molded body. (7-1) The coil component according to (7), wherein the radial dimension of the area covered by the covering portion 31 at the end face 10a is smaller than the radial dimension of the area not covered by the covering portion 31 at the end face 10a. (8) The coil component according to (7), wherein the void ratio of the covering portion that covers the inner surface of the core molded body is smaller than the void ratio of other parts of the core molded body. (8-1) The coil component according to (8), wherein the void ratio of the central portion of the protruding portion is smaller than the void ratio of the main body portion. (8-2) The coil component according to (7), wherein the void ratio of the covering portion that covers the inner surface of the core molded body is larger than the void ratio of other parts of the core molded body. (9) The coil component according to (2) or (3), wherein the core molded body has a fragile interface portion that breaks more easily than other parts of the core molded body when an external force is applied to the core molded body, and the first fragile interface portion extends in a direction intersecting the depth direction of the receiving recess. (9-1) The coil component according to (2) or (3), wherein the core molded body has a fragile interface portion which breaks more easily than other parts of the core molded body when an external force is applied to the core molded body, and the fragile interface portion extends along the depth direction of the receiving recess. (10) The coil component according to (2) or (3), wherein the core molded body has a fragile interface portion which breaks more easily than other parts of the core molded body when an external force is applied to the core molded body, and the second fragile interface portion extends along the depth direction of the receiving recess.(11) The coil component according to (9) or (10), wherein the porosity of the fragile interface portion is greater than that of some other porosities. (11-1) The coil component according to (11), wherein the porosity of the second fragile interface portion is greater than that of some other porosities. (11-2) The coil component according to (11) or (11-1), wherein the porosity of the second fragile interface portion is greater than that of the first fragile interface portion. (12) The coil component according to (2) or (3), wherein the core molded body includes a plurality of leg portions arranged radially outward from the coil and spaced apart from each other in the circumferential direction of the coil. (13) The coil component according to (12), wherein the core molded body includes a top plate portion that covers the end face of the coil facing the opening side of the housing recess, the leg portions being integrally formed with the top plate portion and extending from the top plate portion toward the bottom of the housing recess in the depth direction of the housing recess.

[0101] 1 Coil component 10 Coil 10a End face 10a1 Inner surface 10a2 Outer surface 12 Coil body 12a Lead-out part 14 Bobbin 20 Case 22 Retaining recess 24 Gap 26 Notch 30 Core molded body 30a Core top surface 30b Leg part 30c Top plate part 31 Covering part 32 Gap 32a Filling part 33 Main body part 34 Recess 35 Center part 36 End part 36a Inner edge part 36b Outer edge part 37 Weak interface part 37a First weak interface part 37b Second weak interface part 38 Protruding parts 40, 40a, 40b, 40b1, 40b2, 40b3, 40b4 Temporary molded body 50 Terminal 60 Core 62 Second core 64 Third core

Claims

1. A method for manufacturing a coil component comprising a coil, a case having a bottomed receiving recess for housing the coil, and a core molded body containing magnetic powder and disposed in the receiving recess, comprising: a coil housing step of housing the coil in the receiving recess; a pre-molding step of forming a pre-molded body having a predetermined shape from a kneaded material comprising a thermosetting resin and the magnetic powder; a placement step of arranging one or more of the pre-molded bodies in the receiving recess of the case; and a curing step of forming the core molded body by pressurizing and heating the pre-molded bodies disposed in the receiving recess to cure them, wherein the predetermined shape of the pre-molded body is a shape that follows a gap which is at least a part of the internal space of the receiving recess in which the coil is housed in the coil housing step, and the pre-molded body is placed in the gap in the placement step.

2. A coil component comprising a coil, a case having a bottomed housing recess for housing the coil, and a core molded body disposed in the housing recess and containing resin and magnetic powder, wherein the core molded body contains voids, and the porosity, which is the ratio of the volume of the voids to the envelope volume of the core molded body, is 35.0% or more.

3. The coil component according to claim 2, wherein a plurality of recesses having an opening diameter of 10.0 μm or more are formed on the upper surface of the core molded body, and the occupancy rate, which is the ratio of the area occupied by the plurality of recesses on the upper surface, is less than 8.0%.

4. The coil component according to claim 2 or 3, wherein the coil is formed in a spiral shape, and the core molded body is disposed in the space on the inner diameter side of the coil.

5. The coil component according to claim 4, wherein the core molded body is positioned inward from the end face of the coil in the helical axis direction of the coil, and the end of the core molded body in the helical axis direction includes an inner edge portion which is a part of the inner side in the radial direction of the coil and an outer edge portion which is a part of the outer side in the radial direction of the inner edge portion, and the outer edge portion protrudes in the helical axis direction from the inner edge portion.

6. The coil component according to claim 5, wherein the void ratio at the outer edge is smaller than the void ratio at the inner edge.

7. The coil component according to claim 4, wherein the core molded body is formed to protrude outward from the annular end face of the coil in the helical axis direction of the coil, a portion of the core molded body that protrudes in the helical axis direction covers the inner surface which is a portion of the radially inner side of the coil at the annular end face, and the outer surface which is a portion of the radially outer side of the annular end face that is exposed from the core molded body.

8. The coil component according to claim 7, wherein the void ratio of the covering portion, which is a part that covers the inner surface of the core molded body, is smaller than the void ratio of other parts of the core molded body.

9. The coil component according to claim 2 or 3, wherein the core molded body has a fragile interface portion which breaks more easily than other parts of the core molded body when an external force is applied to the core molded body, and the first fragile interface portion extends in a direction intersecting the depth direction of the receiving recess.

10. The coil component according to claim 2 or 3, wherein the core molded body has a fragile interface portion which breaks more easily than other parts of the core molded body when an external force is applied to the core molded body, and the second fragile interface portion extends along the depth direction of the receiving recess.

11. The coil component according to claim 9 or 10, wherein the porosity of the fragile interface portion is greater than the porosity of some other portions.

12. The coil component according to claim 2 or 3, wherein the core molded body includes a plurality of legs that are positioned radially outward of the coil and spaced apart from each other in the circumferential direction of the coil.

13. The coil component according to claim 12, wherein the core molded body includes a top plate portion that covers the end face of the coil that faces the opening side of the housing recess, and the leg portion is integrally formed with the top plate portion and extends from the top plate portion toward the bottom of the housing recess in the depth direction of the housing recess.

Images