Coil component and manufacturing method thereof

Abstract

To provide a coil component capable of preventing an external electrode from being damaged even when an impact is applied.SOLUTION: A coil component includes a substrate having metal magnetic particles and a binder, a coil conductor disposed within the substrate, and an external electrode provided on the surface of the substrate and electrically connected to the coil conductor. In a cross section passing through a joint between the substrate and the external electrode, the length of the electrode-forming surface of the substrate facing the external electrode is 150% or more of the horizontally projected length of the electrode-forming surface.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a coil component and a method for manufacturing a coil component. [Background technology]

[0002] Coil components are mounted in various electronic devices, such as portable electronic devices, and are therefore required to be smaller and have higher performance. Conventionally, coil components mounted in electronic devices have a coil conductor and a base body surrounding the coil conductor, and the base body is a metal composite base body. For example, Patent Document 1 discloses a coil component including a coil and a magnetic core material, at least a portion of which is made of a thermoset body of a metal magnetic composite material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-202325 Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, the applications of coil components are expanding, for example, they are being mounted in portable electronic devices, etc. As the applications of coil components expand, there is a growing demand for coil components to have impact resistance so that the electronic devices, etc. mounted therein will not be damaged if they are dropped, for example.

[0005] When a coil component has a coil conductor and a base disposed so as to surround the coil conductor, external electrodes electrically connected to the coil conductor are formed on the surface of the base using a metal paste or the like in order to mount the coil component on an electronic device and connect it to a circuit. However, when an electronic device equipped with a coil component is dropped, the external electrodes may peel off from the base, resulting in damage.

[0006] An object of the present disclosure is to provide a coil component that can prevent external electrodes from being damaged even when an impact is applied. [Means for solving the problem]

[0007] The coil component of the present disclosure includes a substrate containing metal magnetic particles and a binder; a coil conductor disposed in the substrate; an external electrode provided on a surface of the base and electrically connected to the coil conductor; In a cross section passing through the joint between the base and the external electrode, the length of the electrode formation surface of the base facing the external electrode is 150% or more of the horizontal projection length of the electrode formation surface. [Effects of the Invention]

[0008] According to the present disclosure, it is possible to provide a coil component that can prevent external electrodes from being damaged even when an impact is applied. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view of a coil component according to one embodiment of the present disclosure. [Figure 2] FIG. 2 is a cross-sectional view taken along line AA in FIG. [Figure 3] FIG. 3 is an enlarged schematic view of region B in FIG. [Figure 4] FIG. 4 is an explanatory diagram of the length of the electrode formation surface and the horizontal projection length of the electrode formation surface. [Figure 5] FIG. 5 is a diagram illustrating the correlation between the ratio (LB / LA) of the length LB of the electrode-forming surface to the horizontal projection length LA of the electrode-forming surface, and the impact strength in a drop test. [Figure 6] FIG. 6 is a flow diagram of a method for manufacturing a coil component according to one embodiment of the present disclosure. [Figure 7] FIG. 7 is an explanatory diagram of a method for manufacturing a coil component according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present disclosure (hereinafter referred to as "embodiment") will be described in detail below, but the present disclosure is not limited thereto. In this specification and drawings, components having substantially the same functional configuration may be designated by the same reference numerals to avoid redundant description. The drawings are schematic diagrams shown to explain the arrangement of each component, and are not necessarily drawn to scale.

[0011] In this specification, the names of components, parts, etc., such as the first base and the second base, may be described with "first" or "second," but "first," "second," etc. are merely used to distinguish between the components and to prevent confusion during description. Therefore, "first," "second," etc., do not represent placement, priority, etc. Furthermore, when there is no particular risk of confusion or when referring to components collectively, they may be simply written as "base," etc. [Coil parts] The coil component of this embodiment will be described below.

[0012] FIG. 1 is a perspective view of a coil device 10 according to this embodiment. To clarify the structure, the coil conductor 12, which is covered by a base 11 and therefore not visible from the outside, and components connected to the coil conductor 12 are also shown. FIG. 2 is a cross-sectional view of the coil device taken along line AA in FIG. 1, i.e., a plane passing through the central axis CA. FIG. 3 is an enlarged schematic view of region B in FIG. 2. FIG. 4 is an explanatory diagram of the length of the electrode-forming surface and the horizontally projected length of the electrode-forming surface. FIG. 5 is an explanatory diagram of the correlation between the ratio (LB / LA) of the length LB of the electrode-forming surface to the horizontally projected length LA of the electrode-forming surface and impact strength in a drop test. Although the cross section taken along line AA in FIG. 1 does not include the lead-out portion 122, the lead-out portion 122 is also shown in FIG. 2 by a two-dot chain line to clarify its relationship with the coil conductor 12 and other components. (1) Coil component configuration A coil component 10 of this embodiment will be described with reference to Figures 1 to 5. The coil component of this embodiment is an inductor, and can be used as a power inductor incorporated in a power line or as various other inductors.

[0013] As shown in FIG. 1, the coil device 10 includes a base 11, a coil conductor 12 disposed in the base 11, and an external electrode 13 provided on the surface of the base 11 and electrically connected to the coil conductor 12.

[0014] The coil component 10 can be mounted on a mounting substrate 21 provided with land portions 22. The coil component 10 is mounted on the mounting substrate 21 by joining the external electrodes 13 to the land portions 22. The circuit board 20 can include the coil component 10 and the mounting substrate 21 on which the coil component 10 is mounted. In addition to the coil component 10, the circuit board 20 can also include various electronic components necessary to form an electronic circuit.

[0015] The circuit board 20 equipped with the coil component 10 and the like can be mounted in a variety of electronic devices, such as various mobile terminals such as smartphones, electrical components for automobiles, servers and personal computers used in offices and data centers, control devices for various factories, etc. The electronic devices on which the coil component 10 of the present embodiment is mounted are not limited to those explicitly mentioned in this specification.

[0016] The shape of the base 11 is not particularly limited, but may have, for example, a rectangular parallelepiped shape as shown in FIG. 1. The rectangular parallelepiped shape referred to here does not have a strict geometrical meaning; for example, the corners connecting the respective faces may be chamfered, or the corners of the faces may not be right angles. In FIG. 1, each face of the base 11, such as the first main face 11a, is illustrated as a flat face, but may also be a curved face. Furthermore, each side connecting the respective faces of the base 11, i.e., the boundary line of each face, may not be a straight line, but may be a curve, etc., in accordance with the shape of each face.

[0017] The base 11 can have, for example, a first main surface 11a, a second main surface 11b, a first end surface 11c, a second end surface 11d, a first side surface 11e, and a second side surface 11f. The first main surface 11a and the second main surface 11b are surfaces located on opposite sides of the base 11. The first end surface 11c and the second end surface 11d are surfaces located on opposite sides of the base 11. The first side surface 11e and the second side surface 11f are surfaces located on opposite sides of the base 11. The outer edge of the first main surface 11a can be defined by four sides. In the case of FIG. 1, the outer edge of the first main surface 11a can be defined by a pair of short sides and a pair of long sides. Similar to the first main surface 11a, the outer edge of the second main surface 11b can also be defined by a pair of short sides and a pair of long sides. The first end face 11c and the second end face 11d can connect the short sides of the first main surface 11a and the short sides of the second main surface 11b. The first side face 11e and the second side face 11f can connect the long sides of the first main surface 11a and the long sides of the second main surface 11b.

[0018] When the coil component 10 is mounted on a mounting substrate 21 as shown in FIG. 1, the first main surface 11a is located on the upper side of the base 11, and the second main surface 11b is located on the lower side of the base 11. For this reason, the first main surface 11a is sometimes referred to as the "upper surface," and the second main surface 11b is sometimes referred to as the "lower surface." Because the coil component 10 is disposed so that the second main surface 11b faces the mounting substrate 21, the second main surface 11b is sometimes referred to as the "mounting surface." In this specification, unless otherwise understood in the context, the "length" direction, "width" direction, and "height" direction of the coil component 10 are defined as the "L-axis" direction, "W-axis" direction, and "T-axis" direction in FIG. 1, respectively. The L-axis, W-axis, and T-axis are perpendicular to each other.

[0019] The size of the coil component 10 is not particularly limited, but the coil component 10 may be a small coil component. In this case, the coil component 10 may have, for example, a length dimension (dimension in the L-axis direction) of 0.2 mm or more and 4.0 mm or less, a width dimension (dimension in the W-axis direction) of 0.1 mm or more and 4.0 mm or less, and a height dimension (dimension in the T-axis direction) of 0.1 mm or more and 4.0 mm or less. The coil component 10 may be configured so that the length dimension is greater than the width dimension.

[0020] When the length dimension of the coil component 10 is greater than the width dimension, the direction along the L axis can be referred to as the long-side direction of the coil component 10, and the direction along the W axis can be referred to as the short-side direction of the coil component 10. The dimension of the coil component 10 in the short-side direction may be 3.0 mm or less. At least one of the length dimension, width dimension, and height dimension of the coil component 10 may be 4.0 mm or less, 2.0 mm or less, 1.0 mm or less, or 0.65 mm or less. The coil component 10 may be thin. Specifically, the length dimension of the coil component 10 may be greater than the height dimension. The length dimension of the coil component 10 may be at least two times, or at least three times, the height dimension.

[0021] The height dimension of the coil component 10 may be 1 mm or less.

[0022] These dimensions are merely examples, and the coil device 10 of this embodiment can have any dimensions. (2) Coil conductor The coil conductor 12 has a winding portion 121 extending in the circumferential direction around the central axis CA of the coil conductor 12, and a lead portion 122. The lead portion 122 has a first lead portion 122A extending from a first end portion, which is an end portion along the longitudinal direction of the winding portion 121, to a second main surface 11b, which is the lower surface of the base 11. The lead portion 122 also has a second lead portion 122B extending from a second end portion, which is located opposite the first end portion of the winding portion 121, to the second main surface 11b, which is the lower surface of the base 11. The coil conductor 12 is disposed in the base 11, i.e., inside the base 11. In other words, the coil conductor 12 is located inside the first main surface 11a, the second main surface 11b, the first end surface 11c, the second end surface 11d, the first side surface 11e, and the second side surface 11f of the base 11, and is embedded in the base 11. An end face of the first lead portion 122A and an end face of the second lead portion 122B are exposed to the outside of the base 11 from the second main surface 11b, which is the lower surface of the base 11. The first lead portion 122A and the second lead portion 122B can be connected to the external electrode 13 at their end faces exposed from the base 11.

[0023] The central axis CA of the coil conductor 12 may be a straight line that passes through the geometric center of gravity of the coil conductor 12 when viewed from the first main surface 11a, which is the top surface, and the geometric center of gravity of the coil conductor 12 when viewed from the second main surface 11b, which is the bottom surface, along the T-axis. The central axis CA may be, for example, an axis along the T-axis.

[0024] 1, the winding portion 121 includes a first winding portion 123 wound around a central axis CA from a first lead-out portion 122A for a plurality of turns, and a second winding portion 124 located closer to the first main surface 11a, which is the upper surface of the base 11, than the first winding portion 123. In other words, in FIG. 1, the winding portion 121 has a two-layer structure in which the first winding portion 123 and the second winding portion 124 are stacked along the T-axis. An end of the first winding portion 123 is connected to the first lead-out portion 122A. An end of the second winding portion 124 is connected to the second lead-out portion 122B.

[0025] As shown in FIG. 1 , the first winding portion 123 and the second winding portion 124 can each have one or more turns in the circumferential direction around the central axis CA. The number of turns in the first winding portion 123 and the second winding portion 124 is not particularly limited, and can be, for example, 1.5 turns or 2.5 turns, respectively. Note that the number of turns in the first winding portion 123 and the second winding portion 124 is not limited to the number of turns explicitly described in this specification. The winding portion 121 may have a single-layer structure or a three- or more-layer structure.

[0026] The coil conductor 12 can be made of a material with excellent conductivity, such as copper (Cu), silver (Ag), or gold (Au), and can be formed, for example, in a strip shape. The surface of the coil conductor 12 may be covered with an insulating coating. The insulating coating that covers the coil conductor 12 is not particularly limited, but can be made of, for example, a thermosetting resin with excellent insulation properties. Specifically, this insulating coating can contain one or more resins with excellent insulation properties selected from polyurethane, polyamideimide, polyimide, polyester, polyester-imide, etc. (3) About the base Next, the configuration of the base 11 will be described.

[0027] The substrate 11 can be a metal composite substrate made of a composite magnetic material. The metal composite substrate 11 can be obtained, for example, by pressure molding a slurry, granules, or pellets obtained by kneading a composite magnetic material containing metal magnetic particles and a binding material (binder).

[0028] For this reason, for example, as shown in Fig. 3, which is an enlarged schematic view of region B including a part of base 11 in Fig. 2, base 11 can contain metal magnetic particles 31 and a binder. The binder can contain resin 32 as a component that connects metal magnetic particles 31. (3-1) Materials contained in the substrate (Metal magnetic particles) The metal magnetic particles contained in the base 11 may be composed of one type of metal magnetic particles or may be a mixture of multiple types of metal magnetic particles. In the base 11, the multiple metal magnetic particles are bound together by a resin contained in the binder.

[0029] The metal magnetic particles contained in the base 11 can be one or more types selected from, for example, (1) metal particles such as iron (Fe) and nickel (Ni), (2) crystalline alloy particles such as Fe-Si-Cr alloy, Fe-Si-Al alloy, and Fe-Ni alloy, and (3) amorphous alloy particles such as Fe-Si-Cr-BC alloy and Fe-Si-Cr-B alloy. The metal magnetic particles contained in the base 11 may also be mixed particles of one or more types selected from the above (1) to (3).

[0030] The composition of the metal magnetic particles contained in base 11 is not limited to the above. For example, the metal magnetic particles contained in base 11 may be one or more types selected from a Co-Nb-Zr alloy, an Fe-Zr-Cu-B alloy, an Fe-Si-B alloy, an Fe-Co-Zr-Cu-B alloy, an Ni-Si-B alloy, and an Fe-Al-Cr alloy. The metal magnetic particles contained in base 11 may also contain P.

[0031] The Fe-based metal magnetic particles contained in the substrate 11 may contain 95 wt% or more of Fe. An insulating film may be disposed on the surface of the metal magnetic particles. The insulating film may be an oxide film formed by oxidizing the metal element contained in the metal magnetic particles. The insulating film provided on the surface of each metal magnetic particle may be a silicon oxide film. The silicon oxide film can be coated on the surface of the metal magnetic particles by, for example, a sol-gel method.

[0032] The average particle size of the metal magnetic particles is not particularly limited, but may be, for example, 1 μm or more and 60 μm or less, or 1 μm or more and 10 μm or less.

[0033] The average particle size of the metal magnetic particles contained in the base 11 and the inorganic particles described below can be measured and calculated, for example, by the following procedure. First, a cross section of the base 11 along the height direction (T-axis direction) is exposed, and the volume-based particle size distribution is determined based on an SEM image of the exposed cross section taken with a scanning electron microscope (SEM). The particle size of each particle can be determined as a circular equivalent diameter calculated from the cross-sectional area of ​​the particle in the taken SEM image. Then, the volume of each particle when it is treated as a sphere is calculated from the calculated particle size, and the volume-based particle size distribution is determined. The average particle size is then determined based on the calculated volume-based particle size distribution. For example, the average particle size (median diameter (D50)) calculated from the volume-based particle size distribution of the metal magnetic particles determined based on the SEM image can be used as the average particle size of the metal magnetic particles. The particle size distribution of each particle contained in the base 11 may be measured by a laser diffraction scattering method in accordance with JIS Z 8825 (2022). The particle size distribution of each particle contained in the base 11 can be measured using a laser diffraction / scattering device. For example, a laser diffraction / scattering particle size distribution measuring device (model number: LA-960) manufactured by Horiba, Ltd., Kyoto City, Kyoto Prefecture, Japan, can be used to measure the particle size distribution of each particle contained in the base 11.

[0034] The content ratio of the metal magnetic particles in the base 11 can be selected depending on the properties required for the base 11 and the coil component 10, and is not particularly limited. The content ratio of the metal magnetic particles in the base 11 may be, for example, 85 vol% or more, or may be 87 vol% or more. The upper limit of the content ratio of the metal magnetic particles in the base 11 is not particularly limited, but may be, for example, less than 100 vol%. When the base 11 contains multiple types of metal magnetic particles, the content of the metal magnetic particles refers to the total content of the multiple types of metal magnetic particles. The content ratio of the metal magnetic particles in the base 11 can be determined as the abundance ratio based on an SEM image of an exposed cross section taken with a scanning electron microscope (SEM). The area ratio of the metal magnetic particles to the cross section of the base 11, which corresponds to the abundance ratio of the metal magnetic particles determined from the cross section, may be, for example, 85% or more, or even 87% or more. The upper limit of the area ratio of the metal magnetic particles to the cross section of the base 11, which corresponds to the abundance ratio of the metal magnetic particles, is not particularly limited, but may be, for example, less than 100%. (Binding material) The substrate 11 may contain a binder.

[0035] The binder may include, for example, a thermosetting resin having excellent insulating properties. Examples of resin materials for the binder include one or more selected from epoxy resin, polyimide resin, polystyrene (PS) resin, high-density polyethylene (HDPE) resin, polyoxymethylene (POM) resin, polycarbonate (PC) resin, polyvinylidene fluoride (PVDF) resin, phenolic resin, polytetrafluoroethylene (PTFE) resin, and polybenzoxazole (PBO) resin. (Inorganic particles) The base 11 may contain inorganic particles. When the base 11 contains inorganic particles, the inorganic particles may be one or more types selected from SiO2 particles (silica particles), Al2O3 particles (alumina particles), glass-based particles, etc., and may be, for example, a mixture of one or more types selected from the above-mentioned SiO2 particles, etc.

[0036] The inorganic particles can have an average particle size of, for example, 0.01 μm or more and 1 μm or less.

[0037] When base 11 contains inorganic particles, the inorganic particles can fill the gaps between the metal magnetic particles and stabilize the arrangement of the metal magnetic particles. Therefore, by including inorganic particles in base 11, the mechanical strength of base 11 can be improved. (3-2) Structure of the substrate Next, an example of the structure of the base 11 will be described with reference to FIG.

[0038] The substrate 11 can have a first substrate 111 and a second substrate 112 .

[0039] Since the base 11 has the first base 111 and the second base 112, the position of the coil conductor 12 can be precisely adjusted in the process of manufacturing the coil component 10, and the coil conductor 12 can be appropriately positioned within the base 11. This allows the characteristics of the coil component 10 to be accurately controlled, and high performance can be achieved.

[0040] The first substrate 111 may have a plate-like shape as shown in FIG. 2, and has a first surface 111A that faces the coil conductor 12, and a second surface 111B that is the surface opposite to the first surface 111A.

[0041] The first surface 111A is a surface on which the coil conductor 12 is placed, and therefore can be made flat.

[0042] The second surface 111B is the same plane as the first main surface 11a of the base 11. Therefore, the second surface 111B may also be a flat surface. However, the second surface 111B is not limited to this form and may have any shape. (4) External electrodes The external electrode 13 is electrically connected to the coil conductor 12 via the first lead portion 122A and the second lead portion 122B. Therefore, the external electrode 13 can be provided, for example, on the second main surface 11b, which is the lower surface of the base 11. In FIGS. 1 and 2, one external electrode 13 is configured and arranged to contact not only the second main surface 11b, which is the lower surface of the base 11, but also the first end surface 11c, the first side surface 11e, and the second side surface 11f. In FIGS. 1 and 2, the other external electrode 13 is configured and arranged to contact not only the second main surface 11b, which is the lower surface of the base 11, but also the second end surface 11d, the first side surface 11e, and the second side surface 11f. However, this is not limited to this configuration. For example, the external electrode 13 may be configured and arranged to contact only the second main surface 11b, which is the lower surface of the base 11, and not to contact any surfaces of the base 11 other than the second main surface 11b. The external electrode 13 can be arranged so as to cover at least a part of the second main surface 11b, which is the lower surface of the base 11. In one embodiment, the external electrode 13 may be configured and arranged so as not to contact the first main surface 11a, which is the upper surface of the base 11. This allows the height dimension of the coil device 10 to be particularly small.

[0043] The external electrode 13 may include a metal layer (metal foil) formed by applying a conductive paste to the surface of the base 11 by screen printing or the like and then heating the applied conductive paste. The thickness of the metal layer is not particularly limited and may be, for example, 1 μm or more and 5 μm or less. The conductive paste may include one or more highly conductive materials selected from the group consisting of silver (Ag), palladium (Pd), copper (Cu), aluminum (Al), nickel (Ni), and alloys containing one or more elements selected from these elements. The metal content of the metal layer may be, for example, 99 wt% or more. The external electrode 13 may include a plating layer formed on the metal layer. The plating layer may include two or more layers. When the plating layer includes two or more layers, the configuration of the two or more plating layers is not particularly limited and may include, for example, a Ni plating layer and a Sn plating layer disposed on the outer side of the Ni plating layer. The thickness of the plating layer may be, for example, 1 μm or more and 5 μm or less. When the external electrodes 13 include a metal layer and a plating layer, the thickness of the external electrodes 13 may be, for example, not less than 5 μm and not more than 10 μm.

[0044] The external electrode 13 may have a conductive resin layer between the metal layer and the plating layer. When the external electrode 13 includes a metal layer, a plating layer, and a conductive resin layer, the thickness of the external electrode 13 may be, for example, 10 μm or more and 20 μm or less.

[0045] Therefore, the external electrode 13 may have a structure in which a metal layer 131 and a conductive resin layer 132 are laminated, as shown in FIG. 3, which is an enlarged view of region B in FIG.

[0046] By forming the external electrode 13 into a structure in which the metal layer 131 and the conductive resin layer 132 are laminated, the conductive resin layer 132 can absorb the force applied to the external electrode 13, thereby preventing damage to the external electrode 13. In addition, the adhesion of the external electrode 13 to the base 11 can be improved.

[0047] Furthermore, the external electrode 13 may further include a plating layer, and may have a structure in which the metal layer 131, the conductive resin layer 132, and the plating layer 133 are laminated.

[0048] The configuration of the external electrode 13 may vary depending on the location where the external electrode 13 is provided, such as the surface of the base 11 where it is provided. For example, when the coil component 10 is mounted on the mounting board 21, the external electrode 13 can have a conductive resin layer 132 on the second main surface 11b, which is the lower surface of the base 11 and serves as the mounting surface, in order to absorb the force applied to the coil component 10.

[0049] Furthermore, when the external electrode 13 is provided on a surface other than the second main surface 11b of the base 11, for example, on one or more surfaces selected from the first end surface 11c, the second end surface 11d, the first side surface 11e, and the second side surface 11f, the external electrode 13 on the first end surface 11c, etc. may have a plating layer 133. By having the plating layer 133 on the external electrode 13 provided on the first end surface 11c, etc., the adhesion of the external electrode 13 to the base 11 can be particularly improved.

[0050] The external electrodes 13 may have the same configuration regardless of the surface of the base 11 on which they are placed. (5) Surface characteristics of the substrate The inventors of the present invention have conducted research into a coil component that can prevent external electrodes 13 from being damaged, such as by peeling off from base 11, even when an impact is applied.

[0051] As a result, it was discovered that by providing predetermined surface characteristics on the surface of the base 11 facing the external electrode 13, damage to the external electrode 13 due to peeling off from the base 11, etc., can be prevented when an impact is applied to the coil component 10, and the present invention was completed. (5-1) Surface characteristics of the electrode formation surface of the substrate Fig. 3 shows an enlarged schematic view of region B surrounded by a dotted line in Fig. 2. Fig. 3 is a partially enlarged view of a cross section passing through joint 30 between base 11 and external electrode 13. Fig. 3 is also a cross section taken along the lamination direction of base 11 and external electrode 13.

[0052] As shown in FIG. 3, the substrate 11 can contain metal magnetic particles 31 and a resin 32 contained in a binder.

[0053] The external electrode 13 can include, for example, a metal layer 131 , a conductive resin layer 132 , and a plating layer 133 .

[0054] As already explained, the base 11 may contain inorganic particles, etc., and the external electrode 13 may be configured without the conductive resin layer 132 or the plating layer 133, so each layer is not limited to the form shown in Figure 3.

[0055] According to the investigations of the inventors of the present invention, in a cross section passing through the joint 30 between the base 11 and the external electrode 13 as shown in Figure 3, the length of the electrode formation surface 33 of the base 11 facing the external electrode 13 can be made to be 150% or more of the horizontal projection length of the electrode formation surface 33.

[0056] The length of the electrode formation surface 33 and the horizontal projection length of the electrode formation surface 33 will be described using Figure 4. Like Figure 3, Figure 4 is a diagram further schematically illustrating a cross section passing through the joint 30 between the base 11 and the external electrode 13 and along the lamination direction of the base 11 and the external electrode 13. Figure 4 shows only the members necessary for the explanation in a simplified manner.

[0057] As shown in FIG. 4, the substrate 11 has an electrode forming surface 33 facing the external electrode 13, which has minute recesses and projections, and the external electrode 13 can be filled into these recesses as well.

[0058] The length LB of the electrode-forming surface 33 of the base 11 is the length measured along the surface of the electrode-forming surface 33 of the base 11. In the case of Fig. 4, the length LB of the electrode-forming surface is calculated by adding together the surface lengths LB1 to LB9 of each portion of the electrode-forming surface 33, and more specifically, the length LB is calculated by LB = LB1 + LB2 + LB3 + LB4 + LB5 + LB6 + LB7 + LB8 + LB9.

[0059] The horizontal projection length of the electrode formation surface 33 of the base 11 is the length when the electrode formation surface 33 is projected onto a horizontal plane, and corresponds to LA in the case of FIG.

[0060] Therefore, the ratio R (%) (hereinafter also simply referred to as "ratio") of the length LB of the electrode forming surface 33 facing the external electrode 13 of the base 11 to the horizontal projection length LA of the electrode forming surface 33 is calculated by the following formula (1):

[0061] R = LB ÷ LA × 100 (1) More specifically, the horizontal projection length LA of the electrode formation surface and the length LB of the electrode formation surface can be determined, for example, by the following procedure.

[0062] As explained using Figures 2, 3, and 4, a sample for evaluating the bonding surface is prepared, which passes through the bonding portion 30 between the base 11 and the external electrode 13 and exposes a cross section along the lamination direction of the base 11 and the external electrode 13.

[0063] The sample for evaluation of the bonded surface is observed using a scanning electron microscope (SEM) or the like. At this time, the position and direction of the observation field are selected so that it includes the bonded portion 30 and crosses the electrode formation surface 33 of the base 11. An observation image magnified 2000 times is obtained for the selected observation field. In the following explanation, the stacking direction of the base 11 and the external electrode 13 is referred to as the height direction.

[0064] Then, in the obtained observation image, a straight line is drawn between the two highest points along the height direction on the contour line of the electrode formation surface 33, and this straight line is used as the reference line, i.e., the horizontal plane, for determining the horizontal projection length LA.

[0065] Next, a region of 50 μm in length along the straight line is selected and set as the horizontal projection length LA, and the length of the contour line of electrode-forming surface 33 located within the selected region, i.e., the length LB of electrode-forming surface 33, is determined. Note that the length of the contour line of electrode-forming surface 33 is the length of the contour line connecting the surfaces of metal magnetic particles 31 and resin 32 that make up base 11 that face external electrode 13, as explained using FIG. 4.

[0066] Then, by substituting the calculated horizontal projection length LA of the electrode formation surface and the length LB of the electrode formation surface into equation (1), the ratio R described above can be calculated.

[0067] By setting the ratio R to 150% or more, it is possible to ensure a sufficient contact area between the base 11 and the external electrode 13, thereby improving the adhesion between the base 11 and the external electrode 13. Furthermore, by setting the ratio R to 150% or more, it is possible to make the surface of the base 11 uneven rather than smooth. This allows the base 11 to include portions that are not directly affected by an impact when the coil device 10 is subjected to the impact, making it difficult for the external electrode 13 to peel off.

[0068] Furthermore, in the coil component 10 of this embodiment, external electrodes 13 can be provided on multiple surfaces of the base 11, as shown in, for example, FIGS. 1 and 2 . In the coil component 10 of this embodiment, providing electrode-forming surfaces on multiple surfaces of the base 11 prevents the external electrodes 13 from being damaged when an impact is applied to the coil component 10. For example, in the coil component 10 shown in FIG. 2 , electrode-forming surfaces 33 are provided on surfaces opposite to each other on the base 11, such as the first end surface 11 c and the second end surface 11 d, and external electrodes 13 are provided on each electrode-forming surface 33, thereby enabling the coil component 10 to withstand impacts from multiple directions. In addition, in the coil component 10, electrode-forming surfaces 33 are provided on adjacent surfaces, such as the second main surface 11 b and the first end surface 11 c, and external electrodes 13 are provided on each electrode-forming surface 33, thereby enabling the coil component 10 to withstand impacts from multiple directions.

[0069] 5 and Table 1 show a correlation diagram and specific numerical values ​​between the ratio R of the electrode formation surface 33 of the first end face 11c and the second end face 11d of the base 11 and the impact strength when damage to the coil component is confirmed in an impact test in which the coil component is dropped after being mounted on a mounting board. Damage to the coil component means that the external electrodes have been visually peeled off from the base.

[0070] The coil components used in the test had the structure shown in Figures 1 and 2, and were manufactured under the same conditions except that they were configured to have different ratios R on the electrode formation surface 33 of the base 11. Multiple coil components with the same ratio R were manufactured, and the impact strength applied during the drop test was changed, and the impact strength when the external electrode peeled off from the base was recorded and used as the impact strength for each ratio R.

[0071] The impact test is performed by soldering a coil component to a board and dropping the board. In this case, the coil component is approximately cubic, measuring 4.0 mm in length, and the external electrodes contain a conductive resin layer. The board with the soldered coil component is fixed to the impact tester so that the direction of the drop is the direction of the coil component as seen from the board, and the maximum acceleration at which the coil component breaks after the test is determined. The presence or absence of breakage is determined for 30 samples under each condition, and if even one breaks, it is considered to have broken, i.e., is damaged.

[0072] As a result, as shown in Figure 5, it was confirmed that the impact strength increases sharply when the ratio R, LB / LA, is about 150%, that is, the external electrodes 13 are less likely to break when an impact is applied to the coil component. It was also confirmed that the impact strength becomes sufficiently high when the ratio R is about 200%, and no significant change is observed.

[0073] [Table 1] In a cross section passing through the joint 30, the length LB of the electrode formation surface 33 of the base 11 may be 200% or more of the horizontal projection length LA of the electrode formation surface 33. By making the ratio R 200% or more, the adhesion between the base 11 and the external electrode 13 is further improved, and even if an impact is applied to the coil device 10, damage to the external electrode 13 can be particularly prevented.

[0074] 1 and 2, when external electrodes 13 are provided on multiple surfaces of base 11, the ratio R may be different depending on the surface on which external electrodes 13 are provided. For example, the ratio R may be larger on first end surface 11c, second end surface 11d, first side surface 11e, and second side surface 11f of base 11 than on second main surface 11b, and may be, for example, 200% or more. Furthermore, the ratio R may be the same regardless of the surface on which external electrodes 13 are provided.

[0075] It is believed that the more irregularities there are on the electrode-forming surface 33 of the base 11 and the greater the degree of waviness, the more adhesiveness can be improved between the base 11 and the external electrode 13. However, if the degree (amplitude) of the waviness of the irregularities on the electrode-forming surface 33 of the base 11 becomes excessively large, it becomes necessary to increase the thickness of the external electrode 13 in order to fill in the irregular portions, which may result in an increase in the size of the coil component 10, etc.

[0076] Therefore, it is preferable that the ten-point mean roughness Rz of the electrode formation surface 33 is smaller than the maximum thickness Tmax of the external electrode 13. By making the ten-point mean roughness Rz of the electrode formation surface 33 smaller than the maximum thickness Tmax of the external electrode 13, the thickness of the external electrode 13 can be made thinner, and the coil component 10 can be made smaller.

[0077] The ten-point average roughness Rz can be measured in accordance with JIS B 0601 (2013). Specifically, for example, it can be measured using a laser microscope (Keyence, Model: VK-X3000) with an observation field size of 200 μm × 280 μm and a magnification of 50 times.

[0078] In the measurement, the undulation curve of the electrode formation surface 33 is used as a reference, and the parts higher than the undulation curve are defined as convex parts, and the parts lower than the undulation curve are defined as concave parts, and the height (depth) of each is determined.

[0079] The maximum thickness Tmax of the external electrode 13 means the maximum thickness within the region where the ten-point mean roughness Rz of the electrode formation surface 33 is determined.

[0080] Furthermore, it is preferable that the number of recesses is greater than the number of protrusions in the undulating curve of the electrode formation surface 33. This is because, when the number of recesses is greater than the number of protrusions on the electrode formation surface 33 of the base 11, the number of protrusions of the external electrode 13 filled in the base 11 increases, and the external electrode 13 can be fixed particularly firmly to the base 11, making it difficult for the external electrode 13 to peel off.

[0081] The method for determining whether there are any concave or convex portions is as explained for the ten-point average roughness Rz. The evaluation is performed under the same conditions as for the ten-point average roughness Rz in the same evaluation area, and the number of concave and convex portions can be determined for the waviness curve obtained.

[0082] Furthermore, the electrode formation surface 33 of the base 11 preferably has a ratio of the ten-point average roughness Rz to the arithmetic mean roughness Ra, i.e., Rz / Ra, of 15 or less. By setting Rz / Ra to 15 or less, the sizes of the recesses and protrusions on the electrode formation surface 33 of the base 11 become uniform, allowing the base 11 and the external electrode 13 to be uniformly attached over a wide area. It is more preferable that Rz / Ra is 10 or less.

[0083] The lower limit of Rz / Ra is not particularly limited either, but may be, for example, 5 or more. [Manufacturing method for coil parts] A configuration example of a method for manufacturing a coil component will be described. According to the method for manufacturing a coil component of this embodiment, a coil component according to one aspect of the present disclosure can be manufactured, so some of the matters already explained will not be explained again. Note that the method for manufacturing a coil component described below is merely one configuration example of a method for manufacturing a coil component, and the manufacturing method of a coil component according to one aspect of the present disclosure is not limited to the method for manufacturing a coil component described below.

[0084] The method for manufacturing a coil component of this embodiment can include a compact preparation step (S61), a surface treatment step (S62), and an external electrode formation step (S63), as shown in flow chart 60 in FIG.

[0085] Each step will be explained below with reference to the drawings as necessary. Fig. 7 is a cross-sectional view taken at a position passing through the central axis CA of the coil conductor 12 included in the coil component 10 to be manufactured. The cross-section taken at a position passing through the central axis CA of the coil conductor 12 included in the coil component 10 to be manufactured does not include the lead-out portion 122, but to clarify the operations in the manufacturing process, the lead-out portion 122 is also shown in Fig. 7 by a two-dot chain line. (1) Molded object preparation process In the compact preparation step (S61), a compact can be prepared that includes a substrate containing metal magnetic particles and a binder, and a coil conductor disposed in the substrate.

[0086] In the compact preparation step (S61), it is only necessary to prepare a compact (composite body) including a substrate and a coil conductor, and the specific procedure is not particularly limited.

[0087] The compact preparation step (S61) can include, for example, the following first substrate formation step, coil conductor installation step, second substrate precursor formation step, and polishing step. (1-1) First base formation step In the first substrate forming step, a first substrate can be formed.

[0088] In the first substrate forming step, the first substrate can be formed by compression molding, warm molding, or sheet molding.

[0089] Specifically, in the first substrate formation step, as shown in FIG. 7(A), a first composite magnetic material obtained by kneading a plurality of first metal magnetic particles and a binder can be filled into a molding die 71. The binder can contain a first resin, which is a resin. The first metal magnetic particles and first resin contained in the first composite magnetic material can be suitably the metal magnetic particles and resin that can be contained in the substrate 11 described above, so a description thereof will be omitted here. The first composite magnetic material may contain inorganic particles, etc., as described as being capable of being contained in the substrate 11, as necessary.

[0090] Then, first base 111 can be formed by applying a molding pressure that increases the packing density of the first composite magnetic material at a temperature below the thermosetting temperature of the resin contained in the first composite magnetic material.

[0091] It is noted that the first composite magnetic material may not be completely hardened in the first substrate forming step, but may be hardened in conjunction with forming the second substrate precursor in the second substrate precursor forming step. For this reason, the first substrate forming step can also be called the first substrate precursor forming step, and the first substrate forming step can also be said to form the first substrate precursor. (1-2) Coil conductor installation process In the coil conductor providing step, as shown in FIG. 7(B), the coil conductor 12 can be provided on the first surface 111A of the first base 111 obtained in the first base forming step.

[0092] The coil conductor 12 can be prepared in advance by winding a metal strip around a core using a known winding machine such as a spindle-type winding machine. (1-3) Second base precursor formation step In the second substrate precursor forming step, as shown in FIG. 7(C), a second substrate precursor 72 can be formed so as to cover the first surface 111A of the first substrate 111 and the coil conductor 12.

[0093] In the second substrate precursor forming step, the second substrate precursor can be formed by compression molding, warm molding, or sheet molding.

[0094] Specifically, in the second base precursor forming step, as shown in FIG. 7(C), a second composite magnetic material obtained by kneading a plurality of second metal magnetic particles and a binder can be filled into a molding die 71. The binder can contain a second resin, which is a resin. The second metal magnetic particles and second resin can be suitably the same as those contained in the base 11 described above, and therefore will not be described here. The second composite magnetic material may contain inorganic particles, etc., as necessary, as described as being contained in the base 11. The first composite magnetic material and the second composite magnetic material may be the same or different in the types and compositions of the materials, such as the metal magnetic particles, contained therein.

[0095] Then, by applying a molding pressure that increases the filling rate of the second composite magnetic material at a temperature equal to or higher than the thermosetting temperature of the resin contained in the second composite magnetic material, the second substrate precursor 72 can be formed. When forming the second substrate precursor 72 in the second substrate precursor forming step, it is preferable to select a heating temperature that is equal to or higher than the thermosetting temperature of the resin contained in the first composite magnetic material. By selecting a temperature at which the second substrate precursor 72 is formed in the second substrate precursor forming step that is equal to or higher than the thermosetting temperature of the resin contained in the first composite magnetic material, the resin contained in the first substrate 111 can be cured at the same time as the second substrate precursor 72 is formed.

[0096] The forming mold 71 may be different between the first substrate forming step and the second substrate precursor forming step. In this case, for example, the forming mold can be changed after the first substrate forming step and before the coil conductor providing step.

[0097] Since the excess portion can be removed in the polishing step described below, the second substrate precursor 72 can be formed in a size larger than the target second substrate 112 in the second substrate precursor formation step. (1-4) Polishing process 7(D), in the polishing step, the upper surface of the second substrate precursor 72 in FIG. 7(C), which is the surface opposite to the surface on which the first substrate 111 is arranged, is polished to expose the first lead portion 122A and the second lead portion 122B of the coil conductor 12, thereby preparing the molded body 73 to be subjected to the surface treatment step. By polishing the second substrate precursor 72, the molded body 73 can have a second substrate 112 of a desired size. (2) Surface treatment process (S62) In the surface treatment step (S62), the surface of the base 11 can be treated. Specifically, in the surface treatment step (S62), the surface treatment can be performed on the electrode formation surface 33, which is the surface of the base 11 on which the external electrode 13 is formed and which faces the external electrode 13. In the surface treatment step, the surface treatment can be performed so that the length of the electrode formation surface 33 in a cross section perpendicular to the electrode formation surface 33 is 150% or more of the horizontal projection length of the electrode formation surface 33.

[0098] The specific method for performing the surface treatment in the surface treatment step (S62) is not particularly limited, but for example, one or more methods selected from laser irradiation, blasting, laser processing, polishing, chemical treatment, etc. can be used for the electrode formation surface 33. Parts of the surface of the base 11 where the external electrodes 13 are not to be formed other than the electrode formation surface 33 can be masked with tape, resin, etc. to prevent the surface treatment from being performed.

[0099] When the electrode formation surface 33 is surface treated by sandblasting in the surface treatment step (S62), the resin in the base 11 can be preferentially removed by using particles smaller than the metal magnetic particles contained in the base 11 for the particles to be sprayed onto the base 11. Then, by removing the resin in the base 11, the metal magnetic particles can also be removed. This is preferable because it allows the electrode formation surface 33 of the base 11 to be surface treated efficiently. Note that small particles mean particles that are small when compared with the particle size at 50% of the volume integrated value in the particle size distribution determined by laser diffraction / scattering method.

[0100] After the surface treatment step (S62) is completed, if necessary, abrasives and the like that have adhered to the surface of the substrate 11 during the surface treatment step may be removed using gas or a liquid such as a cleaning liquid. (3) External electrode formation process (S63) In the external electrode forming step (S63), external electrodes 13 electrically connected to coil conductors 12 can be formed on electrode forming surfaces 33 of the surfaces of base body 11.

[0101] In the external electrode formation step (S63), the external electrode 13 can be formed by applying a conductive paste to the electrode formation surface 33 of the base 11. The external electrode 13 can be provided on the surface of the base 11 so as to be electrically connected to the first lead portion 122A and the second lead portion 122B of the coil conductor 12. The external electrode 13 can also have a Ni plating layer, a Sn plating layer, a conductive resin layer, etc.

[0102] In this manner, the coil device 10 can be manufactured. However, the manufacturing method of the coil device 10 is not limited to the above-described manufacturing method. At least one of the first base 111 and the second base 112 may be manufactured by transfer molding or sheet molding instead of compression molding.

[0103] Aspects of the present disclosure are, for example, as follows.

[0104] <1> a substrate containing metal magnetic particles and a binder; a coil conductor disposed in the substrate; an external electrode provided on a surface of the base and electrically connected to the coil conductor; A coil component in which, in a cross section passing through the joint between the base and the external electrode, the length of the electrode formation surface of the base facing the external electrode is 150% or more of the horizontal projection length of the electrode formation surface.

[0105] <2> In a cross section passing through the joint, the length of the electrode-forming surface of the substrate is 200% or more of the horizontal projection length of the electrode-forming surface. <1> The coil component according to claim 1.

[0106] <3> the ten-point average roughness Rz of the electrode formation surface is smaller than the maximum value of the thickness of the external electrodes; <1> or <2> The coil component according to claim 1.

[0107] <4> the number of recesses is greater than the number of protrusions in the undulating curve of the electrode formation surface; <1> from <3> The coil component according to any one of the preceding claims.

[0108] <5> The external electrodes have a structure in which a metal layer and a conductive resin layer are laminated. <1> from <4> The coil component according to any one of the preceding claims.

[0109] <6> a compact preparation step of preparing a compact including a substrate containing metal magnetic particles and a binder and a coil conductor disposed in the substrate; a surface treatment step of performing surface treatment on the substrate; an external electrode forming step of forming an external electrode electrically connected to the coil conductor on an electrode forming surface of the surface of the base, A method for manufacturing a coil component, wherein the surface treatment step is performed such that the length of the electrode formation surface in a cross section of the surface of the base that is perpendicular to the electrode formation surface is 150% or more of the horizontal projection length of the electrode formation surface. [Explanation of symbols]

[0110] 10 Coil parts 11 Base 11a 1st main surface 11b 2nd principal surface 11c 1st end face 11d 2nd end face 11e 1st side 11f 2nd side 111 First base 111A 1st surface 111B 2nd surface 112 Second base 12 Coil conductor 121 Orbital Club 122 Drawer section 122A 1st drawer 122B 2nd drawer 123 1st lap section 124 2nd lap section 13 External electrode 131 Metal layer 132 Conductive resin layer 133 plating layer 20 Circuit Board 21 Mounting board 22 Land Department CA center axis B area 30 Joint 31 Metal magnetic particles 32 Resin 33 Electrode formation surface LA Horizontal projection length of electrode formation surface LB Length of electrode formation surface LB1 Length LB2 Length LB3 Length LB4 Length LB5 Length LB6 Length LB7 Length LB8 Length LB9 Length 60 Flow Diagram S61 Molded object preparation process S62 Surface treatment process S63 Outer conductor forming process 71 Molding mold 72 Second substrate precursor 73 Molded body

Claims

1. a substrate containing metal magnetic particles and a binder; a coil conductor disposed in the substrate; an external electrode provided on a surface of the base and electrically connected to the coil conductor; A coil component, wherein in a cross section passing through the joint between the base and the external electrode, the length of the electrode formation surface of the base facing the external electrode is 150% or more of the horizontal projection length of the electrode formation surface.

2. 2. The coil component according to claim 1, wherein in a cross section passing through the joint, the length of the electrode-forming surface of the base is 200% or more of the horizontally projected length of the electrode-forming surface.

3. 3. The coil component according to claim 1, wherein the ten-point average roughness Rz of the electrode-forming surface is smaller than the maximum value of the thickness of the external electrodes.

4. 3. The coil component according to claim 1, wherein the number of recesses is greater than the number of protrusions in the undulating curve of the electrode formation surface.

5. 3. The coil component according to claim 1, wherein the external electrodes have a structure in which a metal layer and a conductive resin layer are laminated.

6. a compact preparation step of preparing a compact including a substrate containing metal magnetic particles and a binder and a coil conductor disposed in the substrate; a surface treatment step of performing surface treatment on the substrate; an external electrode forming step of forming an external electrode electrically connected to the coil conductor on an electrode forming surface of the surface of the base, In the surface treatment step, the surface treatment is performed so that the length of the electrode formation surface in a cross section of the surface of the base that is perpendicular to the electrode formation surface is 150% or more of the horizontal projection length of the electrode formation surface.

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