Coil component, circuit board, electronic device, and method of manufacturing coil component

Abstract

To reduce stress generated in an external electrode.SOLUTION: A coil component includes: a magnetic base formed by bonding metal magnetic particles with a resin; a conductor provided on at least one of the inside and the surface of the magnetic base; a first conductive resin layer which is provided on a first surface facing the substrate at the time of mounting out of the first surface and a second surface that are adjacent to each other of the magnetic base; a second conductive resin layer which is provided on the second surface and is thinner than the thickness of the first conductive resin layer; and an external electrode which is formed of a metal layer covering the first conductive resin layer and the second conductive resin layer, and is electrically connected to the conductor.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a coil component, a circuit board, an electronic device, and a method for manufacturing a coil component. [Background technology]

[0002] Electronic devices such as communication devices and automotive electrical equipment are becoming increasingly sophisticated, and accordingly, electronic components are being required to be compact as well as highly functional. Furthermore, the range of applications for electronic components is expanding, and as these applications expand, more is being expected of electronic components. In particular, there are increasing demands for electronic components that can withstand harsh environments of temperature and humidity.

[0003] The miniaturization of electronic components is also progressing in coil components. A typical example is a coil component called 0402 size, which is created by forming a laminate using the same lamination process as in multilayer capacitors. On the other hand, coil components made by winding insulated conductors are lagging behind in terms of miniaturization, and one of the constraints on miniaturization is the external electrodes.

[0004] For example, in multilayer inductors, the use of external electrodes that combine a plated layer with a sintered electrode layer allows for a relatively thin thickness, and because the electrode layers are made to contain nothing other than metal, they have low resistance despite their thin thickness.In contrast to this, a representative example of a coil component made with wire that has begun to see widespread use in recent years is the metal composite type, in which a metal magnetic material is solidified with resin.

[0005] For example, Patent Document 1 discloses a resin molded body (component body) containing metallic magnetic powder, combined with a conductive paste in which plating or metal particles such as Au or Ag are dispersed in resin as external electrodes. This is because the resin molded body, which corresponds to the component body, is solidified by resin, and therefore sintered electrode layers such as those used in multilayer inductors cannot be used. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] International Publication No. 2017 / 115604 Summary of the Invention [Problem to be solved by the invention]

[0007] When a conductive paste is used for the external electrodes, the conductive paste must contain a certain amount of resin to ensure adhesion, and the increased resistance caused by the presence of the resin must be compensated for by a certain thickness. These points distinguish external electrodes that use conductive paste from sintered electrode layers. There are also other process-related constraints, but in any case, the external electrodes are one of the constraints on miniaturization of metal composite coil components.

[0008] Furthermore, in miniaturizing coil components, it is necessary to increase the volume of the resin molded body that forms the main body of the component as much as possible, and for this reason, in addition to thinning the external electrodes, the number of surfaces on which the external electrodes are provided is also reduced to one or two surfaces. On the other hand, reducing the surface area on which the external electrodes are provided also reduces the contact area between the external electrodes and the resin molded body, making it even more necessary to achieve both thinner external electrodes and good adhesion. Therefore, an object of the present invention is to reduce the stress generated in the external electrodes, which is one of the causes of reduced adhesion, in order to enable the miniaturization of coil components. [Means for solving the problem]

[0009] In order to solve the above problem, a coil component according to one embodiment of the present invention comprises a magnetic base formed by bonding metal magnetic particles with a resin, a conductor provided on at least one of the interior and surface of the magnetic base, a first conductive resin layer provided on the first surface, of adjacent first and second surfaces of the magnetic base, which faces a substrate when mounted, a second conductive resin layer provided on the second surface and thinner than the first conductive resin layer, and an external electrode formed from a metal layer covering the first conductive resin layer and the second conductive resin layer, and electrically connected to the conductor.

[0010] In a coil component according to one aspect of the present invention, the first conductive resin layer contains a resin at a rate higher than the rate of resin in the second conductive resin layer. In a coil component according to an aspect of the present invention, the first conductive resin layer contains resin at a ratio of 50 vol % or more. In a coil component according to an aspect of the present invention, the first conductive resin layer contains resin in an amount of 60 vol % or more and 75 vol % or less.

[0011] Furthermore, in a coil component according to one aspect of the present invention, the second conductive resin layer is separated into multiple parts when viewed in a cross section in any direction along the front and back surfaces of the second conductive resin layer. In the coil component according to one aspect of the present invention, a portion of the second conductive resin layer reaches the first surface and covers a portion of the first conductive resin layer. In a coil component according to an aspect of the present invention, the second conductive resin layer reaches each ridge line surrounding the second surface.

[0012] In the coil component according to one aspect of the present invention, a portion of the second conductive resin layer extends to a third surface facing away from the first surface. A circuit board according to one aspect of the present invention includes any one of the coil components described above and a substrate on which the coil component is mounted. An electronic device according to an aspect of the present invention includes the circuit board described above.

[0013] Furthermore, a manufacturing method for a coil component according to one embodiment of the present invention is a manufacturing method for manufacturing any of the above coil components, and includes the steps of forming the first conductive resin layer to a thickness greater than the surface roughness Ra1 of the first surface, forming the second conductive resin layer, and forming the metal layer. Furthermore, a manufacturing method for a coil component according to another aspect of the present invention is a manufacturing method for manufacturing any of the above-mentioned coil components, and includes the steps of forming the first conductive resin layer, forming the second conductive resin layer to a thickness smaller than the surface roughness Ra2 of the second surface, and forming the metal layer. [Effects of the Invention]

[0014] According to the present invention, it is possible to reduce the stress generated in the external electrodes. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a perspective view showing a coil component according to an embodiment of the present invention; [Figure 2] FIG. 2 is a side view of the coil device shown in FIG. [Figure 3] FIG. 2 is a cross-sectional view of the coil component shown in FIG. [Figure 4] FIG. 10 is a perspective view showing a modified example of the external electrode. [Figure 5] FIG. 10 is a perspective view showing another modified example of the external electrode. [Figure 6] FIG. 3 is an enlarged view conceptually showing the microscopic structure of a first conductive resin layer. [Figure 7] FIG. 4 is an enlarged view conceptually showing the microscopic structure of a second conductive resin layer. [Figure 8] 10 is an enlarged view conceptually showing a microscopic structure of a modified example of the second conductive resin layer. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the present invention, and not all of the combinations of features described in the embodiments are necessarily essential to the configuration of the present invention. The configuration of the embodiments may be modified or changed as appropriate depending on the specifications of the device to which the present invention is applied and various conditions (such as usage conditions and usage environment).

[0017] The technical scope of the present invention is defined by the claims and is not limited by the following individual embodiments. The drawings used in the following description may differ in scale and shape from the actual structure to make each configuration easier to understand. Components shown in the drawings described earlier may be referenced as appropriate in the description of the drawings that follow.

[0018] <Coil component structure> FIG. 1 is a perspective view showing a coil component according to one embodiment of the present invention. The coil component 1 is mounted on a substrate 2a. The substrate 2a is provided with, for example, two land portions 3. The coil component 1 has one magnetic base 11 and two external electrodes 12. The coil component 1 is mounted on the substrate 2a by joining each external electrode 12 to the land portions 3 with solder. A circuit board 2 according to one embodiment of the present invention includes the coil component 1 and a substrate 2a on which the coil component 1 is mounted. The circuit board 2 can be included in a variety of electronic devices. Examples of electronic devices that include the circuit board 2 include automotive electrical equipment, servers, board computers, and various other electronic devices.

[0019] In this specification, unless otherwise understood in the context, the directions are described based on the "L axis" direction, the "W axis" direction, and the "H axis" direction in Figure 1, and are referred to as the "length" direction, the "width" direction, and the "height" direction, respectively. The "height" direction may also be referred to as the "thickness" direction. The coil component 1 has a rectangular parallelepiped outer shape. That is, the coil component 1 has a first end face 1a and a second end face 1b at both ends in the length direction L, a first main face 1c (top face 1c) and a second main face 1d (bottom face 1d) at both ends in the height direction H, and a front face 1e and a rear face 1f at both ends in the width direction W.

[0020] The dimensions of each side of the rectangular parallelepiped coil component 1 are, for example, 1 to 5 mm in the length direction L, 0.5 to 4.5 mm in the width direction W, and 0.4 to 3.5 mm in the height direction H. The height direction H is smaller than the length direction L, and is further smaller than the width direction W. The first end face 1a, the second end face 1b, the first main face 1c, the second main face 1d, the front face 1e, and the rear face 1f of the coil device 1 may be flat or curved. Furthermore, the eight corners and 12 ridges of the coil device 1 may be rounded.

[0021] In this specification, even when the first end face 1a, the second end face 1b, the first main face 1c, the second main face 1d, the front face 1e, and the rear face 1f of the coil device 1 are partially curved, or when the corners and ridges of the coil device 1 are rounded, such a shape may be referred to as a "rectangular parallelepiped shape." In other words, in this specification, when we refer to a "rectangular parallelepiped" or a "rectangular parallelepiped shape," it does not mean a "rectangular parallelepiped" in the strict mathematical sense.

[0022] Coil component 1 according to one embodiment of the present invention has magnetic substrate 11 and external electrodes 12, and has a conductor inside. Here, magnetic substrate 11 may be what is called a drum core, in which a conductor is wound around the surface of magnetic substrate 11, or may be what has a conductor disposed inside magnetic substrate 11.

[0023] The magnetic substrate 11 is an insulator containing a magnetic material. The magnetic substrate 11 contains 95 wt% or more of a metal magnetic material and 1 wt% or more of a resin, and may also contain other components. The metal magnetic material is metal magnetic particles containing Fe, Ni, or Co. The metal magnetic particles may contain any one of Si, Cr, Al, B, and P in addition to Fe, Ni, and Co, or may contain a combination of Si, Cr, Al, B, and P.

[0024] The magnetic substrate 11 may be formed from a combination of multiple types of metal magnetic particles, or may contain a ceramic material or a glass material. The magnetic substrate 11 is formed by bonding metal magnetic particles with a resin. The metal magnetic particles may be insulated, or the insulation may be ensured by the presence of a resin. Fig. 2 is a side view of the coil device 1 shown in Fig. 1, and Fig. 3 is a cross-sectional view of the coil device 1 shown in Fig. 1. Fig. 3 shows a cross section taken along line BB shown in Fig. 1. The following description will be made with reference to Figs. 1 to 3.

[0025] The magnetic base 11 has a rectangular parallelepiped shape and has end faces 102 at both ends in the length direction L, a bottom face 101 at one end in the height direction H, a top face 103 at the other end in the height direction H, and a front face 104 and a rear face 105 at both ends in the width direction W. The bottom face 101 is the face that faces the substrate 2a when the coil component 1 is mounted on the substrate 2a.

[0026] The conductor 14 is made of a metal material with excellent conductivity. For example, the metal material for the conductor 14 may be one or more of Cu, Al, Ni, or Ag, or an alloy containing any of these metals. An insulating coating may be provided on the surface of the conductor 14. One conductor 14 may be provided for one magnetic base 11, as shown in FIG. 3, or multiple conductors 14 may be provided for one magnetic base 11.

[0027] The conductor 14 shown in Fig. 3 has a winding portion 402 formed by winding a conductor wire around, and an extraction portion 401 that is extracted from the winding portion 402 and connected to the external electrode 12. Fig. 3 shows an example of a so-called horizontally wound winding portion 402 in which the conductor wire is wound along the bottom surface 101 and top surface 103 of the magnetic base 11. The conductor 14 may also have a so-called vertically wound winding portion in which the conductor wire is wound along the end surface 102 of the magnetic base 11.

[0028] The coil component 1 includes external electrodes 12 on the first end face 1a side and the second end face 1b side. In one embodiment of the present invention, each external electrode 12 is provided across a portion of the bottom face 101 of the magnetic base 11 and each end face 102. That is, each external electrode 12 extends over a portion of the bottom face 101 on the first end face 1a side and a portion of the first end face 1a on the bottom face 101 side, and a portion of the bottom face 101 on the second end face 1b side and a portion of the second end face 1b on the bottom face 101 side. Each end face 102 is a surface adjacent to the bottom face 101 and extends in a direction intersecting with the substrate 2a when the coil component 1 is mounted. As described above, the external electrodes 12 are joined to the lands 3 on the substrate 2a with solder 4.

[0029] The external electrode 12 extends over the entire end faces 102. The external electrode 12 extends over each ridge line surrounding the end faces 102, with a portion of the electrode extending over the top face 103; that is, it extends over the bottom face 101, the end faces 102, and a portion of the top face 103 on the end face 102 side. The external electrode 12 also extends over a portion of each of the end faces 102 to the front face 104 and the rear face 105. The external electrode 12 shown in FIG. 1 differs from a so-called five-sided external electrode in that the portions of the electrode 12 that reach the top face 103, the front face 104, and the rear face 105 do not extend over each face but instead extend thinly along the ridge lines of the end faces 102.

[0030] 4 and 5 are diagrams showing modified examples of the external electrode 12. In FIG. The external electrode 12 of the modified example shown in Fig. 4 extends over each end face 102 of the magnetic base 11 and also extends over part of the bottom face 101. Furthermore, the external electrode 12 of the modified example shown in Fig. 4 partially reaches the top face 103, but does not reach the front face 104 or the rear face 105. 5 extends over a portion of each end face 102 of the magnetic base 11 and also over a portion of the bottom face 101. Furthermore, the external electrode 12 of the modified example shown in FIG. 5 does not reach the top face 103, the front face 104, or the rear face 105.

[0031] In this way, the external electrode 12 extends over each end face 102 and the bottom face 101, but does not reach the top face 103, the front face 104, or the rear face 105, or if it does reach them, it extends only in a thin strip along the ridge of each end face 102. The external electrode 12 may extend over the front face 104 and the bottom face 101, and also over the rear face 105 and the bottom face 101.

[0032] <External electrode structure> The coil component 1 of the embodiment shown in FIGS. 1 to 3 will be described below. The external electrode 12 includes a first conductive resin layer 201 provided on the bottom surface 101, a second conductive resin layer 202 provided on the end surface 102, and a metal layer 203 covering the first conductive resin layer 201 and the second conductive resin layer 202. The external electrode 12 may include a third conductive resin layer (not shown) in addition to the first conductive resin layer 201 and the second conductive resin layer 202.

[0033] The first conductive resin layer 201 and the second conductive resin layer 202 are conductive layers containing resin and metal particles. The first conductive resin layer 201 and the second conductive resin layer 202 contain 80 wt% or more of a metal material and 10 wt% or more of a resin, and may also contain other components. The metal material is metal particles containing Ag, Cu, and Ni, and may also contain a ceramic material or a glass material. The conductive resin layer obtains conductivity by bonding the metal particles with resin and by the presence of portions where the metal particles are continuously connected.

[0034] The metal layer 203 is made of a metal material with excellent conductivity. Examples of metal materials that can be used include Cu and Ag, and also Ni, Pd, and Sn. The metal layer 203 is formed in a layered structure by overlapping layers made primarily of each metal material or layers that are partially alloyed with each other. The metal layer 203 can be formed by, for example, plating, applying a metal material, sputtering, or vapor deposition.

[0035] The external electrode 12 is provided on the surface of the magnetic base 11, and electrical conduction is achieved at the location where it is connected to the lead-out portion 401 of the conductor 14. At this location, the lead-out portion 401 of the conductor 14 and the external electrode 12 are connected via a part of the layer containing Sn. 3, in this embodiment, the conductor 14 and the external electrode 12 are connected to each other on the bottom surface 101 between the lead-out portion 401 and the first conductive resin layer 201, thereby achieving electrical continuity. In this case, electrical continuity is reliably maintained by using the first conductive resin layer 201, which has the effect of alleviating stress, as will be described later.

[0036] The external electrode 12 may have a base electrode layer (not shown) between the first conductive resin layer 201 or the second conductive resin layer 202 and the magnetic base 11. The base electrode layer is made of a metal material such as Ag, Cu, Ti, or Ni. The base electrode layer is provided on the surface of the magnetic base 11 by plating, applying a metal material, sputtering, or vapor deposition. The base electrode layer may have a thickness of 1 μm or less, and a portion of the layer may be separated from other portions.

[0037] 3, the first conductive resin layer 201 extends over a portion of the bottom surface 101 that is close to the end surface 102. The second conductive resin layer 202 extends over the entire end surface 102, reaching each ridge line that surrounds the end surface 102. By having the second conductive resin layer 202 extend over the entire end surface 102, the impact on the external dimensions of the coil component 1 is reduced, while the contact area between the magnetic base 11 and the external electrode 12 is increased, improving the adhesion between the magnetic base 11 and the external electrode 12.

[0038] Furthermore, a portion of the second conductive resin layer 202 reaches the bottom surface 101, and the second conductive resin layer 202 covers a portion of the first conductive resin layer 201 near the ridge line between the bottom surface 101 and the end surface 102. Covering a portion of the first conductive resin layer 201 near the ridge line is preferable because it allows continuous external electrodes 12 to be formed even in the ridge line portion without increasing the thickness of the metal layer 203. The second conductive resin layer 202 may be in contact with the first conductive resin layer 201 without covering it, or the second conductive resin layer 202 may be spaced apart from the first conductive resin layer 201.

[0039] 1 to 3, a portion of the second conductive resin layer 202 reaches the upper surface 103. By having a portion of the second conductive resin layer 202 reach the upper surface 103, the contact area between the magnetic base 11 and the external electrodes 12 is increased while the effect on the external dimensions of the coil component 1 is suppressed, thereby improving the adhesion between the magnetic base 11 and the external electrodes 12. Furthermore, the magnetic base 11 can withstand stress from multiple directions, improving durability.

[0040] 1 to 3, a portion of the second conductive resin layer 202 reaches the front surface 104 and the rear surface 105. The area of ​​the portion of the second conductive resin layer 202 that reaches the top surface 103, the front surface 104, and the rear surface 105 is 50% or less, or 25% or less, of the area of ​​the first conductive resin layer 201 that extends to the bottom surface 101.

[0041] 6 is an enlarged view conceptually showing the microscopic structure of the first conductive resin layer 201. FIG. 7 is an enlarged view conceptually showing the microscopic structure of the second conductive resin layer 202. The bottom surface 101 and the end surface 102 have a microscopic uneven structure caused by the metal magnetic particles 106. The first conductive resin layer 201 and the second conductive resin layer 202 are then provided on the uneven structure.

[0042] The thickness d1 of the first conductive resin layer 201 is greater than the thickness d2 of the second conductive resin layer 202. This thickness relationship (d1>d2) provides a buffering effect between the coil component 1 and the substrate 2a. Furthermore, this thickness relationship makes it possible to miniaturize the coil component 1 without providing unnecessary thickness to portions other than the bottom surface 101. Note that the thicknesses d1 and d2 are thicknesses extending from the magnetic base 11 outward in a direction perpendicular to the magnetic base 11, and for example, the maximum thickness of each layer is used as a representative value for the thicknesses d1 and d2. Regarding metal layer 203 formed to cover first conductive resin layer 201 and second conductive resin layer 202, a Ni layer is more likely to cause stress than a Sn layer. By providing a thick first conductive resin layer 201 and obtaining a buffering effect against stress, it becomes possible to employ metal layer 203 having a Ni layer with sufficient thickness.

[0043] In this embodiment, the proportion of resin in the first conductive resin layer 201 is higher than the proportion of resin in the second conductive resin layer 202. Therefore, the effect of stress relaxation in the first conductive resin layer 201 is improved compared to when the resin proportions are the same. Specifically, the resin content in the first conductive resin layer 201 is 50 vol% or more. Alternatively, the resin content in the first conductive resin layer 201 is 60 vol% or more and 75 vol% or less. Furthermore, the resin content in the second conductive resin layer 202 is 40 vol% or more. Alternatively, the resin content in the second conductive resin layer 202 is 50 vol% or more and 60 vol% or less.

[0044] When the resin ratio in the first conductive resin layer 201 is within the above-mentioned specific numerical range, the effect of stress relaxation in the first conductive resin layer 201 is further improved. The presence and thickness of each layer forming the external electrode 12 can be confirmed by observing a cross section of the external electrode 12 using an SEM or the like. For example, SEM observation can confirm the presence of each contact surface that distinguishes between the magnetic base 11, the conductor 14, the conductive resin layers 201 and 202, and the metal layer 203. Furthermore, component analysis using SEM can confirm the presence of metal, carbon, and oxygen, thereby distinguishing each layer.

[0045] <Coil component manufacturing process> The manufacturing process for the coil component 1 may be a manufacturing process in which the magnetic base 11, the conductor 14, and the external electrode 12 are produced in this order, or alternatively, the magnetic base 11, the conductor 14, a portion of the external electrode 12, and the remaining portion of the external electrode 12 are produced in this order. A method for manufacturing the metal composite type coil component 1 will be described below as a representative manufacturing method.

[0046] The metal composite type coil component 1 is a product in which a conductor 14 is sealed with a composite magnetic material containing metal magnetic particles and resin to form a magnetic base 11, and an external electrode 12 is provided on the magnetic base 11. The conductor 14 may be made using a conducting wire with an insulating coating, or may be made by a method in which a conductor is provided on an insulator by plating.

[0047] The composite magnetic material is molded into a compact by applying pressure and temperature. At this molding stage, the conductor 14 is integrated with the composite magnetic material. Specific pressure and temperature during molding are, for example, 10 to 100 MPa and 100 to 200°C. The compact is heated to 150 to 200°C, and the resin of the composite magnetic material is cured to form the magnetic base 11.

[0048] The magnetic base 11 is also subjected to individual division and surface treatment, and the ends of the conductors 14 are exposed on the surface of the magnetic base 11. The ends of the conductors 14 are also subjected to surface treatment. For example, dust and oxides are removed from the ends of the conductors 14 by etching or plasma treatment, and a metal surface necessary for connection to the external electrodes 12 is obtained for the ends.

[0049] A conductive paste is applied to the surface of magnetic base 11 where the end of conductor 14 exists by screen printing, transfer, dipping, or the like. For example, the conductive paste is applied to bottom surface 101 by screen printing to a thickness of 10 to 30 μm, and the conductive paste is applied to end surface 102 by transfer or dipping to a thickness of 10 μm or less. For example, a step of removing excess conductive paste may be added to adjust the thickness.

[0050] The conductive paste provided on bottom surface 101 and end surface 102 is subjected to, for example, a low-temperature heat treatment to obtain first conductive resin layer 201 and second conductive resin layer 202. The conductive paste provided on bottom surface 101 is provided to a sufficient thickness so that the thickness of first conductive resin layer 201 is greater than the surface roughness Ra1 of bottom surface 101.

[0051] The conductive paste used for the bottom surface 101 and the end surface 102 may be made of the same ingredients. Alternatively, conductive paste containing metal particles with different particle sizes may be used to adjust the thickness of the conductive paste on each surface. For example, to reduce the thickness of the conductive paste, it is advisable to select a particle size that corresponds to the surface roughness Ra of the magnetic base 11. In other words, by using a conductive paste containing metal particles with a particle size smaller than the surface roughness Ra, a thickness that corresponds to the unevenness of the surface of the magnetic base 11 can be obtained. In particular, the thickness of the conductive paste becomes thinner when the proportion of metal particles with a particle size of 1 μm or less is high.

[0052] Furthermore, when the conductive paste is applied to the entire surface of the end face 102 by transfer or the like, it tends to spread wetly onto the surfaces adjacent to the end face 102 (i.e., the top surface 103, the front surface 104, and the rear surface 105), so that the thickness is thin on the end face 102 and the area present on the adjacent surfaces can be limited to a small area. Furthermore, a base electrode layer may be formed by plating or sputtering before the conductive paste is applied. If a base electrode layer is formed, it becomes possible to form the metal layer 203 over the entire required area in the subsequent formation of the metal layer 203, even if the thickness of the conductive paste is thinner.

[0053] After the first conductive resin layer 201 and the second conductive resin layer 202 are obtained by the above process, a metal layer 203 is formed on the first conductive resin layer 201 and the second conductive resin layer 202 by, for example, plating, applying a metal material, sputtering, or vapor deposition. Through the manufacturing process described above, an external electrode 12 having a first conductive resin layer 201 and a second conductive resin layer 202 with the structure shown in Figures 6 and 7 is obtained, and the coil component 1 shown in Figures 1 to 3 is completed.

[0054] FIG. 8 is an enlarged view conceptually showing the microscopic structure of a modified example of the second conductive resin layer 202. In FIG. 8, the second conductive resin layer 202 is separated into a plurality of layer portions 225 in cross section. The cross section may be a cross section in any direction along the front and back surfaces (i.e., the front surface or the back surface) of the second conductive resin layer 202. Therefore, the plurality of layer portions 225 separated from one another in cross section may be separated from one another by grooves, may be partially separated by notches, or may be actually connected by merely having holes between them.

[0055] 8, between the plurality of layer portions 225, the convex portions in the concave-convex structure of the end face 102 protrude from the back surface side to the front surface side of the second conductive resin layer 202. Note that there may be gaps between the plurality of layer portions 225, or the metal layer 203 may be embedded from the front surface side to the back surface side of the second conductive resin layer 202.

[0056] By separating the second conductive resin layer 202 into a plurality of layer portions 225 in any cross section, the thickness of the second conductive resin layer 202 becomes thinner, and the thickness as the external electrode 12 becomes thinner without excessively protruding beyond the outer dimensions of the magnetic base 11. Furthermore, the stress generated in the second conductive resin layer 202 itself becomes smaller, and the stress that the second conductive resin layer 202 receives from the metal layer 203 is also dispersed. Furthermore, the metal layer 203 has a high metal filling rate. The presence of the metal layer 203 with a high filling rate reduces defects and stably maintains the shape of the external electrodes during mounting.

[0057] The second conductive resin layer 202 separated into multiple layer portions 225 can be realized by adding a step of adjusting the thickness of the conductive paste to be thinner in the step of applying the conductive paste to the end face 102. That is, by making the thickness of the conductive paste smaller than the surface roughness Ra2 on the end face 102, portions where metal particles of the conductive paste are present and portions where they are not are formed.

[0058] As a result, holes, grooves, or notches are formed in second conductive resin layer 202 obtained from the conductive paste, and second conductive resin layer 202 naturally has a structure in which it is separated into multiple layer portions 225 at any cross section. Note that the conductive paste provided on end face 102 may be provided directly by printing or the like to a thickness smaller than the surface roughness Ra2 of end face 102, without the step of adjusting the thickness to be thinner. [Explanation of symbols]

[0059] 1 Coil parts 2 Circuit Boards 2a board 3 Land Department 4. Solder 11 Magnetic substrate 12 External electrode 14 Conductors 101 bottom 102 End face 103 Top surface 104 Front 105 Rear 201 First conductive resin layer 202 Second conductive resin layer 203 metal layer

Claims

1. a magnetic substrate formed by bonding metal magnetic particles with a resin; a conductor provided inside or on the surface of the magnetic substrate; a first conductive resin layer provided on the first surface, of which the magnetic base has a first surface and a second surface adjacent to each other and which faces a substrate when mounted; a second conductive resin layer provided on the second surface and thinner than the first conductive resin layer; and an external electrode formed from a metal layer covering the first conductive resin layer and the second conductive resin layer, and electrically connected to the conductor; The coil component is characterized in that the second conductive resin layer is separated into a plurality of portions when viewed in any cross section perpendicular to the second surface.

2. The coil component according to claim 1 , wherein the first conductive resin layer contains a resin at a rate higher than the rate of resin in the second conductive resin layer.

3. 3. The coil component according to claim 1, wherein the first conductive resin layer contains resin at a ratio of 50 vol % or more.

4. 4. The coil component according to claim 3, wherein the ratio of the resin in the first conductive resin layer is 60 vol % or more and 75 vol % or less.

5. The coil component according to claim 1 , wherein a portion of the second conductive resin layer reaches the first surface and covers a portion of the first conductive resin layer.

6. The coil component according to claim 1 , wherein the second conductive resin layer extends over the entire second surface and reaches each ridge line surrounding the second surface.

7. The coil component according to claim 1 , wherein a portion of the second conductive resin layer reaches a third surface facing opposite to the first surface.

8. The coil component according to any one of claims 1 to 7; a substrate on which the coil component is mounted; A circuit board comprising:

9. An electronic device comprising the circuit board according to claim 8.

10. A manufacturing method for manufacturing the coil component according to any one of claims 1 to 7, comprising: forming the first conductive resin layer to a thickness greater than the surface roughness Ra1 of the first surface; forming the second conductive resin layer; forming the metal layer; A method for manufacturing a coil component, comprising:

11. A manufacturing method for manufacturing the coil component according to any one of claims 1 to 7, comprising: forming the first conductive resin layer; forming the second conductive resin layer to a thickness smaller than the surface roughness Ra2 of the second surface; forming the metal layer; A method for manufacturing a coil component, comprising:

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