Electronic component and method for manufacturing the same

Abstract

To provide an electronic component capable of suppressing the migration of impurity atoms between a conductor and an external electrode.SOLUTION: A coil component 1, which is an electronic component, has a base 10, a conductor 25, an external electrode 21 electrically connected to one end of the conductor 25, an external electrode 22 electrically connected to the other end of the conductor 25, a first film 23 located between one end of the conductor 25 and the external electrode 21, and a second film located between the other end of the conductor 25 and the external electrode 22, and the diffusion rate in the first film 23 and the second film is slower than that in the external electrodes 21 and 22.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The disclosure of this specification relates to electronic components and a method for manufacturing electronic components.

Background Art

[0002] As an electronic component, a coil component such as an inductor is known. A conventional coil component typically includes a magnetic substrate made of a magnetic material, a conductor provided in the magnetic substrate and wound around a coil axis, and an external electrode connected to an end of the conductor. This coil component is mounted by electrically connecting the external electrode and a substrate using, for example, solder, and is used as a component of various electronic devices. Conventional coil components are disclosed in, for example, Patent Document 1.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Between the conductor and the external electrode of the electronic component, migration of impurity atoms contained in solder or the like may occur due to, for example, application of heat or voltage. When migration occurs, voids are formed in the conductor and / or the external electrode by alloying of the impurity atoms and the material constituting the conductor or the external electrode. As a result, there is a problem that the bonding strength between the conductor and the external electrode decreases.

[0005] One object of the present invention is to provide an electronic component and a method for manufacturing an electronic component capable of suppressing migration of impurity atoms between a conductor and an external electrode. Other objects of the present invention will be clarified through the description of the entire specification.

Means for Solving the Problems

[0006] An electronic component according to an embodiment of the present invention includes a substrate, a conductor provided inside or outside the substrate, a first external electrode and a second external electrode electrically connected to the conductor, a first film positioned between an end portion of the conductor electrically connected to the first external electrode and the first external electrode, and a second film positioned between an end portion of the conductor electrically connected to the second external electrode and the second external electrode. The diffusion rates in the first film and the second film are slower than the diffusion rates in the first external electrode and the second external electrode.

[0007] In an embodiment of the present invention, the thickness of the first film and the thickness of the second film may be 10 nm or more and 200 nm or less.

[0008] In an embodiment of the present invention, the first film and the second film may be oxide films.

[0009] In an embodiment of the present invention, the first film and the second film may be oxides of a metal material having an ionization tendency the same as or smaller than the ionization tendency of the material constituting the conductor.

[0010] In an embodiment of the present invention, the first film and the second film may be nitride films, carbide films, or oxynitride films (oxynitrides).

[0011] In an embodiment of the present invention, the first film and the second film may be amorphous.

[0012] In an embodiment of the present invention, the unevenness at the interface between the first film and the first external electrode and the unevenness at the interface between the second film and the second external electrode may be greater than the unevenness on the surfaces of the first external electrode and the second external electrode.

[0013] In an embodiment of the present invention, the conductor may include a portion wound around the coil axis.

[0014] One embodiment of the present invention relates to a circuit board including any of the above coil components. Another embodiment of the present invention relates to an electronic device including the above circuit board.

[0015] A method for manufacturing an electronic component according to an embodiment of the present invention is a method for manufacturing a coil component including a base body, a conductor provided inside or outside the base body, and a first external electrode and a second external electrode electrically connected to the conductor. The method includes: a first step of disposing a first end portion of the conductor electrically connected to the first external electrode and a second end portion of the conductor electrically connected to the second external electrode on the surface of the base body; a second step of forming a first film electrically connected to the first end portion and a second film electrically connected to the second end portion; and a third step of forming a first external electrode electrically connected to the first film and a second external electrode electrically connected to the second film. In the second step, the first film and the second film are formed using a material having a diffusion rate slower than the diffusion rate of the material constituting the first external electrode and the second external electrode.

Advantages of the Invention

[0016] According to the present invention, there are provided an electronic component and a method for manufacturing an electronic component capable of suppressing migration of impurity atoms between a conductor and an external electrode.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0018] Hereinafter, various embodiments of the present invention will be described with reference to the drawings as appropriate. Note that the same reference numerals are given to common components in a plurality of drawings. It should be noted that each drawing is not necessarily drawn to an exact scale for convenience of explanation.

[0019] With reference to FIG. 1, an overview of a coil component 1, which is an electronic component according to an embodiment of the present invention, will be described. FIG. 1 is a perspective view schematically showing the coil component 1. As shown in FIG. 1, the coil component 1 includes a base body 10, a coil conductor 25 provided inside the base body 10, an external electrode (first external electrode) 21 provided on the surface of the base body 10, and an external electrode (second external electrode) 22 provided at a position on the surface of the magnetic base body 10 and separated from the external electrode 21.

[0020] In this specification, unless otherwise understood from the context, the “length” direction, “width” direction, and “thickness” direction of the coil component 1 are the “L-axis” direction, “W-axis” direction, and “T-axis” direction in FIG. 1, respectively. The “thickness” direction may also be referred to as the “height” direction.

[0021] The coil component 1 is mounted on a circuit board (not shown). Two land portions are provided on this circuit board. The coil component 1 can be mounted on the circuit board by joining the external electrodes 21 and 22 and the land portions corresponding to the external electrodes 21 and 22, respectively. Electronic devices on which this circuit board can be mounted include smartphones, tablets, game consoles, and various other electronic devices. This circuit board may be mounted on an electrical component of an automobile, which is a type of electronic device.

[0022] The coil component 1 can be applied to inductors, transformers, filters, reactors, and various other coil components. The coil component 1 can also be applied to coupling inductors, choke coils, and various other magnetically coupled coil components. The uses of the coil component 1 are not limited to those specified in this specification.

[0023] The base body 10 is made of an insulating material. In one embodiment, the magnetic base body 10 is mainly made of a magnetic material and is formed in a rectangular parallelepiped shape. The base body 10 of the coil component 1 according to one embodiment of the present invention is formed such that the length dimension (dimension in the L-axis direction) is 1.0 mm to 4.5 mm, the width dimension (dimension in the W-axis direction) is 0.5 mm to 3.2 mm, and the height dimension (dimension in the T-axis direction) is 0.5 mm to 5.0 mm. The dimensions of the base body 10 are not limited to the dimensions specifically described in this specification. In this specification, when referring to a "rectangular parallelepiped" or "rectangular parallelepiped shape", it does not mean only a "rectangular parallelepiped" in a strictly mathematical sense.

[0024] The base body 10 has a first main surface 10a, a second main surface 10b, a first end surface 10c, a second end surface 10d, a first side surface 10e, and a second side surface 10f. The outer surface of the base body 10 is defined by these six surfaces. The first main surface 10a and the second main surface 10b respectively form the surfaces at both ends in the height direction, the first end surface 10c and the second end surface 10d respectively form the surfaces at both ends in the length direction, and the first side surface 10e and the second side surface 10f respectively form the surfaces at both ends in the width direction.

[0025] As shown in FIG. 1, since the first main surface 10a is on the upper side of the magnetic base body 10, the first main surface 10a may be referred to as the "upper surface". Similarly, the second main surface 10b may be referred to as the "lower surface". Since the coil component 1 is arranged such that the first main surface 10a faces the circuit board, the first main surface 10a may also be referred to as the "mounting surface". When referring to the vertical direction of the coil component 1, the vertical direction in FIG. 1 is used as a reference.

[0026] Next, the magnetic substrate 10 will be further described with reference to FIG. 2. FIG. 2 is an enlarged cross-sectional view schematically showing an enlarged cross-section of the substrate 10. As shown in the figure, the substrate 10 includes a plurality of first metal magnetic particles 11, a plurality of second metal magnetic particles 12, and a binder 13. The binder 13 binds the plurality of first metal magnetic particles 11 and the plurality of second metal magnetic particles 12 to each other. In other words, the substrate 10 is composed of the binder 13 and the plurality of first metal magnetic particles 11 and the plurality of second metal magnetic particles 12 bound by the binder 13.

[0027] The plurality of first metal magnetic particles 11 have an average particle size larger than that of the plurality of second metal magnetic particles 12. That is, the average particle size of the plurality of first metal magnetic particles 11 (hereinafter referred to as the first average particle size) and the average particle size of the plurality of second metal magnetic particles 12 (hereinafter referred to as the second average particle size) are different. The first average particle size is, for example, 30 μm, and the second average particle size is, for example, 0.1 μm, but they may have different average particle sizes respectively. In one embodiment of the present invention, the magnetic substrate 10 may further include a plurality of third metal magnetic particles (hereinafter, the average particle size of the third metal magnetic particles is referred to as the third average particle size) having an average particle size different from the first average particle size and the second average particle size. The third average particle size may be smaller than the first average particle size and larger than the second average particle size, or may be smaller than the second average particle size. In the following description, in this specification, when it is not necessary to distinguish the first metal magnetic particles 11, the second metal magnetic particles 12, and the third metal magnetic particles from each other, the first metal magnetic particles 11, the second metal magnetic particles 12, and the third metal magnetic particles included in the magnetic substrate 10 may be collectively referred to as "metal magnetic particles".

[0028] The first metal magnetic particles 11 and the second metal magnetic particles 12 are made of various soft magnetic materials. The first metal magnetic particles 11 are mainly composed of, for example, Fe. Specifically, the first metal magnetic particles 11 are (1) metal particles such as Fe and Ni, (2) crystalline alloy particles such as Fe-Si-Cr alloy, Fe-Si-Al alloy, and Fe-Ni alloy, (3) amorphous alloy particles such as Fe-Si-Cr-B-C alloy and Fe-Si-Cr-B alloy, or (4) mixed particles in which these are mixed. The composition of the metal magnetic particles contained in the magnetic substrate 10 is not limited to the above. The first metal magnetic particles 11 contain, for example, 85 wt% or more of Fe. Thereby, a magnetic substrate 10 having excellent magnetic permeability can be obtained. The composition of the second metal magnetic particles 12 may be the same as or different from the composition of the first metal magnetic particles 11. When the magnetic substrate 10 contains a plurality of third metal magnetic particles (not shown), the composition of the third metal magnetic particles may be the same as or different from the composition of the first metal magnetic particles 11, similar to the composition of the second metal magnetic particles 12.

[0029] The surface of the metal magnetic particles may be coated with an insulating film (not shown). For example, this insulating film is formed from glass, resin, or other materials with excellent insulation properties. This insulating film is formed, for example, on the surface of the first metal magnetic particles 11 by mixing the first metal magnetic particles 11 and glass material powder in a friction mixer (not shown). The insulating film formed from the glass material adheres to the surface of the first metal magnetic particles 11 by compression friction action in the friction mixer. The glass material may contain ZnO and P 2 O 5 and may contain. This insulating film can be formed from various glass materials. The insulating film 14 may be formed from alumina powder, zirconia powder, or other powders of oxides with excellent insulation properties instead of or in addition to the glass powder. The thickness of the insulating film is, for example, 100 nm or less.

[0030] The second metal magnetic particles 12 may be coated with an insulating film different from the insulating film of the first metal magnetic particles 11. This insulating film may be an oxide film formed by oxidation of the second metal magnetic particles 12. The thickness of this insulating film is, for example, 20 nm or less. This insulating film may be an oxide film formed on the surface of the second metal magnetic particles 12 by heat-treating the second metal magnetic particles 12 in an atmospheric atmosphere. This insulating film may be an oxide film containing oxides of Fe and elements contained in the second metal magnetic particles other than this. This insulating film may be an iron phosphate film formed on the surface of the second metal magnetic particles 12 by putting the second metal magnetic particles 12 into phosphoric acid and stirring. The insulating film of the first metal magnetic particles 11 may be an oxide film formed by oxidation of the first metal magnetic particles 11, and the insulating film of the second metal magnetic particles 12 may be a separately provided coating film not depending on the oxidation of the second metal magnetic particles 12.

[0031] The binder 13 is, for example, a thermosetting resin excellent in insulation. For the binder 13, for example, an epoxy resin, a polyimide resin, a polystyrene (PS) resin, a high-density polyethylene (HDPE) resin, a polyoxymethylene (POM) resin, a polycarbonate (PC) resin, a polyvinylidene fluoride (PVDF) resin, a phenolic resin, a polytetrafluoroethylene (PTFE) resin, or a polybenzoxazole (PBO) resin can be used. Also, glass or the like may be used as the binder 13, and the binder 13 may contain an insulating filler or the like.

[0032] The conductor 25 is formed so as to have a predetermined pattern. In the illustrated embodiment, the conductor 25 is wound around the coil axis Ax (see FIG. 1). The conductor 25 has, for example, a spiral shape, a meander shape, a linear shape, or a shape combining these in a plan view.

[0033] The conductor 25 is formed by plating from Cu, Ag, or other conductive materials. The entire surface of the conductor 25 other than the end faces 25a2 and 25b2 may be covered with an insulating film. When the conductor 25 is wound around the coil axis Ax in a plurality of turns as shown in the figure, each turn of the conductor 25 may be spaced apart from other adjacent turns. In this case, the substrate 10 is interposed between adjacent turns.

[0034] The conductor 25 has a lead-out conductor 25a1 at one end thereof (i.e., the end electrically connected to the external electrode 22), and a lead-out conductor 25b1 at the other end thereof (i.e., the end electrically connected to the external electrode 21). An end face 25a2 is formed at the end of the lead-out conductor 25a1, and an end face 25b2 is formed at the end of the lead-out conductor 25b1. The lead-out conductor 25a1, which is one end of the conductor 25, is electrically connected to the external electrode 21, and the lead-out conductor 25b1, which is the other end of the conductor 25, is electrically connected to the external electrode 22.

[0035] In one embodiment of the present invention, the external electrode 21 is provided on a part of the first main surface 10a, the second main surface 10b, the second end face 10c, the first side face 10e, and the second side face 10f of the substrate 10. The external electrode 22 is provided on a part of the first main surface 10a, the second main surface 10b, the second end face 10d, the first side face 10e, and the second side face 10f of the substrate 10. The external electrode 21 and the external electrode 22 are arranged to be spaced apart from each other. The shapes and arrangements of the external electrodes 21 and 22 are not limited to the illustrated examples. The lead-out conductor 25a1 and the lead-out conductor 25b1 are each drawn out to the first main surface (i.e., the mounting surface) 10a of the substrate 10, and the end face 25a2 of the lead-out conductor 25a1 and the end face 25b2 of the lead-out conductor 25b1 are exposed from the substrate 10 on the first main surface 10a. That is, the end face 25a2 of the lead-out conductor 25a1 and the end face 25b2 of the lead-out conductor 25b1 are exposed from the substrate 10 on the same surface. The end face 25a2 of the lead-out conductor 25a1 and the end face 25b2 of the lead-out conductor 25b1 may be exposed from the substrate 10 on different surfaces.

[0036] The external electrodes 21 and 22 may be entirely made of metal or may contain materials other than metal such as resin in part. An example of containing a material other than metal such as resin in part is a conductive resin film. In the illustrated embodiment, the external electrodes 21 and 22 are conductive resin films containing a metal filler F and a conductive resin R (see FIG. 4). The metal filler F may include a first metal filler F1 having a relatively small particle size and a second metal filler having a relatively large particle size. The average particle size of the first metal filler F1 is about 0.1 μm to 2.0 μm, and the average particle size of the second metal filler F2 is about 2.0 μm to 15 μm. The first metal filler F1 and the second metal filler F2 are composed of, for example, Ag. The metal filler F may be a filler of one size. A plating layer may be provided on the surface of this conductive resin film, for example. The plating layer may be, for example, a single-layer plating layer such as a Ni plating layer or a Sn plating layer, or a plating layer composed of a nickel plating layer and a tin plating layer formed on the nickel plating layer.

[0037] FIG. 3 is an enlarged cross-sectional view showing an enlarged cross-section of the periphery of the joint portion between one end of the conductor 25 of the coil component 1 in FIG. 1 and the external electrode 21. As shown in FIG. 3, the coil component 1 has a first film 23 located between the external electrode 21 and one end of the conductor 25 (that is, the lead-out conductor 25a1). That is, the external electrode 21 and one end of the conductor 25 are electrically connected via the first film 23. Further, the coil component 1 has a second film (not shown) located between the external electrode 22 and the other end of the conductor 25 (that is, the lead-out conductor 25b1). In the illustrated embodiment, the first film 23 and the second film have the same function and shape and are composed of the same material. In the following description, unless otherwise specified, the description of the first film 23 is also applied to the second film. Further, although FIGS. 3 and 4 are diagrams for explaining the first film 23, they are also applied to the second film.

[0038] The first film 23 is between the end of the conductor 25 (i.e., the lead-out conductor 25a1) and the external electrode 21, and the end of the conductor 25 and the external electrode 21 are electrically connected via the first film 23. The first film 23 does not have to be in physical contact with the end of the conductor 25 and the external electrode 21 as long as the end of the conductor 25 and the external electrode 21 are electrically conductive. Between the end of the conductor 25 and the external electrode 21, in addition to the first film 23, there may be other layers or films made of materials with excellent conductivity. The first film 23 is composed of a material having a diffusion rate significantly slower than the diffusion rate in the material constituting the external electrode 21. In the illustrated embodiment, the first film 23 is an oxide film. More specifically, the first film 23 is an oxide film of a metal material having an ionization tendency the same as or smaller than the ionization tendency of the material constituting the conductor 25. That is, the first film 23 in the illustrated embodiment is a metal oxide film. As an example, when the conductor 25 is made of copper, the material constituting the first film 23 can be copper oxide such as CuO or Cu 2 O. The material constituting the first film 23 is not limited to the oxide of a metal material. For example, it may be an oxide of Si, an oxide of valve metals such as Fe, Ag, Sn, Cr, Zn, Al, Ti, Ta, Nb, Zr, Hf, Ru, In, Ga, Ge, etc., or an oxide of an alloy containing these valve metals. Further, the first film 23 is not limited to an oxide film and may be a nitride film, a carbide film, or an oxynitride film. Examples of the nitride film include TiN, TaN, FeN, SiN, AlN, etc. Examples of the carbide film include SiC, FeC, WC, diamond-like carbon, diamond, etc. Examples of the oxynitride film include TaON, etc. The materials constituting the first film 23 and the second film are not limited to one type, and the first film 23 and the second film may be constituted by a plurality of types of materials. Generally, compared with the metal material constituting the external electrode 21, the diffusion rates of the materials of the oxide, nitride film, carbide film, and oxynitride film of the above metal material constituting the first film 23 are orders of magnitude slower, and the migration of impurity atoms can be greatly suppressed.

[0039] At least a part of the first film 23 and one end of the conductor 25 (that is, the end face 25a2 of the lead-out conductor 25a1) are connected by an ionic bond. Here, "at least a part" means any region of the end face 25a2. For example, the first film 23 and the end 25a1 may be connected by an ionic bond at the peripheral edge PP (see FIG. 3) of the end face 25a2. FIG. 3 shows an example in which the first film 23 and the end 25a1 of the conductor 25 are connected by an ionic bond over the entire surface of the end face 25a2. In the example of FIG. 3, the first film 23 and the end 25a1 are also ionically bonded at the peripheral edge PP of the end face 25a2.

[0040] As shown in FIG. 4, a plurality of irregularities are formed at the interface between the first film 23 and the external electrode 21, and the irregularities at the interface between the first film 23 and the external electrode 21 are larger than the irregularities on the surface of the external electrode 21. The irregularities at the interface between the first film 23 and the external electrode 21 are formed, for example, by an oxidation reaction on the surface of the first film 23.

[0041] The thickness T of the first film 23 is 10 nm or more and 200 nm or less. In this specification, the thickness T of the first film 23 refers to the dimension in the direction perpendicular to the interface between the first film 23 and the end 25a1 of the conductor 25. When the thickness T of the first film 23 is 200 nm or less, a Schottky current flows through the first film 23, so that an electrical connection between the external electrode 21 and one end of the conductor 25 can be maintained. More preferably, the thickness T of the first film 23 is 50 nm or less. When the thickness T of the first film 23 is 50 nm or less, a tunnel current flows through the first film 23, so that the electrical resistance between the external electrode 21 and one end of the conductor 25 can be further reduced.

[0042] Next, a method for manufacturing the coil component 1 as an electronic component will be described. First, a mixed resin composition prepared by kneading a conductor 25 formed in a coil shape from a metal material or the like, a particle group containing first metal magnetic particles 11 and second metal magnetic particles 12, and a binder 13 made of resin or the like is placed in a molding die, and compression molding is performed such that the end faces 25a2 of the lead-out conductor 25a1 of the conductor 25 and the end faces 25b2 of the lead-out conductor 25b1 are exposed on the surface. The conductor 25 formed in a coil shape is, for example, one formed by winding a conducting wire in a spiral shape, but in addition to winding, it may be a planar coil, and the coil shape is not particularly limited. The conductor 25 can also have an insulating coating. By curing the resin in the molded body, a magnetic substrate 10 in which the conductor 25 is embedded is obtained. The coil component may be a wound-type coil. In this case, the conductor 25 may be wound around a substrate 10 created by placing a mixed resin composition prepared by kneading a particle group containing first metal magnetic particles 11 and second metal magnetic particles 12 and a binder 13 made of resin or the like in a molding die, and the end faces may be arranged on the surface of the substrate 10.

[0043] Next, the surface of the magnetic substrate 10 where the end faces 25a2 of the lead-out conductor 25a1 of the conductor 25 and the end faces 25b2 of the lead-out conductor 25b1 are exposed is smoothed to remove the natural oxide film (first step). Smoothing the surface of the magnetic substrate 10 is performed, for example, by polishing using an abrasive. As the particle size of this abrasive, it is preferable to use one with a particle size smaller than that of the first metal magnetic particles 11. For example, if the average particle size of the first metal particles 11 is 30 μm, a particle size of 25 μm is selected. Removal of the natural oxide film is performed, for example, by plasma etching using argon gas, sputtering, or the like. The method for removing the natural oxide film is not particularly limited, and any method that can remove the oxide on the surface of the magnetic substrate 10 may be used.

[0044] Next, a first film 23 that contacts one end of the conductor 25 and a second film that contacts the other end of the conductor 25 are formed (second step). In the second step, the first film 23 and the second film are formed using a material having a diffusion rate slower than the diffusion rate of the materials constituting the external electrodes 21 and 22. Hereinafter, a manufacturing method in the case where the first film 23 and the second film are metal oxide films will be described.

[0045] To form a metal oxide film with a thickness T of about 10 nm to 50 nm as the first film 23 and the second film, heat treatment is performed at 120 to 200 °C for 10 to 60 minutes under the atmosphere. Also, after immersing the exposed end faces 25a2 and 25b2 of the conductor 25 in pure water with the pH controlled to 7 to 13 and then drying in the air, a metal oxide film with a thickness T of about 10 nm to 50 nm can be formed. Further, after exposing the exposed end faces 25a2 and 25b2 of the conductor 25 to an atmosphere of 80% RH or more for 10 to 30 minutes and then drying, a metal oxide film with a thickness T of about 10 nm to 50 nm can be formed. To form a metal oxide film with a thickness T of about 50 nm to 100 nm as the first film 23 and the second film, the exposed end faces 25a2 and 25b2 of the conductor 25 are immersed in an aqueous solution with the pH controlled to be alkaline and greater than 13 and then dried in the air. The first film 23 and the second film can also be formed by a vapor deposition method such as a sputtering deposition method, an ion beam deposition method, and a CVD method.

[0046] The first film 23 and the second film can also be formed by applying a resin containing a compound having an effect of forming a passive oxide film on the exposed end faces 25a2 and 25b2 of the conductor 25. Examples of such compounds include carboxylic acids, sulfonic acids, acid anhydrides, alcohols, amines, imidazoles, phosphoniums, silanes, etc. As an example, the first film 23 and the second film can be formed by applying a conductive resin paste containing a metal filler and any of the above compounds to the exposed end faces 25a2 and 25b2 of the conductor 25 and performing heat treatment at 100 °C to 200 °C a plurality of times.

[0047] Finally, external electrodes 21 that contact the first film 23 and external electrodes 22 that contact the second film are formed (third step). Through the above steps, the coil component 1 is manufactured. The manufactured coil component 1 is mounted on a circuit board by soldering the external electrodes 21 and 22 to the land portions of the circuit board, respectively.

[0048] As described above, the coil component 1 includes a first film 23 positioned between one end of the conductor 25 (i.e., the lead-out conductor 25a1) and the external electrode 21, and a second film positioned between the other end of the conductor 25 (i.e., the lead-out conductor 25b1) and the external electrode 22. The diffusion rates in the first film 23 and the second film are slower than the diffusion rates in the external electrodes 21 and 22.

[0049] Generally, in a coil component, thermal expansion and thermal contraction occur due to Joule heat generated when an electric current flows through the coil component and the environmental temperature at which the coil component is used. Such thermal expansion and thermal contraction accumulate strain in the coil component and can cause the coil component to fail. Therefore, in a coil component, particularly the stability of the junction between the conductor and the external electrode is required. For this reason, in a general coil component, it is considered preferable to remove the oxide remaining between the end of the conductor and the external electrode. In contrast, the present invention focuses on the decrease in the bonding strength between the conductor 25 and the external electrodes 21 and 22 due to the alloying of impurity atoms and the material constituting the conductor 25, and positively provides the coil component 1 with the first film 23 and the second film having diffusion rates slower than those of the external electrodes 21 and 22. Thus, by providing the first film 23 and the second film having diffusion rates slower than those of the external electrodes 21 and 22, the movement of impurity atoms is suppressed by the first film 23 or the second film. Therefore, migration of impurity atoms between the conductor 25 and the external electrode 21 and between the conductor 25 and the external electrode 22 can be suppressed. As a result, a decrease in the bonding strength between the conductor 25 and the external electrodes 21 and 22 due to the alloying of impurity atoms and the material constituting the conductor 25 can be suppressed.

[0050] In one embodiment of the present invention, the thickness T of the first film 23 and the thickness of the second film of the coil component 1 are 10 nm or more and 200 nm or less. Thereby, since a Schottky current or a tunnel current can flow through the first film 23 and the second film, the influence on the electrical connection between the conductor 25 and the external electrode 21 by the first film 23 (for example, an increase in the resistance between the conductor 25 and the external electrode 21 due to the first film 23) can be reduced. Similarly, the influence on the electrical connection between the conductor 25 and the external electrode 22 by the second film can be reduced. Therefore, while maintaining the electrical connection between the conductor 25 and the external electrodes 21 and 22, migration of impurity atoms can be suppressed.

[0051] In one embodiment of the present invention, the first film 23 and the second film of the coil component 1 are metal material oxides having an ionization tendency that is the same as or smaller than the ionization tendency of the material constituting the conductor 25. According to this configuration, migration of impurity atoms can be further suppressed by the first film 23 and the second film.

[0052] In the coil component 1 according to one embodiment of the present invention, the unevenness at the interface between the first film 23 and the external electrode 21 and the unevenness at the interface between the second film and the external electrode 22 are larger than the unevenness on the surfaces of the external electrode 21 and the external electrode 22. According to this configuration, the adhesion between the first film 23 and the external electrode 21 and the adhesion between the second film and the external electrode 22 can be improved by the anchor effect.

[0053] The manufacturing method of the coil component 1 according to an embodiment of the present invention includes a second step of forming a first film 23 electrically connected to one end of the conductor 25 (that is, the lead-out conductor 25a1) and a second film electrically connected to the other end of the conductor 25 (that is, the lead-out conductor 25b1). In the second step, the first film and the second film are formed using a material having a diffusion rate slower than the diffusion rate of the material constituting the external electrodes 21 and 22. Thus, since the first film 23 and the second film are formed using a material having a diffusion rate slower than the diffusion rate of the material constituting the external electrodes 21 and 22, the movement of impurity atoms is suppressed by the first film 23 or the second film. Therefore, migration of impurity atoms between the conductor 25 and the external electrode 21 and between the conductor 25 and the external electrode 22 can be suppressed.

[0054] Next, a coil component 100 according to another embodiment of the present invention will be described with reference to FIG. 5. FIG. 8 is a perspective view schematically showing the coil component 100. As shown in the figure, the coil component 100, like the coil component 1, includes a coil conductor 25 in a base body 10, an external electrode 21 provided on the surface of the base body 10, and an external electrode 22 provided at a position spaced apart from the external electrode 21 on the surface of the base body 10. The coil component 100 includes an insulating plate 50 provided in the base body 10, and is different from the coil component 1 in that the conductor 25 is provided on the upper and lower surfaces of the insulating plate 50.

[0055] Similar to the coil component 1, the coil component 100 also includes a first film 23 located between one end of the conductor 25 (that is, the lead-out conductor 25a1) and the external electrode 21, and a second film located between the other end of the conductor 25 (that is, the lead-out conductor 25b1) and the external electrode 22. The diffusion rates in the first film 23 and the second film are slower than the diffusion rates in the external electrodes 21 and 22. Therefore, for the same reason as the coil component 1, migration of impurity atoms between the conductor 25 and the external electrode 21 and between the conductor 25 and the external electrode 22 can be suppressed.

[0056] The dimensions, materials, and arrangements of the respective components described in the various embodiments above are not limited to those explicitly described in each embodiment, and each of these components can be modified to have any dimensions, materials, and arrangements that can be included within the scope of the present invention. Further, components not explicitly described in this specification can be added to each of the above-described embodiments, or some of the components described in each embodiment can be omitted.

[0057] The electronic component according to the present invention is not limited to a coil component, and may be, for example, a capacitor. FIG. 6 is a cross-sectional view schematically showing a capacitor 200 which is an electronic component according to another embodiment of the present invention. As shown in FIG. 6, the capacitor 200 includes a base body 210, a conductor 225 provided inside the base body 210, and external electrodes 202 and 203 provided outside the base body 210. In the embodiment shown in FIG. 6, the capacitor 200 is a so-called MLCC, and the conductor 225 includes a plurality of first electrode layers 221 and a plurality of second electrode layers 222. The first electrode layer 221 and the second electrode layer 222 are alternately arranged with the base material 210 interposed therebetween. The portion of the base material 210 located between the first electrode layer 221 and the second electrode layer 222 functions as a dielectric. Similar to the coil component 1, the capacitor 200 has a first film 23 located between the external electrode 202 and the conductor 225, and another film located between the external electrode 203 and the conductor 225.

[0058] Similar to the coil component 1, the capacitor 200 also includes a first film 23 located between the end of the conductor 225 electrically connected to the external electrode 202 and the external electrode 202, and a second film located between the other end of the conductor 225 electrically connected to the external electrode 203 and the external electrode 203. The diffusion rates in the first film 23 and the second film are slower than the diffusion rates in the external electrodes 202 and 203. Therefore, for the same reason as the coil component 1, migration of impurity atoms between the conductor 225 and the external electrode 202 and between the conductor 225 and the external electrode 203 can be suppressed.

Explanation of Reference Numerals

[0059] 1,100... coil component (electronic component), 10... magnetic substrate, 11... first metal magnetic particle, 12... second metal magnetic particle, 13... binder, 21... external electrode (first external electrode), 22... external electrode (second external electrode), 23... first film, 25... conductor, 25a1... lead-out conductor (one end), 25b1... lead-out conductor (the other end), 200... capacitor (electronic component).

Claims

1. A substrate with a smoothed surface of a molded body containing a plurality of metal magnetic particles, the substrate being defined by a plurality of surfaces, a conductor provided inside or outside the substrate, a first external electrode and a second external electrode electrically connected to the conductor, a first film positioned between an end of the conductor electrically connected to the first external electrode and the first external electrode, a second film positioned between an end of the conductor electrically connected to the second external electrode and the second external electrode, and comprising: the diffusion rates in the first film and the second film are slower than the diffusion rates in the first external electrode and the second external electrode, the first film and the second film are oxides of a metal material having an ionization tendency the same as or smaller than the ionization tendency of the material constituting the conductor, the first film and the second film are formed only on the surface of the plurality of surfaces of the substrate where the ends of the conductor are arranged, an electronic component.

2. The electronic component according to Claim 1, wherein the thickness of the first film and the thickness of the second film are 10 nm or more and 200 nm or less.

3. The electronic component according to Claim 1 or 2, wherein the first film and the second film are amorphous.

4. The electronic component according to any one of Claims 1 to 3, wherein the unevenness at the interface between the first film and the first external electrode and at the interface between the second film and the second external electrode is larger than the unevenness on the surfaces of the first external electrode and the second external electrode.

5. The electronic component according to any one of Claims 1 to 4, wherein the conductor includes a portion wound around the coil axis.

6. A circuit board comprising the electronic component according to any one of Claims 1 to 5.

7. An electronic device comprising the circuit board according to Claim 6.

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