Coil components and their manufacturing methods

Abstract

The present invention provides a coil component and a method for manufacturing the same, wherein the end of a wire is well connected to an external electrode. The coil component comprises: an iron core having a core portion and a flange portion formed on the end face of the core portion; a wire wound around the core portion; and an external electrode formed on the bottom surface of the flange portion, connected to the end of the wire, and having a first metal layer constituting the surface, wherein at least a portion of the aforementioned end of the wire is embedded in the first metal layer.

Description

Technical Field

[0001] This invention relates to coil components and their manufacturing methods. Background Technology

[0002] Conventionally, as a coil component of the winding type, there exists, for example, the component described in Japanese Patent Application Publication No. 2015-50373 (Patent Document 1). This coil component includes: an iron core having a core portion and flange portions formed at both ends of the core portion; a wire wound around the core portion; and an external electrode formed on the bottom surface of the flange portion, to which the end of the wire is connected.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2015-50373

[0004] However, conventional coil components are configured such that the ends of the wire are exposed on the surface of the external electrode. As a result, the wire ends have a relatively low adhesion to the external electrode, and the wire may peel off from the external electrode, reducing the connection between the wire ends and the external electrode. Summary of the Invention

[0005] Therefore, an object of the present invention is to provide a coil component in which the end of a wire is well connected to an external electrode. Another object of the present invention is to provide a method for manufacturing such a coil component.

[0006] To address the aforementioned issues, one embodiment of the present invention provides a coil component comprising: an iron core having a core portion and a flange portion formed on an end face of the core portion; a wire wound around the core portion; and an external electrode formed on the bottom surface of the flange portion, connected to an end of the wire, wherein the external electrode has a first metal layer constituting a surface, and at least a portion of the end of the wire is embedded in the first metal layer.

[0007] According to the above embodiment, at least a portion of the end of the wire is embedded in the first metal layer. Therefore, the contact area between the end of the wire and the external electrode is relatively large, and the end of the wire can be well connected to the external electrode.

[0008] In addition, a method for manufacturing a coil component according to one aspect of the present invention includes the following steps: preparing an iron core having a core portion and a flange portion formed on the end face of the core portion; forming an external electrode on the bottom surface of the flange portion; winding a wire in the core portion; and heating and connecting the end of the wire to the external electrode. When forming the external electrode, a first metal layer is formed by plating to form the surface of the external electrode. Before heating and connecting the wire, a flux containing rosin and an activator is coated on the first metal layer or the end of the wire. When heating and connecting the wire, the first metal layer, the flux, and the end of the wire are overlapped in that order, and the end of the wire is heated, thereby removing the oxide film on the surface of the first metal layer by the flux.

[0009] According to the above embodiment, the activator contained in the flux removes the oxide film on the surface of the first metal layer, thus the first metal layer is easily melted, and at least a portion of the end of the wire is embedded in the first metal layer. Therefore, the contact area between the end of the wire and the external electrode is relatively large, and the end of the wire can be well connected to the external electrode.

[0010] According to the present invention, a coil component can be provided in which the end of a wire is well connected to an external electrode. Furthermore, according to the present invention, a method for manufacturing such a coil component can be provided. Attached Figure Description

[0011] Figure 1 This is a side view showing the coil component of the first embodiment.

[0012] Figure 2 This is a cross-sectional view showing the coil component of the first embodiment.

[0013] Figure 3 This is a cross-sectional view showing the coil component of an embodiment.

[0014] Figure 4A This is a cross-sectional view showing the manufacturing method of the coil component according to the second embodiment.

[0015] Figure 4B This is a side view showing the manufacturing method of the coil component according to the second embodiment.

[0016] Figure 4C This is a cross-sectional view showing the manufacturing method of the coil component according to the second embodiment.

[0017] Figure 4D This is a cross-sectional view showing the manufacturing method of the coil component according to the second embodiment.

[0018] Explanation of reference numerals in the attached figures

[0019] 1…coil component; 10…iron core; 11…first flange portion; 11a…first bottom surface; 12…second flange portion; 12a…second bottom surface; 13…core portion; 13a…first end; 13b…second end; 20…wire; 21…first end; 22…second end; 31…first electrode; 311, 321…first plating layer; 312, 322…second plating layer; 32…second electrode; 40…flux. Detailed Implementation

[0020] The coil component and its manufacturing method according to one aspect of the present invention will now be described in detail with reference to the illustrated embodiments. Furthermore, the drawings contain partially schematic structures and may not always reflect actual dimensions or proportions.

[0021] (First Implementation)

[0022] [structure]

[0023] Figure 1 This is a side view showing the coil component according to the first embodiment of the present invention. Figure 2 This is a cross-sectional view showing the coil component of the first embodiment. Figure 2 yes Figure 1 XX section. Figure 3 This indicates the cross-section of the first end 21 of the wire 20. (Using...) Figures 1-3 The coil components are described.

[0024] The coil component 1 includes: an iron core 10; a wire 20 wound around the iron core 10; and a first electrode 31 and a second electrode 32 serving as external electrodes, which are disposed on the iron core 10 and electrically connected to the wire 20.

[0025] The iron core 10 includes: a core portion 13, which is shaped to extend in a predetermined direction and on which wire 20 is wound; a first flange portion 11, which is formed at a first end 13a in the extending direction of the core portion 13 and extends in a direction orthogonal to the extending direction; and a second flange portion 12, which is formed at a second end 13b in the extending direction of the core portion 13 and extends in a direction orthogonal to the extending direction. The material of the iron core 10 is preferably a sintered ferrite body, a molded body of resin containing magnetic powder, or other magnetic materials, but it can also be a non-magnetic material such as alumina or resin. Furthermore, the bottom surface of the iron core 10 will be used below as the surface on which it is mounted to the mounting substrate.

[0026] The first flange portion 11 has a first bottom surface 11a mounted on the mounting substrate side. The second flange portion 12 has a second bottom surface 12a mounted on the mounting substrate side.

[0027] Wire 20 is wound around core portion 13. A first end 21 of wire 20 is connected to a first electrode 31, and a second end 22 is connected to a second electrode 32. The winding axis (coil axis) of wire 20 is aligned with the extending direction of core portion 13. Wire 20 has a conductive portion 201 and a covering portion 202 covering the conductive portion 201. The conductive portion 201 is, for example, made of copper. The material of the covering portion 202 is preferably, for example, polyurethane resins such as polyamide-imide, imide resins, amide resins, etc., or mixtures thereof. In particular, the covering portion 202, made of a resin with high heat resistance such as polyamide-imide, is less likely to disappear due to heat pressing, and sometimes remains as residue, causing poor pressing, especially when combined with the flux coating based on the manufacturing method described later.

[0028] The first end 21 of the wire 20 is completely embedded within the first electrode 31. This results in a larger contact area between the first end 21 of the wire 20 and the first electrode 31 by at least partially embedding the first end 21 of the wire 20. Therefore, good connectivity between the first electrode 31 and the wire 20 can be ensured. Furthermore, because the first end 21 of the wire 20 is embedded in the first electrode 31, it is less likely to detach from the first electrode 31 during the mounting of the coil component 1 to the mounting substrate. Therefore, good connectivity between the first electrode 31 and the wire 20 can be ensured even after the coil component 1 has been mounted.

[0029] Furthermore, the area exposed on the surface of the first end 21 of the wire 20 is smaller. Here, compared to the surface of the first electrode 31, the exposed portion of the first end 21 of the wire 20 generally has lower solder wettability. Therefore, the exposed area of ​​the first end 21 with lower solder wettability is smaller, resulting in excellent solder wettability of the first electrode 31 of the coil component 1, enabling it to be firmly bonded to the mounting substrate.

[0030] Previously, it was impossible to adequately embed the first end 21 of the wire 20 within the first electrode 31, resulting in the first end 21 of the wire 20 being exposed on the surface of the first electrode 31. The inventors, focusing on the reasons why the first end 21 was not adequately embedded, have found that these reasons are mainly due to the following two points:

[0031] Because a metal oxide film 311a is formed on the surface of the first plating layer 311, the first plating layer 311 does not easily melt even when heated.

[0032] The cover portion 202 of the wire 20 is formed by repelling the molten material (e.g., Sn) constituting the first plating layer 311.

[0033] The inventors further investigated and discovered that, in addition to removing the metal oxide film (typically a high-melting-point metal oxide film) 311a, the flux 40 also has the function of thermally decomposing the resin constituting the cover 202 at a temperature lower than the inherent heat resistance temperature of the resin itself. Based on this technical insight, the function of the flux 40, such as "the flux 40 removes the cover 202," was derived by utilizing the unique function of the flux 40. Thus, the inventors' in-depth research resulted in the conception of the feature of the present invention: "at least partially embedded in the first plating layer 311 of the wire 20."

[0034] The cross-section of wire 20 ( Figure 1 In the cross-section of the wire 20, the shape (cross-sectional shape) of the conductive portion 201 at the first end 21 of the wire 20 is the same as the shape of the conductive portion 201 located at the core portion 13 of the wire 20. Here, "cross-section" in this specification refers to a cross-section orthogonal to the extension direction of the wire 20. Specifically, the cross-sectional shape of the conductive portion 201 at the first end 21 of the wire 20 is approximately circular. In conventional crimping processes, the wire is usually flattened by applying a large pressing force. As a result, the cross-sectional shape of the conductive portion at the end of the wire is, for example, a flat shape, and the original shape is not retained. In contrast, in this embodiment, for example as described in the manufacturing method described later, the first end 21 of the wire 20 can be connected to the first electrode 31 without a large pressing force during the crimping process. That is, the cross-sectional shape of the conductive portion 201 at the end 21 of the wire 20 retains the original shape, thus causing less damage to the coil component 1, reducing the risk of wire breakage, and suppressing the formation of cracks on the core 10 and the first electrode 31.

[0035] In the first end 21 of the wire 20, on the side of the bottom surface 11a of the first flange portion 11, the conductive portion 201 is exposed from the cover portion 202. More specifically, the area of ​​the conductive portion 201 exposed at the first end 21 of the wire 20 is larger on the side of the bottom surface 11a of the first flange portion 11 compared to the surface side of the external electrode (first electrode 31). Figure 2 (Not shown in the figure). Typically, the cover 202 is made of an insulating material, while the first electrode 31 and the conductive part 201 are made of metal. Moreover, metals have a higher degree of interconnectivity than insulating materials. Therefore, when the conductive part 201 is exposed from the cover 202 at the first end 21 of the wire 20, the conductive part 201 is connected to the first electrode 31 at the first end 21 of the wire 20, resulting in excellent connectivity. This improves the fit during installation of the coil component 1.

[0036] Regarding the area of ​​the conductive portion 201 exposed at the first end 21 of the wire 20, the area on the bottom surface 11a side of the first flange portion 11 is larger than the area on the surface side of the first electrode 31. This is because, as explained below, the covering portion 202 on the bottom surface 11a side is easily removed. In the crimping process of the manufacturing method described later, the covering portion 202 of the first end 21 of the wire 20, which exists before the crimping process, and the first plating layer 311 are crimped together while in contact with the flux. More specifically, in the heat connection of the wire 20, the first plating layer 311, the flux 40, and the first end 21 of the wire 20 are overlapped in that order, and the first end 21 of the wire 20 is heated. Here, if the flux 40 is heated, the covering portion 202 is decomposed. Therefore, at the first end 21 of the wire 20, the portion of the covering portion 202 near the bottom surface 11a side of the first flange portion 11 is preferentially decomposed compared to the surface side of the first electrode 31. Therefore, compared with hot pressing without using flux 40, the cover 202 of the first end 21 can be removed at low temperature (e.g., 200°C to 300°C) and low pressure or without pressure, and the first end 21 of the wire 20 can be embedded in the first electrode 31.

[0037] In contrast, in conventional hot-pressing without flux 40, the covering portion 202 of the first end 21 of the wire 20 is heated from the surface side of the first electrode 31. Therefore, the covering portion 202 near the surface side of the first electrode 31 is preferentially disassembled. Regarding the exposed area of ​​the conductive portion 201, the bottom surface 11a side of the first flange portion 11 is sometimes smaller than the surface side of the first electrode 31.

[0038] Furthermore, as described above, the flux 40 decomposes the cover portion 202, so even wires 20 with a cover portion 202 made of a material with high heat resistance (more specifically, polyamide-imide, etc.) can have their cover portion 202 removed, exposing the conductive portion 201. In contrast, in conventional hot-pressing without the use of flux 40, the heat-resistant cover portion 202 cannot be sufficiently removed, requiring further processes such as laser irradiation.

[0039] Furthermore, at the first end 21 of the wire 20, as described above, at least in the portion near the bottom surface 11a of the first flange 11, the conductive portion 201 is exposed from the cover portion 202. From the viewpoint of further improving the engagement during installation of the coil component 1, it is preferable that the first end 21 of the wire 20 does not have the cover portion 202. This is because, without the cover portion 202, the exposed area of ​​the conductive portion 201 at the first end 21 is further increased, and the contact area with the first electrode 31 is increased.

[0040] The following can be confirmed by the following method: at the first end 21 of the wire 20, on the side of the bottom surface 11a of the first flange 11, the conductive portion 201 is exposed from the cover portion 202; and regarding the area of ​​the conductive portion 201 exposed at the first end 21 of the wire 20, the area on the bottom surface 11a side of the first flange 11 is larger than the area on the surface side of the first electrode 31. Figure 1 As shown, the coil component 1 is cut off at the center of the first electrode 31, forming a cross-section (XX cross-section). Using a scanning electron microscope (SEM) and energy dispersive X-ray diffraction (EDX), the signal from the material constituting the cover portion 202 is measured for the formed cross-section. Based on the measurement results, the cross-sectional image is mapped to produce an analytical image representing the distribution of the aforementioned material. The vicinity of the wire 20 (more specifically, the vicinity of the surface of the conductive portion 201) is observed in the analytical image. During observation, based on the mapping position and amount of carbon (C), it can be confirmed that the cover portion 202 does not exist at the first end 21.

[0041] A first electrode 31 is disposed on the first bottom surface 11a of the first flange portion 11. The first electrode 31 has: a base electrode layer 313 formed on the first bottom surface 11a of the first flange portion 11, a second plating layer 312 formed on the base electrode layer 313, and a first plating layer 311 formed on the second plating layer 312. The first plating layer 311 constitutes the surface of the first electrode 31. The first plating layer 311 includes a metal oxide film 311a. A metal oxide film 311a is disposed on the surface of the first plating layer 311. The metal oxide film 311a may exist in a partial area of ​​the surface of the first plating layer 311 or may exist on the entire surface. The metal oxide film 311a is a film obtained by partially oxidizing the surface of the first plating layer 311. More specifically, the metal oxide film 311a has an oxide film formed after the formation of the first plating layer 311 in the external electrode formation step described later, and an oxide film on the surface portion of the first plating layer 311 that is re-formed when the first end 21 of the wire 20 and the first electrode 31 are connected in the connection step. That is, the latter oxide film is formed by re-oxidizing the surface portion of the newly formed first plating layer 311 after the connection is performed (after the wire 20 is embedded), which is an oxide film temporarily reduced by the flux 40 (activator) during the heat connection (a part of the former oxide film).

[0042] The first plating layer 311 is, for example, a metal layer formed by plating. The first plating layer 311 contains, for example, tin, and more specifically, a Sn (tin) layer and a tin alloy layer with excellent solder wettability. The metal oxide film 311a is a film formed by the oxidation of the surface of the first plating layer 311 by oxygen in the atmosphere. The material of the metal oxide film 311a is, for example, tin oxide.

[0043] When the coil component 1 is manufactured using the manufacturing method described later, the first plating layer 311 contains, for example, carbon. The presence of carbon within the first plating layer 311 can be confirmed by the following methods. Figure 1 As shown, the coil component 1 is cut off at the center of the first electrode 31 to form a cross-section (XX section). Signals from carbon elements are measured in the formed cross-section using SEM and EDX. Based on the measurement results, the cross-sectional image is mapped to produce an analytical image representing the distribution of carbon elements. The first plating layer 311 of the analytical image is observed. Thus, the presence of carbon elements within the first plating layer 311 can be confirmed.

[0044] In addition, Fourier transform infrared spectroscopy (FT-IR) can be used at this time to confirm that the carbon element is part of the resin or that the resin is a residue from flux 40 (more specifically, the resin contains rosin or its modifiers).

[0045] The second plating layer 312 is a metal layer formed by plating. The second plating layer 312 is, for example, a Ni layer (barrier layer) made of Ni that is resistant to solder erosion.

[0046] The second plating layer 312 does not contact the first end 21 of the wire 20.

[0047] The base electrode layer 313 is, for example, a sintered body obtained by sintering a conductive paste such as Ag glass paste coated by an impregnation method. When the base electrode layer 313 is a sintered body, the strength and impact resistance of the base electrode layer 313 itself can be ensured, as well as the fixing force between the base electrode layer 313 and the first flange portion 11 can be ensured. The base electrode layer 313 is, for example, an Ag layer with excellent low resistance.

[0048] [Example]

[0049] exist Figure 3 The figure shows a cross-section of the coil component 1 in the embodiment. Figure 3 Equivalent to Figure 2 Enlarged cross-sectional view of the first end 21 of the wire 20 (note that...) Figure 3 Compared to Figure 2 (The top and bottom are opposite). The first electrode 31 has: a base electrode layer 313 containing Ag formed on the first flange portion 11, a second plating layer 312 made of Ni formed on the base electrode layer 313, and a first plating layer 311 made of Sn formed on the second plating layer 312. A metal oxide film 311a exists on the surface of the first plating layer 311. The wire 20 has: a conductive portion 201 made of Cu, and a covering portion 202 made of polyurethane covering the conductive portion 201.

[0050] The first end 21 of the wire 20 is partially embedded in the first electrode 31 (specifically, the first plating layer 311) and does not contact the second plating layer 312. The cross-sectional shape of the conductive portion 201 at the first end 21 of the wire 20 is approximately circular, the same as the cross-sectional shape of the conductive portion 201 located at the core portion 13 of the wire 20. EDX confirms that the first end 21 of the wire 20 does not have a covering portion 202, but consists only of the conductive portion 201. Furthermore, EDX confirms that carbon is present in the first plating layer 311. This carbon is presumably residue from the flux 40 used in its manufacture. The flux 40 used in the manufacture of the coil component 1 contains rosin, solvent, and activator. In the above embodiment, the first end 21 of the wire 20 is partially embedded in the first electrode 31, but in several other embodiments, the first end 21 of the wire 20 is completely embedded in the first electrode 31.

[0051] [Manufacturing method for coil components]

[0052] Reference Figures 4A to 4D An example of the manufacturing method of coil component 1 will be described. Figures 4A to 4D These are side views and sectional views used to illustrate the manufacturing method of coil component 1. Figure 4C express Figure 4B The YY section.

[0053] The manufacturing method of coil component 1 includes a core preparation step, an external electrode formation step, a flux coating step, a wire winding step, and a connection step.

[0054] More specifically, the manufacturing method of the coil component includes the following steps:

[0055] Prepare an iron core 10, which has a core portion 13 and first and second flange portions 11 and 12 formed on the end face of the core portion 13 (iron core preparation step);

[0056] External electrodes (first and second electrodes 31 and 32) are formed on the bottom surfaces 11a and 12a of the first and second flange portions 11 and 12 (external electrode forming step);

[0057] Wire 20 is wound onto core section 13 (wire winding step); and

[0058] The ends 21 and 22 of the wire are heated and connected to the first and second electrodes 31 and 32 (connection step).

[0059] When forming the first and second electrodes 31 and 32, a first metal layer (first plating layer 311, 321) is formed by plating to constitute the surface of the first and second electrodes 31 and 32.

[0060] Before heating the connecting wire 20, a flux 40 containing rosin and an activator is applied to the first plating layers 311, 321 or the ends 21, 22 of the wire 20 (flux coating step).

[0061] When heating the connecting wire 20, the first plating layers 311, 321, flux, and the ends 21, 22 of the wire 20 are overlapped in that order, and the ends 21, 22 of the wire 20 are heated, thereby the flux 40 removes the metal oxide film 311a on the surface of the first plating layers 311, 321.

[0062] In the core preparation step, a core 10 is prepared. For example, the core 10 is integrally formed using a metal mold. Thus, a core 10 is prepared having a core portion 13, a first flange portion 11 formed at a first end 13a of the core portion 13, and a second flange portion 12 formed at a second end 13b of the core portion 13.

[0063] In the external electrode formation step, first and second electrodes 31 and 32 are formed on the bottom surfaces 11a and 12a of the first and second flange portions 11 and 12. During the formation of the first and second electrodes 31 and 32, first plating layers 311 and 321 are formed by plating to constitute the surfaces of the first and second electrodes 31 and 32. More specifically, in the external electrode formation step, a base electrode layer 313, a second plating layer 312, and a first plating layer 311 are sequentially formed on the first bottom surface 11a of the first flange portion 11. The base electrode layer 313 is formed, for example, by applying conductive paste to the bottom surface 11a of the first flange portion 11 using an impregnation method and then firing the coating film. The conductive paste, for example, contains glass and conductive powder. The conductive powder is, for example, Ag powder. Next, the second plating layer 312 is formed, for example, by plating Ni. Furthermore, the first plating layer 311 is formed, for example, by plating Sn. The metal oxide film 311a is formed, for example, by reacting the surface portion of the first plating layer 311 with oxygen in the atmosphere after Sn plating. Furthermore, in the finally manufactured coil component 1, in addition to the oxide film formed after Sn plating, a metal oxide film 311a is also formed after the heat connection described later. This latter metal oxide film 311a is formed by oxidizing the surface portion of the first plating layer 311, which is formed again during the connection step, for example, when connecting the first end 21 of the wire 20 and the first electrode 31. (The text then refers to the state after heat connection.) Figure 4C In the process, no metal oxide film 311a is formed on the surface portion of the first plating layer 311 that has been re-formed.

[0064] In the flux coating step, before heating the connecting wire 20, such as Figure 4AAs shown, a flux 40 containing rosin and an activator is coated on the first plating layer 311 (metal oxide film 311a). Specifically, the iron core 10 is immersed in the flux 40 placed in the container 100 so that the first electrode 31 disposed on the first bottom surface 11a of the iron core 10 is coated with the flux 40.

[0065] In the wire winding step, wire 20 is wound onto the core portion 13.

[0066] In the connection step, the ends 21 and 22 of the wire 20 are heated and connected to the first and second electrodes 31 and 32. More specifically, in the connection step, when heating and connecting the wire 20, the first plating layer 311, the flux 40, and the ends 21 of the wire 20 are overlapped, and the ends 21 of the wire 20 are heated, thereby removing the metal oxide film 311a on the surface of the first plating layer 311 by the flux 40.

[0067] In detail, in the connection steps, firstly, as... Figure 4B and Figure 4C As shown, the first end 21 of the wire 20 is disposed on the surface of the first plating layer 311, such that the flux 40 is sandwiched between the surface of the first plating layer 311 and the first end 21 of the wire 20. Specifically, the first end 21 of the wire 20 is bent so that it comes into contact with the coating film of the flux 40 formed on the first plating layer 311. Thus, the first plating layer 311 and the first end 21 of the wire 20 come into contact with the flux 40.

[0068] Furthermore, in this specification, contacting the first plating layer 311 and the first end 21 of the wire 20 with the flux 40 also includes contacting the metal oxide film 311a and the first end 21 of the wire 20 with the flux 40.

[0069] In the connection step, the next step is as follows: Figure 4C and Figure 4D As shown, a heated wire 20 is at least partially embedded in a first electrode 31, connecting the first end 21 of the wire 20 to the first electrode 31. The heating unit is, for example, a heater (more specifically, a heater configured to operate at low pressure compared to conventional methods, or a heater configured to not apply pressure) and a soldering iron 300. Specifically, for example, the soldering iron 300, which serves as the heating unit, is brought into contact with the first end 21 of the wire 20, thereby heating the first end 21 of the wire 20. Through this heating, the flux 40 removes the metal oxide film 311a and decomposes the covering portion 202 of the first end 21 of the wire 20. Thus, the covering portion 202 of the first end 21 of the wire 20 is removed, and the metal oxide film 311a is removed, embedding the first end 21 of the wire 20 (the conductive portion 201 in the first end 21) in the first electrode 31.

[0070] In this crimping process, the flux 40, when heated (more specifically, in addition to removing the metal oxide film 311a, also decomposes and removes the covering portion 202 of the first end 21), allows the wire 20 and the first electrode to be connected (i.e., a low-pressure connection is possible) even with reduced pressing force when pressing the first end 21 of the wire 20 against the first plating layer 311, compared to conventional crimping processes that do not use flux 40. Thus, the first end 21 of the wire 20 can be connected to the first electrode 31 without applying unnecessary pressing force to the core 10, the wire 20, and the first electrode 31. Therefore, in the crimping process, damage to the coil component 1 can be reduced, the risk of wire breakage can be reduced, and the generation of cracks on the core 10 and the first electrode 31 can be suppressed.

[0071] Furthermore, it is preferable that the crimping process can be performed without applying pressure (i.e., a pressure-free connection can be made). In the case of performing the crimping process without applying pressure, for example, if the bottom surface of the iron core 10 is positioned on the upper side, the first end 21 of the wire 20 will enter the first plating layer 311 by the weight of the wire 20 itself.

[0072] Furthermore, during the crimping process, a low-pressure connection can be performed, so the first end 21 of the wire 20 does not deform and retains its original shape. That is, the cross-sectional shape of the conductive portion 201 in the end 21 of the crimped wire is the same as the cross-sectional shape of the conductive portion 201 located in the core portion 13 of the wire 20 in the cross-section of the wire 20, specifically, it is approximately circular.

[0073] Furthermore, during the crimping process, a low-pressure connection can be achieved, thus at least partially embedding the end 21 of the wire 20 in the first electrode 31, preventing contact with the second plating layer 312. The fact that the end 21 of the wire 20 does not contact the second plating layer 312 means that during the crimping process, no excessive pressure is applied, preventing cracks from forming in the second plating layer 312 due to pressure. This suppression of crack formation, for example, means suppressing the reduction of the solder erosion resistance of the first electrode 31 when the second plating layer 312 is a solder erosion resistant barrier layer. Conversely, if cracks form in the second plating layer during the crimping process, solder can reach the base electrode layer through the cracks during the installation of the coil component 1, sometimes failing to adequately suppress solder erosion. The fact that the end 21 of the wire 20 does not contact the second plating layer 312 also means that during the crimping process, no excessive pressure is applied to the core 10. This reduces the pressure on the core 10, thus reducing damage to the core 10 (more specifically, the formation of cracks). Furthermore, during the crimping process, low-pressure or no-pressure connections can be made, so no large pressing force is applied during the crimping process, which can suppress the risk of wire breakage.

[0074] Furthermore, compared to conventional crimping processes, this crimping process can reduce the temperature of the heating wire 20 (heating temperature) (i.e., low-temperature connection is possible). Therefore, the first end 21 of the wire 20 can be connected to the first electrode 31 without applying unnecessary heat to the core 10, the wire 20, and the first electrode 31. The heating temperature is, for example, 200°C to 300°C. Thus, thermal damage to the core 10, the wire 20, and the electrodes 31 and 32 can be reduced during the crimping process.

[0075] Furthermore, since no unnecessary heat is applied during the crimping process, it is less likely to form a metal oxide film 311a with low solder wettability. Also, during the crimping process, even if the conductive portion 201 is exposed from the first plating layer 311, it is less likely to form an oxide film with low solder wettability on the surface of the exposed conductive portion 201. Therefore, a stable bond can be formed when the coil component 1 is mounted on the mounting substrate.

[0076] Furthermore, in conventional crimping processes, the cover portion is heated to a temperature above the heat resistance temperature of the resin constituting the cover portion (e.g., polyurethane, polyamide, and polyamide-imide), and removed from the end of the wire by thermal decomposition or the like. For example, with respect to a cover portion made of polyamide-imide, instead of removing the cover portion by conventional hot crimping, it is removed by irradiating the cover portion with a laser.

[0077] In this way, compared with the past, low-temperature connection and low-pressure connection can be achieved through crimping, so the cover 202 and residues of the material constituting the cover 202 can be easily removed from the first electrode 31 from the first end 21 of the wire 20. In this way, the cover 202 with low solder wettability and the residue can be easily removed from the first electrode 31, so the coil component 1 can be firmly bonded to the mounting substrate during installation.

[0078] As described above, low-pressure and low-temperature bonding can be performed during the crimping process. This is because heating bonding is performed while the first plating layer 311 is in contact with the flux 40. Specifically, by heating the flux 40, the metal oxide film 311a on the surface of the first plating layer 311 (e.g., the Sn layer) can be easily removed by the activator contained in the flux 40. As a result, the first plating layer 311 melts easily, and consequently, the first end 21 of the wire 20 is easily embedded.

[0079] Flux 40 contains rosin and an activator. The rosin may be, for example, natural rosin and modified rosin. Modified rosin may include, for example, rosin obtained by reducing natural rosin (reduced rosin), polymerized rosin (polymerized rosin), and disproportionated rosin (disproportionated rosin); as well as rosin derivatives obtained by introducing substitution groups, etc., into natural rosin. The rosin may contain only one type of rosin, or may contain two or more types in combination.

[0080] The activator functions as a reducing agent. When the flux 40 contains an activator, during the crimping process, the flux 40 promotes the reduction reaction of the metal oxide film 311a. Thus, the activator promotes the removal of the metal oxide film 311a, thereby facilitating the embedding of at least a portion of the end 21 of the wire 20 into the plating layer 311. The activator can be, for example, an organic acid such as a carboxylic acid, a haloalcohol, a halohydrocarbon, or an amine. Carboxylic acids can be, for example, monocarboxylic acids such as formic acid, acetic acid, lauric acid, and palmitic acid; and dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, octanoic acid, azelaic acid, sebacic acid, and phthalic acid. The activator may be one of these alone or in combination with two or more.

[0081] Flux 40 may also contain a solvent. The solvent can adjust the viscosity of flux 40. Examples of solvents include alcohols, ketones, esters, ethers, aromatic hydrocarbons, and aliphatic hydrocarbons. Alcohols include, for example, polyols such as ethylene glycol. The solvent may be one of these solvents alone, or two or more may be combined.

[0082] In the crimping process, flux 40 is used, so in the coil component 1, carbon elements (more specifically, carbon elements from the structural composition of flux 40) are present in the first plating layer 311 (more specifically, within and on the surface of the first plating layer 311).

[0083] Additionally, in coil component 1, residues of flux 40 used during manufacturing are sometimes present in the first plating layer 311. When flux 40 containing rosin, solvent, and activator is used in the manufacturing method of coil component 1, the residues of flux 40 may be, for example, rosin or a modified rosin.

[0084] In the above description, the case in which the first end 21 of the wire 20 is connected to the first electrode 31 has been explained, but the second end 22 of the wire 20 can be connected to the second electrode 32 in the same way.

[0085] (Second Implementation)

[0086] The second embodiment differs from the first embodiment in that flux 40 is applied to the first end 21 of the wire 20 instead of the surface of the first plating layer 311. Specifically, in the first embodiment, the flux application step is performed before the wire winding step, but in the second embodiment, the flux application step is performed after the wire winding step. This different structure will be described below. Furthermore, in the second embodiment, the same reference numerals as in the first embodiment are used for the same structures as in the first embodiment, and therefore their description is omitted.

[0087] The manufacturing method of the coil component 1 according to the second embodiment includes a core preparation step, an external electrode formation step, a wire winding step, a flux coating step, a contact step, and a connection step.

[0088] In the wire winding step, after the wire 20 with the core portion 13 wound, the first end 21 of the wire is not bent and does not come into contact with the first electrode 31.

[0089] In the flux coating step, flux 40 is applied to the first end 21 of the wire 20. For example, the first end 21 of the wire 20 is immersed in... Figure 4A The flux 40 is contained in the container 100 shown, and the flux 40 is applied to the first end 21 of the wire 20.

[0090] In the contact step, the first end 21 of the wire 20 is bent so that the first end 21 of the wire 20 and the first plating layer 311 come into contact with the flux 40. Thus, the flux 40 can be sandwiched between the surface of the first plating layer 311 and the first end 21 of the wire 20, and the surface of the first plating layer 311 comes into contact with the first end 21 of the wire 20.

[0091] In the above embodiment, the ends 21 and 22 of the wire 20 are completely embedded in the electrodes 31 and 32, but this is not a limitation. It is sufficient that at least a portion of the ends 21 and 22 of the wire 20 are embedded in the electrodes 31 and 32.

[0092] In the above embodiment, the cross-section of the wire 20 ( Figure 1 In the cross-section of the wire 20, the shape of the conductive portion 201 at the first end 21 is the same as the shape of the conductive portion 201 located in the core portion 13, but is not limited thereto. The cross-sectional shape of the conductive portion 201 at the first end 21 may also be different from the cross-sectional shape of the conductive portion 201 in the core portion 13. Furthermore, when the cross-sectional shapes of the conductive portions 201 are the same, they do not need to be exactly the same, and can be substantially the same.

[0093] In the above embodiment, the structure of the first electrode 31 has been described, but it is not limited thereto. In the coil component 1, the second electrode 32 may also have the same structure as the first electrode 31. That is, the second electrode 32 may also have a first plating layer 321, a second plating layer 322, and a base electrode layer 323. Thus, by having the same structure as the first electrode 31, the second end 22 of the wire 20 is well connected to the second electrode 32, thereby further improving the connectivity between the wire 20 and the electrodes 31 and 32. However, it is not limited to the above structure; any one of the first and second electrodes 31 and 32 may have the above structure. Furthermore, if the coil component 1 also has a third electrode and a fourth electrode as described above, any one of the first to fourth electrodes may also have the above structure.

[0094] In the above embodiments, electrodes 31 and 32 have plating layers formed by plating, but are not limited thereto. Electrodes 31 and 32 may also have metal layers formed by methods other than plating. That is, electrodes 31 and 32 have: base electrode layers 313 and 323 formed on the bottom surfaces 11a and 12a of the flange portions 11 and 12, and metal layers formed on the base electrode layers 313 and 323. The metal layers are, for example, plating layers and metal layers formed by methods other than plating. In the case where the metal layer is a plating layer, in the first embodiment, the first plating layer corresponds to the first metal layer, and the second plating layer corresponds to the second metal layer.

[0095] In the above embodiment, the first electrode 31 has two plating layers 311 and 312, and the second electrode 32 has two plating layers 321 and 322, but is not limited thereto. For example, the electrodes 31 and 32 may also have more than three plating layers.

[0096] The second plating layers 312 and 322 do not contact the first ends 21 and 22 of the wire 20, but are not limited thereto. For example, the second plating layers 312 and 322 may also contact the first ends 21 and 22 of the wire 20.

[0097] In the above embodiment, the wire 20 is a single strand, but it is not limited to this. When there are two wires 20, the coil component 1 can employ a common-mode choke. Specifically, when there are two wires 20, the first flange portion 11 has two legs on the first bottom surface 11a side, with a first electrode disposed on one leg and a third electrode disposed on the other leg. The second flange portion 12 has two legs on the second bottom surface 12a side, with a second electrode disposed on one leg and a fourth electrode disposed on the other leg. The first end of one wire (the first wire) is connected to the first electrode, and the second end is connected to the second electrode. The first end of the other wire (the second wire) is connected to the third electrode, and the second end is connected to the fourth electrode.

[0098] In the above embodiments, electrodes 31 and 32 have base electrode layers 313 and 323, but are not limited thereto. Electrodes 31 and 32 may, for example, replace at least one of the base electrode layers 313 and 323, and have metal terminals made of Cu.

[0099] In the above embodiment, flux 40 is applied to either the surface of the first plating layer 311 or the first end 21 of the wire 20, but is not limited thereto. Alternatively, flux 40 may be made to contact both the surface of the first plating layer 311 and the first end 21 of the wire 20 while the surface of the first plating layer 311 and the first end 21 of the wire 20 are in contact.

[0100] This invention is not limited to the first and second embodiments, and can be implemented in various ways as long as the spirit of the invention is not changed. Furthermore, the structures shown in the first and second embodiments are examples and are not particularly limited; various modifications can be made without substantially departing from the effects of the invention. For example, the items described in the first and second embodiments can be appropriately combined.

Claims

1. A coil component comprising: An iron core having a wound core portion and a flange portion formed on the end face of the wound core portion; Wire, wound around the core portion; and An external electrode, formed on the bottom surface of the flange, is connected to the end of the wire and has a first metal layer constituting the surface. The first metal layer constituting the surface is a first plating layer containing Sn. At least a portion of the end of the wire is completely embedded within the first plating layer containing Sn, which is the first metal layer. The cross-sectional shape of the end of the wire remains unchanged. The wire has a conductive portion and a covering portion that covers the conductive portion. The cover portion comprises polyurethane or polyamide. Carbon is present inside the first metal layer, and the carbon is part of the resin. The resin contains rosin or its modifiers. By overlapping the first metal layer, the flux, and the ends of the wire in that order, and by heating the wire and the external electrode together, the oxide film on the surface of the first metal layer is removed by the flux, thereby at least partially embedding the ends of the wire completely within the first metal layer.

2. The coil component according to claim 1, wherein, In the cross-section of the wire, the shape of the conductive portion at the end of the wire is the same as the shape of the conductive portion located at the core portion of the wire.

3. The coil component according to claim 1, wherein, At the end of the wire, on the bottom side of the flange, the conductive portion is exposed from the cover.

4. The coil component according to claim 3, wherein, At the end of the wire, the area of ​​the exposed conductive portion is larger on the bottom side of the flange than on the surface side of the external electrode.

5. The coil component according to claim 1 or 2, wherein, The external electrode also has a second metal layer covered by the first metal layer. At least a portion of the end of the wire is embedded in the first metal layer and does not contact the second metal layer.

6. The coil component according to claim 1 or 2, wherein, The external electrode also has a second metal layer covered by the first metal layer. The second metal layer is a barrier layer that is resistant to solder corrosion.

7. A method for manufacturing a coil component, comprising the following steps: Prepare an iron core having a wound core portion and a flange portion formed on the end face of the wound core portion; An external electrode is formed on the bottom surface of the flange portion; Wire is wound on the core portion; and The end of the wire is heated and connected to the external electrode. When forming the external electrode, a first metal layer is formed by plating to constitute the surface of the external electrode. The first metal layer is a first plating layer containing Sn. Before heating and connecting the wires, a flux containing rosin and an activator is applied to the first metal layer or the end of the wires. When heating and connecting the wires, the first metal layer, the flux, and the ends of the wires are overlapped, and the ends of the wires are heated, thereby removing the oxide film on the surface of the first metal layer by the flux. At least a portion of the end of the wire is completely embedded within the first plating layer containing Sn, which is the first metal layer. The cross-sectional shape of the end of the wire remains unchanged.

8. The method for manufacturing the coil component according to claim 7, wherein, When heating and connecting the wire, the end of the wire was not pressed against the first metal layer.

9. The method for manufacturing a coil component according to claim 7 or 8, wherein, The wire uses a structure having a conductive portion and a covering portion that covers the conductive portion. When the wire is heated and connected, at the end of the wire, on the bottom side of the flange, the flux decomposes the covering portion.

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