Coil Device

Abstract

To provide a coil device which is easy to manufacture and can ensure high quality.SOLUTION: A coil device 10 includes a coil 30, a core 20 to which a coil 30 is attached, and an electrode 40 formed on a surface of the core 20 and to which a lead portion 30a of the coil 30 is connected. The electrode 40 has a first region 41 and a second region 42. The first region 41 sequentially includes an underlying electrode layer 40a, a conductive paste layer 40b, and a plating layer 40c, and the second region 42 sequentially includes an underlying electrode layer 40a and a plating layer 40c. The lead portion 30a is arranged in the plating layer 40c in the second region 42.SELECTED DRAWING: Figure 2A

Description

[Technical Field]

[0001] The present invention relates to a coil device. [Background technology]

[0002] Conventionally, a technique for applying a conductive paste such as resin Ag to the electrode structure of a coil device has been known. For example, the invention described in Patent Document 1 employs the following electrode structure: a first electrode layer is formed on the surface of the flange, a coil lead-out portion is connected to the surface of the first electrode layer, a second electrode layer is formed on the surface of the first electrode layer so as to cover the lead-out portion, and a plating layer is formed on the surface of the second electrode layer. Both the first electrode layer and the second electrode layer are formed from conductive paste.

[0003] The conductive paste functions as a buffer layer that alleviates the difference in thermal stress between the solder and the plating layer when the coil device is mounted on a mounting substrate, for example, by soldering. Therefore, by using the conductive paste as the electrode material for the first and second electrode layers, it is expected that the occurrence of solder cracks due to the difference in thermal stress between the solder and the plating layer will be prevented.

[0004] Furthermore, the plating layer has relatively high solder wettability, so by providing a plating layer on the outermost layer of the electrode, it is expected that when the coil device is mounted on a mounting board, for example by soldering, the connection reliability between the coil device and the mounting board can be sufficiently ensured.

[0005] In the invention described in Patent Document 1, the plating layer is formed after the coil is attached to the core. Therefore, when the plating layer is formed, there is a risk that plating liquid will penetrate into the coil, which may affect the quality of the coil device. Therefore, in the invention described in Patent Document 1, a resin coating layer that covers the coil is provided on the core (winding core portion) to protect the coil from the penetration of plating liquid.

[0006] However, the invention described in Patent Document 1 requires a step of covering the coil with a resin coating layer, which may complicate the manufacturing process and make quality control difficult. Furthermore, even if the coil is covered with a resin coating layer, there is no guarantee that the problem of the plating solution penetrating into the coil can be completely avoided. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-286807 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a coil device that is easy to manufacture and can ensure high quality. [Means for solving the problem]

[0009] In order to achieve the above object, a coil device according to a first aspect of the present invention comprises: A coil and a core to which the coil is attached; an electrode formed on a surface of the core and connected to a lead-out portion of the coil; The electrode includes, in order, a base electrode layer, a conductive paste layer, and a plating layer; The lead portion is disposed on the plating layer.

[0010] In the coil device according to the first aspect of the present invention, the electrodes contain a conductive paste layer. Therefore, when the coil device is mounted on a mounting board, for example by soldering, the conductive paste layer functions as a buffer layer, thereby preventing solder cracks caused by differences in thermal stress between the solder and the plating layer. Furthermore, because the electrodes contain a plating layer, the relatively high solder wettability of the plating layer ensures sufficient connection reliability between the coil device and the mounting board.

[0011] In particular, in the coil device according to the first aspect of the present invention, the electrode includes, in order, a base electrode layer, a conductive paste layer, and a plating layer, and the lead portion is disposed on the plating layer. This electrode structure can be obtained, for example, by forming a laminated electrode including a base electrode layer, a conductive paste layer, and a plating layer, and then attaching the coil to the core and connecting the lead portion to the electrode (plating layer). In this case, since the coil is not attached to the core during the formation of the plating layer, there is no risk of plating liquid permeating into the coil, and deterioration of the quality of the coil device due to the permeation of plating liquid can be prevented. Furthermore, since there is no risk of plating liquid permeating into the coil, there is no need to provide the coil device with a means for protecting the coil from the permeation of plating liquid (for example, the resin coating layer described in Patent Document 1), which simplifies the manufacturing process of the coil device.

[0012] In order to achieve the above object, a coil device according to a second aspect of the present invention comprises: A coil and a core to which the coil is attached; an electrode formed on a surface of the core and connected to a lead-out portion of the coil; the electrode has a first region and a second region; the first region includes, in order, a base electrode layer, a conductive paste layer, and a plating layer; the second region includes, in order, the base electrode layer and the plating layer; The lead portion is disposed on the plating layer in the second region.

[0013] In a coil device according to a second aspect of the present invention, the electrode has a first region and a second region. The first region includes, in order, a base electrode layer, a conductive paste layer, and a plating layer. Therefore, when the coil device is mounted on a mounting board via the first region, for example, by soldering, it is possible to prevent solder cracks and improve the connection reliability between the coil device and the mounting board for the same reasons as in the coil device according to the first aspect of the present invention.

[0014] The second region includes, in order, a base electrode layer and a plating layer, and the lead portion is disposed on the plating layer in the second region. Such an electrode structure can be obtained, for example, by forming a laminated electrode including the base electrode layer and the plating layer, and then attaching the coil to the core and connecting the lead portion to the electrode (plating layer). Therefore, for the same reasons as the coil device according to the first aspect of the present invention, the coil device according to the second aspect of the present invention can also prevent quality degradation of the coil device and simplify the manufacturing process of the coil device.

[0015] In particular, when only the first region of the first and second regions is provided with a conductive paste layer (i.e., when the second region is not provided with a conductive paste layer), the second region is less likely to deform than the first region, and the lead portion is less likely to peel off from the second region. Therefore, when the lead portion is bonded to the second region, for example, by thermocompression, deformation of the second region or peeling of the lead portion from the electrode can be prevented, and deterioration of the quality of the coil device due to deformation of the electrode (second region) or peeling of the lead portion can be prevented. Furthermore, in this case, thermocompression bonding is not performed on the first region (mounting portion), so it is possible to ensure sufficient solder wettability in the first region, and sufficient connection reliability can be ensured between the coil device and the mounting board.

[0016] Preferably, a step is formed on the surface of the core on which the electrodes are formed, and the first and second regions are disposed adjacent to each other, with the second region positioned lower than the first region via the step. This configuration allows the first and second regions to be spaced apart along the height direction of the step by a distance corresponding to the height of the step. Therefore, when the lead-out portion is bonded to the second region by, for example, thermocompression bonding, heat (radiant heat) applied to the second region is less likely to reach the first region, ensuring sufficient solder wettability of the first region.

[0017] Preferably, the electrode has a step region formed in the step portion, and the conductive paste layer is formed from the first region to the step region. With this configuration, it is possible to ensure a sufficient thickness and area of ​​the conductive paste layer, strengthen the function of the conductive paste layer as a buffer layer, and effectively prevent solder cracks caused by differences in thermal stress between the solder and the plating layer.

[0018] Preferably, the step portion has an inclined surface, and the thickness of the conductive paste layer decreases toward the second region. By forming an inclined surface on the step portion, it is possible to separate the first region and the second region by a distance corresponding to the inclination angle of the inclined surface. Therefore, when the lead portion is bonded to the second region, for example, by thermocompression, heat (radiant heat) applied to the second region is less likely to reach the first region, thereby ensuring sufficient solder wettability of the first region. Furthermore, by decreasing the thickness of the conductive paste layer toward the second region, it is possible to effectively prevent deformation of the electrode near the second region when the lead portion is bonded to the second region, for example, by thermocompression.

[0019] Preferably, the core has a winding core portion to which the coil can be attached and a flange portion formed at an axial end of the winding core portion, and the electrode is formed on a surface of the flange portion. With such a core (drum core), it is possible to easily form an electrode having a first region and a second region on the flange portion, thereby facilitating the manufacture of the coil device.

[0020] Preferably, the first region and the second region are arranged adjacent to each other in a direction perpendicular to the axial direction of the winding core, the first region continuously extends a predetermined length from one end of the flange to the other end in the direction perpendicular to the axial direction of the winding core, and the width of the first region in the direction perpendicular to the axial direction of the winding core is larger than the width of the second region in the direction perpendicular to the axial direction of the winding core. This configuration allows the area of ​​the first region to be larger than the area of ​​the second region, thereby ensuring a sufficient area for the first region (mounting portion). This ensures sufficient connection reliability between the electrode (first region) and the mounting board.

[0021] Preferably, the second region is located on the mounting surface side of the core together with the first region. With this configuration, the lead portion of the coil arranged in the second region (plated layer) can be prevented from being exposed to the outside, and the lead portion can be protected.

[0022] Preferably, the lead-out portion of the coil is recessed in the plating layer, and at least a part of the lead-out portion of the coil is exposed from the plating layer. With this configuration, the lead-out portion of the coil can be pressed against the electrode, and sufficient connection strength can be ensured between the lead-out portion of the coil and the electrode.

[0023] Preferably, the core contains ferrite particles or metal particles, which can improve the magnetic properties of the coil device. [Brief explanation of the drawings]

[0024] [Figure 1A] FIG. 1A is a perspective view of a coil device according to a first embodiment of the present invention. [Figure 1B] FIG. 1B is a plan view of the coil device shown in FIG. 1A. [Figure 2A] FIG. 2A is a cross-sectional view taken along line IIA-IIA shown in FIG. 1B. [Figure 2B] FIG. 2B is a cross-sectional view showing a state (one example) when the lead-out portion of the coil shown in FIG. 2A is thermocompression-bonded to an electrode. [Figure 3] FIG. 3 is a perspective view of a coil device according to a second embodiment of the present invention. [Figure 4A] FIG. 4A is a cross-sectional view taken along line IVA-IVA shown in FIG. [Figure 4B] FIG. 4B is a cross-sectional view showing a state in which the lead-out portion of the coil shown in FIG. 4A is thermocompression-bonded to an electrode. [Figure 5] FIG. 5 is a perspective view of a coil device according to a third embodiment of the present invention. [Figure 6] FIG. 6 is a side view of the coil device shown in FIG. 5 as viewed from the direction A. FIG. [Figure 7] 7 is a cross-sectional view of the coil device shown in FIG. 5 taken along line VII-VII. [Figure 8A] FIG. 8A is an enlarged cross-sectional view of a portion of the electrode shown in FIG. [Figure 8B] FIG. 8B is a partially enlarged cross-sectional view of a modification of the electrode shown in FIG. 8A. [Figure 9A] FIG. 9A is a perspective view of a modified example of the coil device shown in FIG. 1A. [Figure 9B] FIG. 9B is a perspective view of another modified example of the coil device shown in FIG. 1A. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, the present invention will be described based on the embodiments shown in the drawings.

[0026] First embodiment 1A, a coil device 10 according to a first embodiment of the present invention has a chip shape and functions as, for example, an inductor. The coil device 10 includes a core 20, a coil 30, a first electrode 40, and a second electrode 50.

[0027] The X-axis shown in the drawing is an axis parallel to the axial direction of the winding core 23 of the core 20, the Y-axis is an axis perpendicular to the axial direction of the winding core 23, and the Z-axis is an axis perpendicular to the mounting surface. The mounting surface of the coil device 10 is above the Z-axis, i.e., the side where the first electrode 40 and the second electrode 50 are located.

[0028] Core 20 is a so-called drum core, and has a first flange portion 21, a second flange portion 22, and a winding core portion 23. The size of core 20 is not particularly limited, but its length in the X-axis direction is 0.4 to 6 mm, its length in the Y-axis direction is 0.2 to 6 mm, and its length in the Z-axis direction is 0.2 to 3 mm.

[0029] The core 20 is formed from a material containing a magnetic material and a resin. Examples of the magnetic material forming the core 20 include ferrite particles or metal magnetic particles. Examples of ferrite particles include Ni-Zn ferrite and Mn-Zn ferrite. Examples of the metal magnetic particles include, but are not limited to, Fe-Ni alloy powder, Fe-Si alloy powder, Fe-Si-Cr alloy powder, Fe-Co alloy powder, Fe-Si-Al alloy powder, and amorphous iron. Examples of the resin forming the core 20 include, but are not limited to, epoxy resin, phenolic resin, polyester resin, polyurethane resin, polyimide resin, other synthetic resins, and other non-magnetic materials. The core 20 may also be a sintered body of a metal magnetic material.

[0030] The winding core 23 is columnar and has a substantially rectangular cross-sectional shape. The cross-sectional shape of the winding core 23 is not particularly limited, and may be circular, substantially octagonal, or another polygonal shape. The coil 30 is attached to the outer peripheral surface of the winding core 23. The wire forming the coil 30 may be, for example, one in which a core material made of a good conductor such as copper (Cu) is covered with an insulating material made of imide-modified polyurethane or the like, and the outermost surface is further covered with a thin resin film such as polyester.

[0031] The first flange 21 is formed at one axial end of the winding core 23, and the second flange 22 is formed at the other axial end of the winding core 23. The first flange 21 has a substantially rectangular parallelepiped shape, and the second flange 22 has a shape that is rotationally symmetrical with respect to the first flange 21 by 180 degrees.

[0032] A step portion 210 is formed on the upper surface (mounting surface) of the first flange 21 on which the first electrode 40 is formed. The step portion 210 is formed on one side in the Y-axis direction relative to the center of the first flange 21 in the Y-axis direction. The step portion 210 also extends from one end of the first flange 21 in the X-axis direction to the other end. A step upper surface 212 is formed on one side in the Y-axis direction of the first flange 21, via the step portion 210. A step lower surface 213 is formed on the other side in the Y-axis direction of the first flange 21, via the step portion 210. The step portion 210 has an inclined surface 211, and the step upper surface 212 and the step lower surface 213 are connected via the inclined surface 211.

[0033] A step portion 220 is formed on the upper surface (mounting surface) of the second flange portion 22 on which the second electrode 50 is formed. When viewed from the Z-axis direction, the step portion 220 is disposed on a diagonal line of the step portion 210. The step portion 220 has the same shape as the step portion 210, and therefore a detailed description of the shape of the step portion 220 will be omitted.

[0034] The first electrode 40 is formed on the upper surface of the first flange 21. The first electrode 40 has a first region 41, a second region 42, and a step region 43. These are located on the mounting surface side of the core 20 and are continuously (integrally) connected along the Y-axis direction. The edges of the first electrode 40 wrap around the inner and outer end faces of the first flange 21 in the X-axis direction and both side faces in the Y-axis direction.

[0035] The first region 41 and the second region 42 are formed adjacent to each other along the Y-axis direction, and the step region 43 is formed on the inclined surface 211 of the step portion 210. More specifically, the first region 41 is formed on a step upper surface 212 formed on one side of the step portion 210 in the Y-axis direction. The first region 41 extends continuously along the Y-axis direction for a predetermined length from one end of the first flange portion 21 in the Y-axis direction to the position of the step portion 210. The first region 41 functions as a connection surface (mounting portion) with a mounting board, and is connected to the mounting board by, for example, solder.

[0036] The second region 42 is formed on a stepped upper surface 213 formed on the other side of the stepped portion 210 in the Y-axis direction. That is, the second region 42 is located at a lower position than the first region 41, via the stepped portion 210. The second region 42 extends continuously along the Y-axis direction for a predetermined length from the other end of the first flange portion 21 in the Y-axis direction to the position of the stepped portion 210. The second region 42 functions as a connecting portion with the lead-out portion 30a of the coil 30, and the lead-out portion 30a is connected to the second region 42, for example, by thermocompression bonding.

[0037] In this embodiment, the first region 41 and the second region 42 can be spaced apart along the height direction of the step portion 210 by a distance corresponding to the height of the step portion 210. Therefore, when the lead-out portion 30a is thermocompression-bonded to the second region 42, the heat (radiant heat) applied to the second region 42 is less likely to reach the first region 41, and the solder wettability of the first region 41 can be sufficiently ensured.

[0038] Also, the distance between the first region 41 and the second region 42 can be separated in the Y-axis direction by a distance corresponding to the inclination angle of the inclined surface 211. Therefore, also in this regard, the heat (radiant heat) applied to the second region 42 is less likely to reach the first region 41, and the solder wettability of the first region 41 can be sufficiently ensured.

[0039] The first electrode 40 is formed in a stepped (tapered) shape in the stepped region 43 (the inclined surface 211 of the stepped portion 210) so as to follow the upper surface shape of the first flange portion 21. As shown in FIG. 2A, the inclination angle of the stepped region 43 is different (larger) from the inclination angle of the inclined surface 211, but may be substantially equal.

[0040] As shown in FIG. 1B, the width W1 in the Y-axis direction of the first region 41 is larger than the width W2 in the Y-axis direction of the second region 42. The ratio W2 / W3 of the width W2 in the Y-axis direction of the second region 42 to the width W3 in the Y-axis direction of the first flange portion 21 is preferably 1 / 16 < W2 / W3 < 1 / 2, and more preferably 1 / 8 < W2 / W3 < 1 / 3. Thereby, it becomes possible to provide the second region 42 with a sufficient area for connecting the lead-out portion 30a of the coil 30, and the lead-out portion 30a can be easily thermocompression-bonded to the second region 42. Also, the area of the first region 41 can be made larger than the area of the second region 42, and it is possible to sufficiently secure the area of the first region 41 that functions as a mounting portion. Therefore, the connection reliability between the first electrode 40 (the first region 41) and the mounting substrate can be sufficiently ensured.

[0041] The second electrode 50 is formed on the upper surface of the second flange portion 22. The second electrode 50 has a first region 51, a second region 52, and a stepped region 53. Since the shape and function of the second electrode 50 (the first region 51, the second region 52, and the stepped region 53) are the same as the shape and function of the first electrode 40 (the first region 41, the second region 42, and the stepped region 43), detailed description thereof will be omitted. Note that the lead-out portion 30b of the coil 30 is connected to the second region 52 of the second electrode 50 by thermocompression bonding.

[0042] 2A, the first region 41 includes, in order (from the position of the upper surface of the first flange portion 21), a base electrode layer 40a, a conductive paste layer (conductive resin layer) 40b, and a plating layer 40c. The second region 42 includes, in order, a base electrode layer 40a and a plating layer 40c. The stepped region 43 includes, in order, a base electrode layer 40a, a conductive paste layer (conductive resin layer) 40b, and a plating layer 40c.

[0043] That is, in this embodiment, the base electrode layer 40a and the plating layer 40c are provided in common to the first region 41, the second region 42, and the stepped region 43. On the other hand, the conductive paste layer 40b is provided only in the first region 41 and the stepped region 43.

[0044] The base electrode layer 40a is made of a baked electrode and is formed by applying a conductive paste to the upper surface of the first flange portion 21 and baking it. The conductive paste can be applied by a method such as screen printing. The thickness of the base electrode layer 40a is not particularly limited, but is preferably 5 to 20 μm. The base electrode layer 40a may be made of multiple layers.

[0045] The conductive paste layer 40b is made of a conductive paste. The conductive paste layer 40b is formed by applying and curing a conductive paste on the upper surface of the base electrode layer 40a so as to cover the upper surface 212 of the step and the inclined surface 211. The conductive paste can be applied by a method such as screen printing, for example.

[0046] The conductive paste forming the conductive paste layer 40b or the base electrode layer 40a contains conductive particles and an organic binder. The conductive paste contains at least one metal selected from the group consisting of Au, Ag, Cu, Ni, C, Pd, and Ag-Pd alloys. The organic binder may be, for example, an epoxy resin, a phenol resin, an acrylic resin, a urethane resin, a silicone resin, or a polyimide resin.

[0047] Of these, it is preferable to use a silver paste containing conductive particles made of Ag and an epoxy resin as the conductive paste for forming the conductive paste layer 40b. This is because the conductive particles made of Ag have a spherical or flake-like (flat) shape and are characterized by stable conductivity, high thermal conductivity, and oxidation resistance. In addition, the epoxy resin has small volume shrinkage when hardened and has good adhesion to metals and high heat resistance. It is preferable that the conductive paste layer 40b contains a mixture of spherical conductive particles and flake-like conductive particles.

[0048] The conductive paste layer 40b contains a thermosetting resin and is therefore more flexible than, for example, the base electrode layer 40a and the plating layer 40c. Therefore, the conductive paste layer 40b functions as a buffer layer when the coil device 10 is mounted on a mounting substrate (not shown), for example, by soldering. This makes it possible to prevent solder cracks from occurring due to differences in thermal stress between the solder and the plating layer.

[0049] The thickness of the conductive paste layer 40b is not particularly limited, but is preferably 10 to 200 μm. That is, the thickness of the conductive paste layer 40b is preferably greater than the thickness of the base electrode layer 40a. By setting the thickness of the conductive paste layer 40b within the above range, the conductive paste layer 40b can fully function as a buffer layer.

[0050] It is preferable that the conductive paste layer 40b is formed not only on the top surface of the first flange portion 21 shown in FIG. 1A, but also on the inner and outer end surfaces of the first flange portion 21 in the X-axis direction and on both side surfaces in the Y-axis direction.

[0051] 2A, the conductive paste layer 40b is formed from the first region 41 (the step upper surface 212) to the step region 43 (the inclined surface 211 of the step portion 210). This makes it possible to ensure a sufficient thickness of the conductive paste layer 40b and a sufficient range along the Y-axis direction, thereby enhancing the function of the conductive paste layer 40b as a buffer layer.

[0052] The thickness of the conductive paste layer 40b may decrease toward the second region 42. For example, in the example shown in Fig. 2A, the thickness of the conductive paste layer 40b gradually decreases in the step region 43 (inclined surface 211) toward the second region 42. Therefore, in the step region 43 (inclined surface 211), the conductive paste layer 40b has a tapered shape.

[0053] The thickness of the conductive paste layer 40b may gradually decrease from the first region 41 (step upper surface 212) to the step region 43 (inclined surface 211) toward the second region 42. In this case, the conductive paste layer 40b has a tapered shape in the range from the first region 41 (step upper surface 212) to the step region 43 (inclined surface 211).

[0054] In this way, by reducing the thickness of the conductive paste layer 40b as it approaches the second region 42, deformation of the first electrode 40 in the vicinity of the second region 42 can be effectively prevented when the lead-out portion 30a of the coil 30 is, for example, thermocompression-bonded to the second region 42.

[0055] The conductive paste layer 40b preferably covers the entire inclined surface 211 (step region 43), and may partially extend to the second region 42 (step lower surface 211). However, it is preferable that the conductive paste layer 40b does not extend to the vicinity of the lead-out portion 30a of the coil 30 (at least the lower portion of the lead-out portion 30a).

[0056] The plating layer 40c includes a first plating layer 40c1 and a second plating layer 40c2. The first plating layer 40c1 is formed of Ni plating, and the second plating layer 40c2 is formed of Sn plating. However, the platings forming the first plating layer 40c1 and the second plating layer 40c2 are not limited to these and can be appropriately selected from Cu plating, Ni plating, Sn plating, Ni-Sn plating, Cu-Ni-Sn plating, Ni-Au plating, Au plating, etc. The plating layer 40c may be a single layer.

[0057] The first plating layer 40c1 is formed on the surface of the conductive paste layer 40b in the first region 41 and the stepped region 43 so as to cover the conductive paste layer 40b. The first plating layer 40c1 is also formed on the surface of the base electrode layer 40a in the second region 42 so as to cover the conductive paste layer 40b. The first plating layer 40c1 is formed by electrolytic plating or electroless plating on the surface of the conductive paste layer 40b or the base electrode layer 40a to form a plating film. The thickness of the first plating layer 40c1 is not particularly limited, but is preferably 0.1 to 15 μm.

[0058] 2A, the thickness of the first plating layer 40c1 in the second region 42 is greater than the thickness of the first plating layer 40c1 in the first region 41. However, the thickness distribution of the first plating layer 40c1 is not limited to this, and the thickness of the first plating layer 40c1 in the first region 41 may be greater than the thickness of the first plating layer 40c1 in the second region 42. Alternatively, these thicknesses may be approximately equal.

[0059] The second plating layer 40c2 is formed on the surface of the first plating layer 40c1 so as to cover it. The second plating layer 40c2 is formed by applying electrolytic plating or electroless plating to the surface of the first plating layer 40c1 to form a plating film. The thickness of the second plating layer 40c2 is not particularly limited, but is preferably 0.1 to 15 μm. Note that the thickness of the second plating layer 40c2 in the first region 41 and the thickness of the second plating layer 40c2 in the second region 42 are approximately equal, but they may be different, for example, the former thickness may be greater than the latter thickness.

[0060] The first plating layer 40c1 and the second plating layer 40c2 are formed from the first region 41 to the second region 42 so as to straddle the stepped region 43. The first plating layer 40c1 and the second plating layer 40c2 are formed in a stepped shape in the stepped region 43 (the inclined surface 211 of the stepped portion 210) so as to fit the shape of the upper surface of the first flange portion 21.

[0061] In the first region 41, the second plating layer 40c2 is connected to the mounting substrate. Because the second plating layer 40c2 has relatively high solder wettability, connecting the first electrode 40 to the mounting substrate via the second plating layer 40c2 can sufficiently ensure connection reliability between the coil device 10 and the mounting substrate. Note that the second plating layer 40c2 in the stepped region 43 may not substantially contribute to connection with the mounting substrate.

[0062] In the second region 42, the lead portion 30a of the coil 30 is connected to the upper surface of the second plating layer 40c2. Therefore, in this embodiment, the lead portion 30a is arranged on the plating layer 40c in the second region 42. The second region 42, together with the first region 41, is located on the mounting surface side of the core 20. Therefore, when the coil device 10 is mounted on a mounting board, the lead portion 30a arranged in the second region 42 (plating layer 40c) is prevented from being significantly exposed to the outside, and the lead portion 30a can be protected.

[0063] In order to prevent the lead portion 30a from coming into contact with the mounting board when the coil device 10 is mounted on the mounting board, the step height of the first electrode 40 in the step region 43 (the step height of the plating layer 40c formed in a stepped shape) is made larger than the wire diameter of the lead portion 30a. The step height of the first electrode 40 in the step region 43 is preferably three times or more the wire diameter of the lead portion 30a.

[0064] As shown in FIG. 2B, when the lead portion 30a on the second plating layer 40c2 shown in FIG. 2A is thermocompression-bonded using a jig (a component indicated by a two-dot chain line in FIG. 2A), the lead portion 30a sinks into the first electrode 40. In the example shown in FIG. 2B, the lead portion 30a sinks (is sunken) into the second plating layer 40c2, and a portion (top) of the lead portion 30a is exposed from the second plating layer 40c2. Around the lead portion 30a, the second plating layer 40c2 is drawn toward the lead portion 30a, and the second plating layer 40c2 protrudes in a convex (tapered) shape toward the lead portion 30a. The top of the lead portion 30a is approximately flush with the upper surface of the second plating layer 40c2.

[0065] The sides of the lead portion 30a are surrounded (covered) by the second plating layer 40c2. The lower portion of the lead portion 30a is substantially connected to the first plating layer 40c1, but may be connected to the second plating layer 40c2 or the base electrode layer 40a. The connection position of the lower portion of the lead portion 30a can be adjusted by the pressure strength of the jig during thermocompression bonding.

[0066] A portion of the lead portion 30a may be recessed to the position of the first plating layer 40c1. In this case, the lower portion of the lead portion 30a may be connected to the base electrode layer 40a or the first plating layer 40c1.

[0067] In this way, by sinking the lead portion 30a into the plating layer 40c, it becomes possible to press the lead portion 30a against the first electrode 40, thereby ensuring sufficient connection strength between the lead portion 30a and the first electrode 40.

[0068] 1A is the same as the cross-sectional structure of the first electrode 40 shown in Figures 2A and 2B, and the description of the first electrode 40 is applicable. Therefore, a description of the cross-sectional structure of the second electrode 50 will be omitted.

[0069] As shown in FIG. 1B, the second region 42 (connection portion) of the first electrode 40 and the second region 52 (connection portion) of the second electrode 50 are arranged diagonally when viewed in the Z-axis direction, but they may also be arranged on the same side in the Y-axis direction.

[0070] Next, a method for manufacturing the coil device 10 will be described. First, a core 20 having a shape as shown in Fig. 1A is prepared. Next, a first electrode 40 and a second electrode 50 are formed on the upper surface (mounting surface) of the first flange 21 and the upper surface (mounting surface) of the second flange 22 of the core 20, respectively, as follows.

[0071] That is, as shown in FIG. 2A, a conductive paste (e.g., Ag paste) is applied to the upper surface of the first flange portion 21 (step upper surface 212, inclined surface 211, and step lower surface 213) by a method such as screen printing, and then baked at a predetermined temperature to form the base electrode layer 40a.

[0072] Next, at the positions of the first region 41 (step upper surface 212) and the step region 43 (inclined surface 211), a conductive paste (e.g., Ag paste) is applied to the upper surface of the base electrode layer 40a by a method such as screen printing so as to cover the layer, and then cured to form a conductive paste layer 40b.

[0073] Next, at the positions of the first region 41 (step upper surface 212), the step region 43 (inclined surface 211) and the second region 42 (step lower surface 213), a Ni plating film is formed on the upper surface by a method such as electrolytic plating or electroless plating so as to cover the conductive paste layer 40b and the base electrode layer 40a, thereby forming a first plating layer 40c1.

[0074] Next, at the positions of the first region 41 (step upper surface 212), the step region 43 (inclined surface 211) and the second region 42 (step lower surface 213), a Sn plating film is formed on the upper surface by a method such as electrolytic plating or electroless plating so as to cover the first plating layer 40c1, thereby forming the second plating layer 40c2.

[0075] The second electrode 50 shown in FIG. 1A is formed in the same manner as the first electrode 40. Next, as shown in FIG. 1A, a wire is wound around the winding core portion 23 of the core 20 to form the coil 30. Next, as shown in FIGS. 2A and 2B, in the second region 42, the lead portion 30a of the coil 30 is connected from above the second plating layer 40c2 by, for example, thermocompression bonding, so that the lead portion 30a is conductively bonded to the first electrode 40. The lead portion 30b is also conductively bonded to the second electrode 50 in the same manner as the lead portion 30a. At this time, the coating on the wire is sublimated, so that no coating residue remains inside the first electrode 40 or the second electrode 50, even if the coating on the wire is not removed.

[0076] As described above, in the coil device 10 of this embodiment, after forming a laminated electrode including the base electrode layer 40a, the conductive paste layer 40b, and the plating layer 40c shown in FIG. 2A, the coil 30 is attached to the winding core 23 shown in FIG. 1A and the lead portion 30a (lead portion 30b) is connected to the second region 42 (second region 52). In this case, since the coil 30 is not attached to the core 20 when the plating layer 40c is formed, there is no risk of the plating liquid permeating into the coil 30, and deterioration of the quality of the coil device 10 due to the permeation of the plating liquid can be prevented. Furthermore, since there is no risk of the plating liquid permeating into the coil 30, there is no need to provide the coil device 10 with a means for protecting the coil 30 from the permeation of the plating liquid (for example, the resin coating layer described in Patent Document 1), which simplifies the manufacturing process of the coil device 10.

[0077] 2A , when the conductive paste layer 40a is provided only in the first region 41 of the first and second regions 41 and 42 (i.e., when the conductive paste layer 40b is not provided in the second region 42), the second region 42 is less likely to deform than the first region 41, and the lead portion 30a is less likely to peel off from the second region 42. Therefore, when the lead portion 30a is bonded to the second region 42 by, for example, thermocompression, deformation of the second region 42 or peeling of the lead portion 30a from the first electrode 40 can be prevented, and deterioration in the quality of the coil device 10 due to deformation of the first electrode 40 (second region 41) or peeling of the lead portion 30a can be prevented. Furthermore, in this case, thermocompression bonding is not performed on the first region 41 (mounting portion), so it is possible to ensure sufficient solder wettability in the first region 41, and it is possible to ensure sufficient connection reliability between the coil device 10 and the mounting board.

[0078] The inventors measured the adhesive strength between the conductive paste layer 40b and the first plating layer 40c1 in the first region 41 (mounting region) before and after thermocompression bonding of the lead portion 30a to the second region 42 (connecting region). The results showed that before thermocompression bonding, peeling occurred between the conductive paste layer 40b and the first plating layer 40c1 when a load of 9.47 N was applied to the first region 41. On the other hand, after thermocompression bonding, peeling occurred between the conductive paste layer 40b and the first plating layer 40c1 when a load of 9.79 N was applied to the first region 41. This confirmed that the first region 41 is hardly affected by the thermocompression bonding of the lead portion 30a to the second region 42 (the effect of radiant heat), and that deterioration of the first region 41 due to this effect can be effectively prevented.

[0079] Second embodiment 3 shows a coil device 10A according to a second embodiment of the present invention, which is similar in configuration to the first embodiment described above, except for the following differences: In the drawings, members common to the first embodiment are designated by the same reference numerals, and detailed descriptions thereof will be omitted.

[0080] The coil device 10A has a core 20A, a first electrode 40A, and a second electrode 50A. The core 20A has a first flange 21A and a second flange 22A. The first flange 21A differs from the first flange 21 (FIG. 1A) in the first embodiment in that a step 210 is not formed on the upper surface of the first flange 21A. The second flange 22A also differs from the second flange 22 (FIG. 1A) in the first embodiment in that a step 220 is not formed on the upper surface of the second flange 21A. Therefore, the upper surfaces of the first flange 21A and the second flange 22A are flat.

[0081] First electrode 40A does not have step region 43 (FIG. 1A) and has a flat shape corresponding to the top surface shape of first flange 21 A. Second electrode 50A does not have step region 53 (FIG. 1A) and has a flat shape corresponding to the top surface shape of second flange 22A.

[0082] As shown in FIG. 4A, the first electrode 40A includes, in order from the upper surface of the first flange portion 21A, a base electrode layer 40a, a conductive paste layer 40b, and a plating layer 40c. The plating layer 40c includes a first plating layer 40c1 and a second plating layer 40c2. In this embodiment, this electrode structure is continuously formed from one end to the other end of the first flange portion 21A in the Y-axis direction shown in FIG. 3. That is, unlike the first embodiment, the first electrode 40A does not include an electrode structure corresponding to the second region 42 (FIG. 2A), and the conductive paste layer 40b is provided over the entire area of ​​the first electrode 40A.

[0083] Therefore, as shown in Fig. 4A, the conductive paste layer 40b is present at the position of the connecting wire portion to which the lead portion 30a of the coil 30 is connected. As shown in Fig. 4B, when the lead portion 30a on the second plating layer 40c2 shown in Fig. 4A is thermocompression-bonded with a jig, the lead portion 30a sinks into the first electrode 40A. The lower portion of the lead portion 30a is substantially connected to the first plating layer 40c1, but may also be connected to the second plating layer 40c2, the conductive paste layer 40b, or the base electrode layer 40a.

[0084] The shape and function of the second electrode 50A are the same as those of the first electrode 40A, and therefore detailed description thereof will be omitted. The lead-out portion 30b of the coil 30 is connected to the second electrode 50A by thermocompression bonding.

[0085] 3, the lead-out portions 30a and 30b are formed at the centers of the first electrode 40A and the second electrode 50A, respectively, in the Y-axis direction, but are preferably formed at the ends in the Y-axis direction. The lead-out portions 30a and 30b may be connected to the first electrode 40A and the second electrode 50A, respectively, so as to be diagonally opposite each other when viewed in the Z-axis direction. Alternatively, the lead-out portions 30a and 30b may be connected to the first electrode 40A and the second electrode 50A, respectively, so as to be located on the same side in the Y-axis direction when viewed in the Z-axis direction.

[0086] This embodiment also provides the same effects as the first embodiment. That is, when the coil device 10A is mounted on a mounting board by, for example, soldering, the conductive paste layer 40b functions as a buffer layer to prevent solder cracks from occurring. Furthermore, the high solder wettability of the plating layer 40c improves the connection reliability between the coil device 10A and the mounting board.

[0087] Furthermore, the electrode structure of the first electrode 40A and the second electrode 50A can be obtained by, for example, forming a laminated electrode including the base electrode layer 40a, the conductive paste layer 40b, and the plating layer 40c, and then attaching the coil 30 to the core 20A and connecting the lead portions 30a and 30b to the first electrode 40A and the second electrode 50A. This makes it possible to prevent quality degradation of the coil device 10 due to infiltration of plating liquid into the coil 20 and to simplify the manufacturing process of the coil device 10.

[0088] Third embodiment 5 shows a coil device 10B according to a third embodiment of the present invention, which is similar in configuration to the first embodiment described above, except for the following differences: In the drawings, members common to the first embodiment are designated by the same reference numerals, and detailed descriptions thereof will be omitted.

[0089] The coil device 10B has a core 20B, a first electrode 40B, and a second electrode 50B. The core 20B has a first flange 21B and a second flange 22B. The core 20B is a so-called vertical drum core in which the winding core is disposed substantially perpendicular to the mounting surface. The first flange 21B and the second flange 22B have the same shape and are substantially octagonal when viewed from the Z-axis direction. However, the shapes of the first flange 21B and the second flange 22B are not limited to this and may be circular, elliptical, rectangular, or other polygonal when viewed from the Z-axis direction.

[0090] The first electrode 40B is formed on one side in the X-axis direction of the core 20B, straddling the outer peripheral surface (circumferential side surface) 222 and outer end surface 223 of the second flange portion 22B. The second electrode 40B is formed on the other side in the X-axis direction of the core 20B, straddling the outer peripheral surface (circumferential side surface) 222 and outer end surface 223 of the second flange portion 22B.

[0091] 6 and 7, the first electrode 40B spans a first surface 222a of the outer peripheral surface 222, a second surface 222b located on the opposite side of the first surface 222a in the Y-axis direction, and the outer end surface 223. The first electrode 40B has a first region 41, a second region 42, and an auxiliary region 44. As in the first embodiment, the first region 41 functions as a mounting portion, and the second region 42 functions as a connecting portion. The auxiliary region 44 functions, for example, as a solder fillet forming portion.

[0092] The first region 41 is formed on the outer end surface 223, the second region 42 is formed on the first surface 222a, and the auxiliary region 43 is formed on the second surface 222b. As shown in Fig. 8A, the first region 41 includes, in order (from the position of the outer end surface 223), a base electrode layer 40a, a conductive paste layer 40b, and a plating layer 40c. The plating layer 40c includes a first plating layer 40c1 and a second plating layer 40c2.

[0093] In the example shown in FIG. 8A, the thickness of the conductive paste layer 40b gradually decreases toward the corner between the first surface 222a and the outer end surface 223, and the conductive paste layer 40b has a tapered shape.

[0094] The second region 42 includes, in order from the position of the first surface 222a, a base electrode layer 40a and a plating layer 40c. The plating layer 40c includes a first plating layer 40c1 and a second plating layer 40c2. The second region 42 extends along the Z-axis direction along the first surface 222a. The lead portion 30a of the coil 30 is led out along the second region 42 and connected to the second plating layer 40c2 by, for example, thermocompression bonding. The lead portion 30a, which is thermocompression bonded from above the second plating layer 40c2, is embedded in the first electrode 40B in a manner as shown in FIG. 2B.

[0095] 8A, the thickness of the first plating layer 40c1 is greater in the second region 42 than in the first region 41, but the thickness distribution of the first plating layer 40c1 is not limited to this. They may be approximately equal, or the thickness of the first plating layer 40c1 may be greater in the first region 41 than in the second region 42. Furthermore, similar to the first electrode 40 of the first embodiment shown in FIG. 2A, the overall thickness of the first electrode 40B may be greater in the first region 41 than in the second region 42.

[0096] 8B, the conductive paste layer 40b may be formed over the entire first electrode 40B, from the outer end surface 223 of the first flange 21 to the outer peripheral surface 222 (first surface 222a and second surface 222b). The electrode structure of the auxiliary region 44 (FIG. 7) may be the electrode structure of the second region 42 shown in FIG. 8A, or the electrode structure of the first region 41 shown in FIG. 8A. In the latter case, when a solder fillet is formed in the auxiliary region 44, the conductive paste layer 40b functions as a buffer layer, thereby preventing solder cracks from occurring due to differences in thermal stress between the solder and the plating layer 40c.

[0097] 5 is identical in shape and function to the first electrode 40B, and therefore will not be described in detail. The lead-out portion 30b of the coil 30 is connected to the second electrode 50B by thermocompression bonding.

[0098] In this embodiment, too, it is possible to obtain the same effects as in the first embodiment. In addition, in this embodiment, as shown in Fig. 6, the second region 42 (connecting portion) is located on a surface (the outer peripheral surface 222 of the second flange portion 22) different from the first region 41 (mounting portion), so that it is possible to ensure a sufficient area for the first region 41, and it is possible to ensure sufficient connection reliability between the coil device 10B and the mounting board.

[0099] The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the present invention.

[0100] In the above embodiments, examples of application of the present invention to inductors have been described, but the present invention may also be applied to coil devices other than inductors (for example, transformers and common mode filters (chokes)).

[0101] In the first embodiment described above, as shown in Fig. 1A, the width in the Y-axis direction of the first region 41 is larger than the width in the Y-axis direction of the second region 42. However, as shown in Fig. 9A, the width in the Y-axis direction of the second region 42 may be larger than the width in the Y-axis direction of the first region 41. Similarly, the width in the Y-axis direction of the second region 52 may be larger than the width in the Y-axis direction of the first region 51.

[0102] In the first embodiment, as shown in FIG. 1A, the second region 42 is formed at the end of the first flange 21 in the Y-axis direction. However, as shown in FIG. 9B, the second region 42 may be formed in the center of the first flange 21 in the Y-axis direction. In the example shown in FIG. 9B, the first electrode 40 includes two first regions 41 and a second region 42, and the second region 42 is disposed so as to be sandwiched between the first region 41 formed on one side in the Y-axis direction and the first region 41 formed on the other side in the Y-axis direction. Similarly, the second electrode 50 may be formed in the center of the second flange 22 in the Y-axis direction.

[0103] In the first embodiment described above, the lead portion 30a of the coil 30 is connected to the second region 42 of the first electrode 40 shown in FIG. 1A by thermocompression bonding. However, the lead portion 30a may be connected to the second region 42 by a method other than thermocompression bonding. Such methods include ultrasonic bonding, resistance brazing, and ultraviolet curable resin bonding. The same applies to the case where the lead portion 30b of the coil 30 is connected to the second region 52 of the second electrode 50. The same applies to the second and third embodiments described above.

[0104] In the first embodiment, the step portion 210 and the step portion 220 may be omitted from the upper surfaces of the first flange portion 21 and the second flange portion 22 shown in FIG. 1A, respectively. [Explanation of symbols]

[0105] 10, 10A, 10B... Coil device 20, 20A, 20B...Core 21,21A,21B…1st collar part 210...Step 211…Slope surface 22,22A,22B…Second collar part 220...Step 221…Slope surface 222...Outer surface 223...Outer end surface 23...Core 30...Coil 30a, 30b...Lead section 40,40A,40B…1st electrode 40a...Base electrode layer 40b...Conductive paste layer 40c...plated layer 40c1...First plating layer 40c2: Second plating layer 41...First area 42…Second area 43...Step area 44…Auxiliary area 50,50A,50B…2nd electrode 51…First area 52…Second area 53...Step area

Claims

1. A coil and a core having a winding core portion to which the coil is attached and a flange portion provided on the winding core portion; an electrode formed on a mounting surface of the flange portion and on a side surface perpendicular to the mounting surface, the electrode being connected to a lead-out portion of the coil; the winding core portion extends in a direction perpendicular to the mounting surface, the electrode has a first region formed on the mounting surface and a second region formed on the side surface, the first region includes, in order, a base electrode layer, a conductive paste layer, and a plating layer; the second region includes, in order, the base electrode layer and the plating layer; the lead portion is disposed on the plating layer in the second region, the plating layer includes a first plating layer and a second plating layer covering the first plating layer; a thickness of the first plating layer in the second region is greater than a thickness of the first plating layer in the first region; A coil device in which a recess is formed at a position spaced from the connection portion between the second plating layer and the draw-out portion so that the thickness of the second plating layer in the second region is thinner than the thickness of the second plating layer in the first region.

2. A coil and a core having a winding core portion to which the coil is attached and a flange portion provided on the winding core portion; an electrode formed on the entire mounting surface of the flange portion and connected to a lead-out portion of the coil; a step portion having an inclined surface is formed on the mounting surface, the electrode has a first region, a second region located at a position lower than the first region across the step portion, and a step region located between the first region and the second region so as to be adjacent to the first region and the second region and formed in the step portion; the first region includes, in order, a base electrode layer, a conductive paste layer, and a plating layer; the second region includes, in order, the base electrode layer and the plating layer; the step region includes, in order, the base electrode layer, the conductive paste layer, and the plating layer; the lead portion is disposed on the plating layer in the second region, the conductive paste layer is formed from the first region to the stepped region, and extends along the inclined surface in the stepped region; the plating layer includes a first plating layer and a second plating layer covering the first plating layer; a thickness of the first plating layer in the second region is greater than a thickness of the first plating layer in the first region; A coil device in which a recess is formed at a position spaced from the connection portion between the second plating layer and the draw-out portion so that the thickness of the second plating layer in the second region is thinner than the thickness of the second plating layer in the first region.

3. 3. The coil device according to claim 1, wherein the thickness of the conductive paste layer decreases toward the second region.

4. the first region extends continuously for a predetermined length from one end to the other end of the flange portion along a direction perpendicular to the axial direction of the winding core portion, The coil device according to claim 2 , wherein the width of the first region along a direction perpendicular to the axial direction of the winding core portion is larger than the width of the second region along the direction perpendicular to the axial direction of the winding core portion.

5. The lead-out portion of the coil is embedded in the plating layer, 5. The coil device according to claim 1, wherein at least a portion of the lead-out portion of the coil is exposed from the plating layer.

6. 6. The coil device according to claim 1, wherein the core contains ferrite particles or metal particles.

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