Inductor and method for manufacturing inductor

Abstract

To suppress formation of an external electrode on an insulating coating of a lead wire of a lead-out portion on a surface of an element body, thereby suppressing recesses in a surface of the external electrode and suppressing entry of water into the external electrode.SOLUTION: An inductor includes: a coil conductor having a winding part formed by winding a lead wire and a pair of lead-out portions led out from the winding part; an element body containing magnetic particles and a resin and enclosing the coil conductor; and an external electrode connected to an exposed portion, of each lead-out portion, exposed from the surface of the element body. In an area with no exposed portion on the surface of the element body, the inductor includes a low conductivity layer having a lower conductivity than the external electrode, at a portion between the surface of the element body and the external electrode.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an inductor and a method for manufacturing an inductor. [Background technology]

[0002] Patent Document 1 describes an inductor having a coil conductor, an element body containing magnetic particles and resin and enclosing the coil conductor, and a pair of external electrodes electrically connected to the ends of the coil conductor. In this inductor, the surface of the lead-out portion of the coil conductor is exposed on the surface of the element body, and a plating layer is formed on the portion of the element body surface where the external electrodes will be formed after the resin contained in the element body is removed. This electrically connects the magnetic particles contained in the element body, the lead-out portion, and the external electrodes including the plating layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-58418 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned conventional inductors, as the external dimensions are reduced, the thickness of the element body portion interposed between the winding portion of the coil conductor embedded inside the element body and the external electrode, and between the intermediate portion of the coil conductor extending from the winding portion to the draw-out portion and the external electrode, becomes thinner, and this thinner element body portion can become a factor limiting the withstand voltage (hereinafter also referred to as breakdown voltage) of the inductor.

[0005] The object of the present invention is to improve the voltage resistance performance of an inductor having a coil conductor embedded in a body containing magnetic particles and resin, by improving the insulation between the part of the coil conductor that is inside the body and the external electrode on the surface of the body. [Means for solving the problem]

[0006] One aspect of the present invention is an inductor comprising: a coil conductor having a winding portion around which a conducting wire is wound and a pair of lead-out portions led out from the winding portion; a base body containing magnetic particles and resin and containing the coil conductor; and external electrodes connected to exposed portions of the lead-out portions that are exposed from the surface of the base body, and in areas of the surface of the base body where the exposed portions of the lead-out portions are not present, a low conductivity layer having a lower conductivity than the external electrodes is present between the surface of the base body and the external electrodes. Another aspect of the present invention is a coil conductor forming step of producing a coil conductor having a winding portion around which a conducting wire is wound and a pair of lead portions led out from the winding portion; an element body molding step of embedding the coil conductor in an element body containing magnetic particles and resin so that the lead portions of the coil conductor are exposed from the surface of the element body; a surface treatment step of irradiating laser light onto planned electrode locations on the surface of the element body, including exposed portions of the lead portions exposed from the element body, to remove part of the resin on the surface of the element body at the planned electrode locations; and a plating layer formation step of forming an external electrode by plating at the intended electrode location, in which, after completion of the surface treatment step, the intended electrode location of the element body is oxidized in an oxygen atmosphere for a predetermined period of time, and then the element body is immersed in an aqueous solution of a phosphorus compound to form a low conductivity layer having a lower conductivity than copper on the surface of the element body at the intended electrode location, and a copper plating layer constituting the external electrode is formed on the exposed portion of the lead-out portion and on the low conductivity layer at the intended electrode location. [Effects of the Invention]

[0007] According to the present invention, in an inductor having a coil conductor embedded in a body containing magnetic particles and resin, it is possible to improve the insulation between the part of the coil conductor that is inside the body and the external electrode on the surface of the body, thereby improving the voltage resistance performance. [Brief explanation of the drawings]

[0008] [Figure 1]1 is a perspective view of an inductor according to an embodiment of the present invention, viewed from above; [Figure 2] FIG. 2 is a perspective view of the inductor as viewed from the bottom side. [Figure 3] FIG. 2 is a perspective view showing the internal configuration of an inductor. [Figure 4] 4 is a planar perspective view of the inductor shown in FIG. 3 as viewed from the top surface side. [Figure 5] FIG. 5 is a VV cross-sectional view of the inductor shown in FIG. [Figure 6] FIG. 6 is a partial detailed view of part C of the inductor shown in FIG. 5. [Figure 7] 7 is an example of an enlarged cross-sectional photograph of a portion of an inductor corresponding to portion D shown in FIG. 6. [Figure 8] 1A to 1C are diagrams illustrating a manufacturing process of an inductor. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [1. Inductor configuration] First, the configuration of the inductor 1 according to this embodiment will be described. [1.1 Overall structure of inductor] FIG. 1 is a perspective view of an inductor 1 according to this embodiment as viewed from a top surface 12 side, and FIG. 2 is a perspective view of the inductor 1 as viewed from a bottom surface 10 side. The inductor 1 of this embodiment is configured as a surface-mount electronic component, and includes an element body 2 having an approximately rectangular parallelepiped shape, which is one form of an approximately hexahedral shape, and a pair of external electrodes 4 provided on the surface of the element body 2.

[0010] Hereinafter, in the element body 2, the first main surface, which is the mounting surface facing the mounting board (not shown) during mounting, is defined as the bottom surface 10, the second main surface opposite the bottom surface 10 is called the top surface 12, a pair of third main surfaces perpendicular to the bottom surface 10 are called end surfaces 14, and a pair of fourth main surfaces perpendicular to the bottom surface 10 and the pair of end surfaces 14 are called side surfaces 16. 1, the distance from the bottom surface 10 to the top surface 12 is defined as the thickness T of the element body 2, the distance between a pair of side surfaces 16 is defined as the width W of the element body 2, and the distance between a pair of end surfaces 14 is defined as the length L of the element body 2. Furthermore, the direction of the thickness T is defined as the thickness direction DT, the direction of the width W is defined as the width direction DW, and the direction of the length distance is defined as the length direction DL. The inductor 1 has a length L of 1.4 mm, a width W of 1.2 mm, and a thickness T of 0.65 mm, for example.

[0011] FIG. 3 is a perspective view showing the internal configuration of the inductor 1. As shown in FIG. The element body 2 includes a coil conductor 20 and a core 30 having a substantially hexahedral shape in which the coil conductor 20 is embedded, and is configured as a molded inductor in which the coil conductor 20 is sealed in the core 30.

[0012] The core 30 is a molded body obtained by compressing and molding a powder mixture of magnetic particles and resin into a substantially hexahedral shape by applying pressure and heat while the coil conductor 20 is enclosed therein.

[0013] The magnetic particles of this embodiment include particles of two particle sizes: first magnetic particles that are large particles with a relatively large average particle size, and second magnetic particles that are small particles with a relatively small average particle size. As a result, during compression molding, the second magnetic particles, which are small particles, enter between the first magnetic particles, which are large particles, together with the resin, thereby increasing the filling rate of the magnetic particles in the core 30 and also increasing the magnetic permeability. The average particle size (D50) of the first magnetic particles is preferably 20 μm to 68 μm, more preferably 21.4 μm to 27.4 μm. The average particle size (D50) of the second magnetic particles is preferably 1 μm to 6 μm, more preferably 1.5 μm to 1.8 μm. The magnetic particles may contain particles with different average particle sizes from the first and second magnetic particles, resulting in particles of three or more different particle sizes.

[0014] The first and second magnetic particles are both particles having a metal particle and an insulating film covering the surface of the metal particle, the insulating film having a thickness of several nanometers to several tens of nanometers. By covering the metal particle with the insulating film, the insulation resistance and the withstand voltage are increased. The first magnetic particles of this embodiment use Fe-Si-B amorphous alloy powder as the metal particles and zinc phosphate glass with a thickness of 10 nm to 50 nm as the insulating film, while the second magnetic particles of this embodiment use carbonyl iron powder as the metal particles and a silica film with a thickness of 5 nm to 15 nm as the insulating film.

[0015] In the mixed powder of this embodiment, the resin material is an epoxy resin containing a phenol alkyl type epoxy resin as a main component. The amount of the second magnetic particles in the mixed powder is, for example, 15 wt% to 30 wt%, preferably 20 wt% to 30 wt%, based on the total weight of the magnetic particles, and the resin content in the mixed powder is 2.0 wt% to 3.5 wt% based on the total weight of the mixed powder.

[0016] As shown in Fig. 3, the coil conductor 20 includes a winding portion 22 around which a conductor wire is wound, and a pair of lead-out portions 24 drawn out from the winding portion 22. Here, the portion of the conductor wire extending from the winding portion 22 to the lead-out portions 24 is referred to as an intermediate portion 23. Note that the coil conductor 20 does not necessarily have to be wound, and may be linear or meander-shaped. In these cases, the coil conductor 20 includes the linear or meander-shaped conductor wire portion instead of the winding portion 22, and a pair of intermediate portions 23 and lead-out portions 24 extending from the conductor wire portion.

[0017] The conductor wire forming the coil conductor 20 has a conductor made of copper and an insulating coating formed on the surface of the conductor. The conductor wire is, for example, a strip-shaped conductor wire (so-called rectangular conductor wire). The conductor wire has a thickness of 118 μm or less, and preferably 52 μm or more. The conductor wire has a width of 180 μm or less, and preferably 110 μm or more. The conductor wire has an aspect ratio of, for example, 1.2 or more and 3.4 or less. The insulating coating is, for example, polyurethane resin, polyester resin, epoxy resin, or polyimideamide resin, and is preferably polyimideamide resin. The insulating coating has a thickness of, for example, 3 μm.

[0018] The conductor wire may have a bonding layer on the insulating coating to bond overlapping conductor wires together in the winding portion 22. For example, the bonding layer is made of polyamide resin, and the thickness is preferably 1 μm or more and 25 μm or less, more preferably 2 μm or more and 25 μm or less, and even more preferably 2 μm or more and 4 μm or less.

[0019] The winding portion 22 of the coil conductor 20 is formed by winding a strip-shaped conductor wire (hereinafter simply referred to as a conductor wire) in a spiral shape, with both ends drawn out to the outer periphery and connected to each other at the inner periphery. In this embodiment, the winding portion 22 is configured as a two-stage spiral along its central axis. Inside the element body 2, the coil conductor 20 is embedded in the core 30 with the central axis of the winding portion 22 oriented along the thickness direction DT of the element body 2. The lead-out portions 24 extend from the winding portion 22 to each of a pair of end faces 14, with one main surface exposed from the element body 2 and the other main surface embedded in the element body 2. The intermediate portion 23 is located inside the element body 2 and corresponds to the conductor portion in the present disclosure that extends within the element body 2 from the exposed portion of the lead-out portion 24 toward the winding portion 22.

[0020] An external electrode 4 is electrically connected to the exposed portion of the lead portion 24 that is exposed from the surface of the element body 2 .

[0021] The pair of external electrodes 4 are so-called L-shaped electrodes, consisting of L-shaped members extending from each of the end faces 14 of the element body 2 to the bottom face 10. Each of the external electrodes 4 is connected to the lead-out portion 24 of the coil conductor 20 at the end face 14, and the portion extending to the bottom face 10 is electrically connected to wiring on the circuit board by an appropriate mounting means such as solder.

[0022] An element protective film (not shown) is formed on the surface of the element body 2 excluding the area of ​​the external electrodes 4. The element protective film is made of, for example, phenoxy resin and novolac resin, and contains nanosilica as a filler. The element protective film is formed on the surface of the element body 2 to a thickness of 10 μm or more and 30 μm or less.

[0023] Inductor 1 with this configuration can improve DC bias characteristics by using a soft magnetic material for the magnetic particles, and is therefore used as an electronic component in electric circuits through which large currents flow, as a choke coil in DC-DC converter circuits and power supply circuits, and as an electronic component in electronic devices such as personal computers, DVD players, digital cameras, TVs, mobile phones, smartphones, car electronics, medical and industrial machinery, etc. However, the uses of inductor 1 are not limited to these, and it can also be used in, for example, tuning circuits, filter circuits, rectifying and smoothing circuits, etc.

[0024] [1.2 Structure of the boundary between the external electrode and the element body] As described above in relation to the background art, in conventional inductors, as the external dimensions become smaller, the thickness of the element body portion interposed between the winding portion of the coil conductor embedded inside the element body and the external electrode, and between the intermediate portion of the coil conductor extending from the winding portion to the draw-out portion and the external electrode, becomes thinner, and this thinner element body portion can become a factor limiting the withstand voltage of the inductor.

[0025] For this reason, in the inductor 1 according to this embodiment, a low-conductivity layer 5 (described later) having a lower conductivity than the external electrode 4 is formed between the surface of the element body 2 and the external electrode 4, particularly in an area of ​​the surface of the element body 2 where there is no exposed portion of the lead-out portion 24. The presence of the low-conductivity layer 5 between the surface of the element body 2 and the external electrode 4 increases the insulation resistance between the portion of the coil conductor 20 present inside the element body 2 and the external electrode 4, improving the withstand voltage of the inductor 1.

[0026] FIG. 4 is a planar perspective view of the inductor 1 shown in FIGS. 1 and 3 as viewed from the top surface 12 side. In FIG. 4 , one main surface of the lead portion 24 of the coil conductor 20 is exposed on each of the left and right end faces 14 of the element body 2. The exposed portion of the lead portion 24 exposed on the end face 14 is electrically connected to the external electrode 4 formed on the surface of the element body 2. Here, the area on the surface of the element body 2 where there is no exposed portion of the lead portion 24 and where the external electrode 4 is formed is referred to as the electrode extension region A. In the example shown in FIG. 4 , the electrode extension regions A exist below and above the external electrode 4 on the left and right end faces 14. Hereinafter, when distinguishing between the two electrode extension regions A present at the bottom and top of the external electrode 4, the electrode extension region A at the bottom will be referred to as electrode extension region A1, and the electrode extension region A at the top will be referred to as electrode extension region A2.

[0027] The electrode extension region A1 is a region of the end face 14 on which the external electrode 4 is formed, which extends in a direction along the intermediate portion 23 that extends from the lead portion 24 toward the winding portion 22 into the element body 2. On the other hand, the electrode extension region A2 is a region of the end face 14 on which the external electrode 4 is formed, which extends from the end of the lead portion 24 in a direction away from the intermediate portion 23.

[0028] Fig. 5 is a VV cross-sectional view taken along the VV cross-sectional line passing through the electrode extension region A1 of the inductor 1 shown in Fig. 4. Fig. 6 is a partial detailed view of part C of the cross section shown in Fig. 5, and is a cross-sectional view of the vicinity of the electrode extension region A1 of the end face 14.

[0029] As described above, the electrode extension region A is a region on the surface of the element body 2 where there is no exposed portion of the lead portion 24 and where the external electrode 4 is formed. In this embodiment, particularly in such an electrode extension region A, a low conductivity layer 5 is disposed between the surface of the element body 2 and the external electrode 4.

[0030] 6 , in the inductor 1, a low-conductivity layer 5 having a lower conductivity than the external electrode 4 is disposed between the external electrode 4 and the end face 14 of the element body 2 in a cross section passing through the electrode extension region A1. Because this low-conductivity layer 5 has a lower conductivity than the external electrode 4, it functions as a high-resistance portion having a higher resistivity than the external electrode 4, and increases the insulation resistance between the external electrode 4 and the intermediate portion 23, which is part of the coil conductor 20, thereby increasing the withstand voltage of the inductor 1.

[0031] The low conductivity layer 5 need only be formed in at least a portion of the electrode extension region A on the surface of the element body 2, where the external electrode 4 faces a portion of the coil conductor 20 across a portion of the element body 2, and does not necessarily have to be formed over the entire electrode extension region A.

[0032] For example, the portion indicated by the symbol "B" in Figure 5, i.e., the surface portion of the element body 2 where the external electrode 4 extends from the end face 14 to the bottom face 10, is the electrode extension region A, where the external electrode 4 and the coil conductor 20 face each other across a part of the element body 2, and the provision of a low conductivity layer 5 can increase the withstand voltage of the inductor 1.

[0033] Here, from the viewpoint of increasing the withstand voltage of the inductor 1, it is preferable that the low conductivity layer 5 is formed in a portion of the electrode extension region A where the external electrode 4 and a part of the coil conductor 20 face each other more closely across the electrode extension region A.

[0034] Therefore, in the inductor 1 in this embodiment in which the lead portion 24 is exposed from a pair of opposing end faces 14 of the element body 2, it is preferable that the low conductivity layer 5 be formed in the electrode extension region A of the end face 14. This is because the end face 14 is the surface on which the intermediate portion 23 extending from the lead portion 24 faces closely to the external electrode 4 across the end face 14.

[0035] Furthermore, in an inductor 1 in which the lead portion 24 is exposed from the end face 14, it is more preferable that the low conductivity layer 5 be formed in the electrode extension region A of the end face 14 in a portion where the intermediate portion 23 extending from the lead portion 24 toward the winding portion 22 into the element body 2 faces the external electrode 4 (for example, the electrode extension region A1 shown in FIG. 4 ). This effectively suppresses dielectric breakdown between the external electrode 4 and the intermediate portion 23, which are particularly close to each other across a part of the element body 2, and improves the withstand voltage of the inductor 1.

[0036] When the external electrodes 4 are formed of copper plating layers, examples of the material for the low conductivity layer 5 include a material containing phosphorus (P) and / or a material containing iron (Fe), zinc (Zn), manganese (Mn), and / or oxygen (O) in addition to phosphorus (P). Such a material containing phosphorus can be formed, for example, by immersing the element body 2 in an aqueous solution of a phosphorus compound before forming the external electrodes 4, as shown in the manufacturing process described below.

[0037] FIG. 7 is an example of an SEM photograph (electron microscope photograph) enlarging a cross section of the fabricated inductor 1 at a portion corresponding to portion D in the cross section shown in FIG. 6. As described above, this inductor 1 includes a low-conductivity layer 5 formed by immersing the element body 2 in an aqueous solution of a phosphorus compound before the formation of the external electrodes 4. The enlarged photograph in FIG. 7 shows that the low-conductivity layer 5 is formed between the external electrodes 4 and the end surface 14 of the element body 2. SEM-EDEX analysis performed when the SEM photograph in FIG. 7 was taken confirmed that phosphorus is contained in the region of the low-conductivity layer 5.

[0038] [2. Inductor manufacturing process] FIG. 8 is a diagram showing a manufacturing process of the inductor 1. The manufacturing process of the inductor 1 includes a coil conductor forming step (S1), a preform forming step (S2), an element molding step (S3), a barrel polishing step (S4), and an external electrode forming step (S5).

[0039] The coil conductor formation step (S1) is a step of forming a coil conductor 20 from a conductive wire. In this step, the coil conductor 20 is formed into a shape having the above-mentioned winding portion 22 and a pair of lead-out portions 24 by winding the conductive wire using a winding method known as "alpha winding," for example. Alpha winding refers to a state in which the lead-out portions 24 at the start and end of the winding of the conductive wire, which functions as a conductor, are wound in two spiral stages so that they are located on the outer periphery. The number of turns of the coil conductor 20 is not particularly limited.

[0040] The preform forming step (S2) is a step of forming a preform called a tablet. The preform is formed by pressing the above-mentioned mixed powder, which is the material of the base body 2, into a solid form that is easy to handle.In this embodiment, two types of tablets are formed: a first tablet of an appropriate shape (e.g., E-shaped) with a groove into which the coil conductor 20 fits, and a second tablet of an appropriate shape (e.g., I-shaped or plate-shaped) that covers the groove of the first tablet.

[0041] In the element molding step (S3), the first tablet, the coil conductor, and the second tablet are set in a molding die, and while applying heat, pressure is applied in the overlapping direction of the first tablet and the second tablet to harden them, integrating the first tablet, the coil conductor, and the second tablet, thereby molding the element 2 in which the coil conductor 20 is enclosed in the core 30.

[0042] In this embodiment, in the element body molding step (S3), the coil conductor 20 is embedded in the element body 2 so that one main surface of the lead portion 24, which is a strip-shaped conductor, is exposed from the end surface 14 of the element body 2.

[0043] The barrel polishing step (S4) is a step of barrel polishing this molded body, and by this step, the corners of the element body 2 are rounded.

[0044] The external electrode forming step (S5) is a step of forming the external electrodes 4 on the core 30, and includes an element protective film forming step (S51), a surface treatment step (S52), and a plating layer forming step (S53).

[0045] The element protective film forming step (S51) is a step of coating the entire surface of this molded body with insulating resin.

[0046] The surface treatment step (S52) is a step of modifying the surface of the planned electrode area by irradiating the area with laser light. Here, the planned electrode area refers to the area on the surface of the core 30 where the external electrode 4 is to be formed, including the area where the lead-out portion 24 is exposed. Specifically, by irradiating the laser light, the element protective film on the surface of the core 30 and the coating layer on the lead-out portion 24 of the coil conductor 20 are removed in the planned electrode area, the resin on the surface of the core 30 is removed, and the insulating film on the surface of the magnetic particles exposed from the core 30 is removed. As a result, the exposed area of ​​the metal of the magnetic particles per unit area of ​​the surface of the core 30 is larger in the planned electrode area than in other surface areas of the core 30. In the surface treatment step (S52) of this embodiment, after the laser light irradiation, the surface of the planned electrode area is cleaned by etching, and then the entire element body 2 is washed with water.

[0047] In the plating layer formation step (S53), copper is barrel-plated onto the surface of the core 30, thereby forming a copper plating layer at the electrode locations irradiated with the laser light, thereby forming the external electrode 4. The external electrode 4 may be formed by further providing a Ni plating layer and a Sn plating layer on top of the copper plating layer. When the external electrode 4 is formed of multiple layers in this way, the conductivity of the external electrode 4 is determined by the conductivity of the layer in contact with the element body 2 (the copper plating layer in the above example), and it is sufficient that the conductivity of the low-conductivity layer 5 is lower than the conductivity of the layer in contact with the element body 2.

[0048] In this embodiment, particularly in the plating layer formation step (S53) following the surface treatment step (S52), after the element body 2 is washed with water at the end of the surface treatment step (S52), the element body 2 is left in an oxygen atmosphere (e.g., in the air) for a predetermined time (e.g., several minutes) to oxidize the electrode locations of the element body 2. The element body 2 is then immersed in an aqueous solution of a phosphorus compound to form a low-conductivity layer 5 containing P, which has a lower conductivity than copper, on the surface of the element body 2 in the electrode locations. After the formation of the low-conductivity layer 5, a copper plating layer that will constitute the external electrode 4 is formed on the exposed portions of the lead portions 24 in the electrode locations and on the low-conductivity layer 5.

[0049] Here, the aqueous solution of the phosphorus compound may be, for example, an aqueous solution of pyrophosphoric acid. Pyrophosphoric acid is widely known as a compound contained in copper plating solutions used to form the copper plating layers that constitute the external electrodes 4. Therefore, according to this manufacturing method, it is not necessary to add compounds that are not normally used in the manufacturing process of the inductor 1, so that the low conductivity layer 5 can be easily formed and an inductor 1 with excellent voltage resistance characteristics can be easily manufactured.

[0050] 3. Other Embodiments The low-conductivity layer 5 may be formed between the surface of the element body 2 and the external electrode 4 at a position where the winding portion 22 and the external electrode 4 are close to each other with part of the element body 2 sandwiched therebetween.

[0051] In the above-described embodiment, the coil conductor 20 includes, as an example, an alpha-wound winding portion 22, but the portion corresponding to the winding portion 22 may also be configured in a linear shape, a meandering shape, or the like.

[0052] In the above-described embodiment, one main surface of the lead-out portion 24 formed from the strip-shaped conductor is exposed to the end surface 14, but any part of the lead-out portion 24 (for example, the tip surface of the lead-out portion 24) may be exposed to the end surface 14 of the base body 2.

[0053] In the above-described embodiment, the coil conductor 20 is formed of a strip-shaped conductor wire, but it may also be formed of a linear conductor wire having a circular or elliptical cross section.

[0054] In the above-described embodiment, the external electrode 4 is formed as an L-shaped electrode. However, the external electrode 4 is not limited to an L-shaped electrode, and may be formed as a so-called five-sided electrode that is provided over the entire end face 14 and extends over parts of the bottom face 10, top face 12, and pair of side faces 16 adjacent to the end face 14.

[0055] All of the above-described embodiments and modifications are merely examples of one aspect of the present invention, and any modifications and applications are possible within the scope of the present invention. Furthermore, unless otherwise specified, the horizontal, vertical, and other directions, various numerical values, shapes, and materials in the above-described embodiments include a range (so-called equivalent range) that produces the same effect as those directions, numerical values, shapes, and materials.

[0056] 4. Configurations supported by the above embodiments The above-described embodiment supports the following configurations.

[0057] (Configuration 1) An inductor comprising: a coil conductor having a winding portion around which a conducting wire is wound and a pair of lead-out portions led out from the winding portion; an element body containing magnetic particles and resin and containing the coil conductor; and an external electrode connected to an exposed portion of the lead-out portion that is exposed from the surface of the element body, wherein in an area of ​​the surface of the element body where the exposed portion of the lead-out portion is not present, a low conductivity layer having a lower conductivity than the external electrode is provided between the surface of the element body and the external electrode. According to the inductor of configuration 1, the low conductivity layer interposed between the external electrode and the surface of the element body increases the insulation resistance between the portion of the coil conductor that faces each other across a part of the element body and the external electrode, thereby increasing the withstand voltage of the inductor.

[0058] (Configuration 2) An inductor as described in Configuration 1, wherein the element body has a pair of opposing end faces, the exposed portion of the lead-out portion is located at the end face of the element body, and the low conductivity layer is formed in an area of ​​the end face where the exposed portion is not present. According to the inductor of configuration 2, a low conductivity layer is disposed on the end face where the exposed portion of the lead-out portion is disposed, thereby increasing the insulation resistance between the external electrode and the conductor portion extending from the exposed portion of the lead-out portion on the end face into the body, thereby increasing the withstand voltage of the inductor.

[0059] (Configuration 3) An inductor according to configuration 2, wherein the low conductivity layer is formed on a portion of the end face where a conductor portion extending from the exposed portion of the lead-out portion along the end face into the element body faces an external electrode. According to the inductor of configuration 3, it is possible to effectively suppress dielectric breakdown between the external electrodes formed on the end faces and the conductor portions, and to more effectively improve the withstand voltage of the inductor.

[0060] (Configuration 4) An inductor according to configuration 2, wherein the element body has a mounting surface perpendicular to the pair of end faces, and the low conductivity layer is formed on the mounting surface at a position where the winding portion and the external electrode sandwich a portion of the element body. According to the inductor of configuration 4, it is possible to effectively suppress dielectric breakdown between the external electrodes formed on the mounting surface and the conductor portions, and to more effectively improve the withstand voltage of the inductor.

[0061] (Configuration 5) The inductor according to any one of configurations 1 to 4, wherein the external electrodes include copper plating layers, and the conductivity of the low conductivity layer is lower than the conductivity of copper. According to the inductor of configuration 5, when the external electrodes include a copper plating layer that is widely used in inductors that include a coil conductor using copper wire, the withstand voltage of the inductor can be effectively increased.

[0062] (Configuration 6) The inductor according to any one of configurations 1 to 5, wherein the low conductivity layer contains phosphorus (P). According to the inductor of configuration 6, the withstand voltage of the inductor can be increased by the low conductivity layer that can be easily formed by surface treatment of the element body using, for example, a compound solution containing phosphorus.

[0063] (Configuration 7) An inductor according to any one of configurations 1 to 6, wherein the low conductivity layer contains, in addition to phosphorus (P), iron (Fe), zinc (Zn), manganese (Mn), and / or oxygen (O). According to the inductor of configuration 7, the withstand voltage of the inductor can be increased by using, as a low conductivity layer, a compound layer of phosphorus and other elements contained in the element, which can be easily formed, for example, by surface treatment of the element using a compound solution containing phosphorus.

[0064] (Configuration 8) A coil conductor forming step of producing a coil conductor having a winding portion around which a conducting wire is wound and a pair of lead portions led out from the winding portion; an element molding step of embedding the coil conductor in an element containing magnetic particles and resin so that the lead portions of the coil conductor are exposed from the surface of the element; a surface treatment step of irradiating laser light onto planned electrode locations on the surface of the element including exposed portions of the lead portions exposed from the element body to remove part of the resin on the surface of the element body at the planned electrode locations; and a plating layer formation step of forming an external electrode by plating at a planned electrode location, wherein in the plating layer formation step, after completion of the surface treatment step, the planned electrode location of the element body is oxidized in an oxygen atmosphere for a predetermined period of time, and then the element body is immersed in an aqueous solution of a phosphorus compound to form a low conductivity layer having a lower conductivity than copper on the surface of the element body at the planned electrode location, and a copper plating layer that constitutes the external electrode is formed on the exposed portion of the lead-out portion and on the low conductivity layer at the planned electrode location. According to the method for manufacturing an inductor of configuration 8, a low conductivity layer can be easily formed between the external electrodes and the surface of the element body, and an inductor with high withstand voltage can be easily manufactured. [Explanation of symbols]

[0065] 1...inductor, 2...element body, 4...external electrode, 5...low conductivity layer, 10...bottom surface, 12...top surface, 14...end surface, 16...side surface, 20...coil conductor, 22...winding portion, 23...middle portion, 24...drawing portion, 30...core, A, A1, A2...electrode extension region.

Claims

1. a coil conductor having a winding portion around which a conducting wire is wound and a pair of lead-out portions led out from the winding portion; an element body containing magnetic particles and a resin and enclosing the coil conductor; an external electrode connected to an exposed portion of the lead portion that is exposed from the surface of the element body; Equipped with a low-conductivity layer having a lower conductivity than the external electrode is provided between the surface of the element body and the external electrode in an area of ​​the surface of the element body where the exposed portion of the lead portion is not present; Inductor.

2. The element body has a pair of opposing end surfaces, the exposed portion of the lead portion is located on the end surface of the element body, the low conductivity layer is formed in a region of the end surface where the exposed portion is not present; 10. The inductor of claim 1.

3. the low conductivity layer is formed on a portion of the end surface where a conductor portion extending into the element body from the exposed portion of the lead-out portion toward the winding portion faces an external electrode.

3. The inductor according to claim 2.

4. the element body has a mounting surface that is orthogonal to the pair of end surfaces, the low conductivity layer is formed on the mounting surface at a position where the winding portion and the external electrode sandwich a part of the element body.

3. The inductor according to claim 2.

5. the external electrodes include copper plating layers, The conductivity of the low conductivity layer is lower than the conductivity of copper.

10. The inductor of claim 1.

6. the low conductivity layer contains phosphorus (P); 6. An inductor according to claim 1.

7. the low conductivity layer contains, in addition to phosphorus (P), iron (Fe), zinc (Zn), manganese (Mn), and / or oxygen (O); 7. The inductor according to claim 6.

8. a coil conductor forming step of fabricating a coil conductor having a winding portion around which a conducting wire is wound and a pair of lead portions led out from the winding portion; an element molding step of embedding the coil conductor in an element containing magnetic particles and a resin so that the lead-out portion of the coil conductor is exposed from a surface of the element; a surface treatment step of irradiating laser light onto planned electrode locations on the surface of the element body, including exposed portions of the lead-out portions that are exposed from the element body, to remove part of the resin on the surface of the element body at the planned electrode locations; a plating layer forming step of forming external electrodes by plating on the electrode-planed locations of the element body including the exposed portions; and In the plating layer forming step, After the surface treatment step is completed, the electrode-planed portions of the element body are oxidized in an oxygen atmosphere for a predetermined time, and then immersing the element body in an aqueous solution of a phosphorus compound to form a low-conductivity layer having a lower conductivity than copper on the surface of the element body in the area intended for the electrode; a copper plating layer constituting the external electrode is formed on the exposed portion of the lead portion and the low conductivity layer at the intended electrode location; How to manufacture an inductor.

Images