inductor

Abstract

The present application provides an inductor. In an inductor composed of a metal plate buried in a magnetic core, the direct current resistance is suppressed to be low, and the size of a solder solidification preventing portion is prevented from increasing at the time of mounting to a circuit substrate. The inductor is provided with a magnetic core containing magnetic powder and a conductor buried in the magnetic core, the magnetic core is provided with a mounting surface toward a mounting substrate side at the time of mounting, a pair of end surfaces orthogonal to the mounting surface, and a pair of side surfaces orthogonal to the mounting surface and the pair of end surfaces, the conductor is provided with a wire portion extending across the pair of end surfaces inside the magnetic core and a pair of electrode portions provided at both sides of the end portion of the wire portion and continuously extending from the end surface of the magnetic core to the mounting surface, the electrode portions are exposed at the side surfaces of the magnetic core, and the edge portion of both sides of the end portion of the wire portion corresponding to the side surfaces of the magnetic core is in a notch shape formed by cutting off the portion inside the magnetic core than the portion connected to the electrode portion.

Description

Technical Field

[0001] This invention relates to inductors. Background Technology

[0002] Patent Document 1 describes an inductor in which solder plating is applied to the end portion of a metal plate extending from a magnetic core, and the end portion is bent to serve as an external terminal.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2019-153642

[0004] For example, in inductors that handle large currents, such as power supply circuits, in order to suppress DC resistance to a low level, external terminals can be formed across the entire width of the magnetic core, so that the two ends (electrode sides) of the external terminals in the width direction are exposed on both sides of the magnetic core.

[0005] However, depending on the shape of the electrode side exposed on the side of the magnetic core, the size of the solder solidification portion formed on the side of the magnetic core becomes larger when mounting the inductor on the circuit board. For example, high-density mounting of the inductor and other electronic components on the circuit board may become difficult. Summary of the Invention

[0006] The purpose of this invention is to achieve a structure for an inductor made of a metal plate embedded in a magnetic core that can suppress DC resistance and prevent the size of the solder solidification portion from increasing during mounting to a circuit board.

[0007] One aspect of the present invention is an inductor comprising a magnetic core containing magnetic powder and a conductor embedded in the magnetic core. The magnetic core includes: a mounting surface facing a mounting substrate during mounting; a pair of end faces orthogonal to the mounting surface; and a pair of side faces orthogonal to the mounting surface and the pair of end faces. The conductor includes: a conductive portion extending across the pair of end faces inside the magnetic core; and a pair of electrode portions located at the ends of the conductive portion on both sides and extending continuously from the end faces of the magnetic core to the mounting surface. The electrode portions are exposed on the side faces of the magnetic core. The edges of the ends of the conductive portions corresponding to the side faces of the magnetic core are notched, and the notched shape is formed by cutting off a portion closer to the inside of the magnetic core than the portion connected to the electrode portion.

[0008] According to the present invention, for an inductor made of a metal plate embedded in a magnetic core, the DC resistance can be suppressed to a low level, and the size of the solder solidification portion can be prevented from increasing when mounted onto a circuit board. Attached Figure Description

[0009] Figure 1 This is a perspective view of the inductor according to an embodiment of the present invention, viewed from the top surface side.

[0010] Figure 2 It is a plan view of the side of the inductor.

[0011] Figure 3 It is a plan view of the end face of the inductor.

[0012] Figure 4 It is a plan view of the mounting surface of the inductor.

[0013] Figure 5 It is a perspective three-dimensional diagram showing the internal structure of an inductor.

[0014] Figure 6 This is a schematic diagram of the manufacturing process of inductor 1.

[0015] Figure 7 It is a plan view of the end face of the inductor.

[0016] Figure 8 It is a plan view of the side of the inductor.

[0017] Figure 9 yes Figure 7 The inductor shown is viewed in section IX-IX.

[0018] Figure 10 yes Figure 8 The inductor shown is viewed in X-X section.

[0019] Figure 11 yes Figure 8 The inductor shown is viewed in section XI-XI.

[0020] Figure 12 This is an example of the shape of the electrode side on the side of an inductor in related technologies.

[0021] Figure 13 Is Figure 12 Examples of the shapes of solder solidification portions formed on the side of electrodes in related technologies are shown.

[0022] Figure 14 From Figure 13 Observe in the direction of the arrow shown Figure 13 The diagram shows the solidified portion of the solder.

[0023] Figure 15 This is a diagram showing the structure of the conductor of the inductor in this embodiment.

[0024] Figure 16 This is a diagram showing an example of a plating extension formed on the mounting surface of a magnetic core.

[0025] Explanation of reference numerals in the attached figures

[0026] 1, 80…Inductor; 2…Blank; 4…External electrode; 10…Mounting surface; 12…Upper surface; 14…End face; 16, 85…Side surface; 20…Conductor; 22…Wire portion; 22A…End; 22A1…Electrode connection portion; 22A2…Edge portion; 24…Electrode portion; 24A…Surface; 26…First electrode portion; 27…Second electrode portion; 30…Magnetic core; 40…First sheet; 42…Second sheet; 50…Nickel plating (Ni plating); 51…Tin plating (Sn plating); 52, 53, 82…Electrode side surface; 80…Inductor; 81…Molded body; 83…Circuit board; 84, 86…Solder solidification portion. Detailed Implementation

[0027] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0028] Figure 1 This is a perspective view of the inductor 1 of this embodiment as seen from the side of the upper surface 12. Figure 2 This is a plan view of the side 16 of inductor 1. Figure 3 This is a plan view of the end face 14 of inductor 1. Figure 4 This is a plan view of the mounting surface 10 of inductor 1.

[0029] The inductor 1 in this embodiment is configured as a surface-mount electronic component, having a generally rectangular blank 2 and a pair of external electrodes 4 disposed on the surface of the blank 2.

[0030] Hereinafter, for blank 2, the surface facing the mounting substrate (not shown) during installation will be defined as mounting surface 10. Figure 4 The surface opposite the mounting surface 10 is called the upper surface 12, the opposite surface orthogonal to the mounting surface 10 is called the end surface 14, and the opposite surface orthogonal to the mounting surface 10 and the pair of end surfaces 14 is called the side surface 16.

[0031] In addition, such as Figure 1 As shown, the distance from the mounting surface 10 to the upper surface 12 is defined as the thickness T of the blank 2, the distance between a pair of side surfaces 16 is defined as the width W of the blank 2, and the distance between a pair of end faces 14 is defined as the length L of the blank 2.

[0032] Figure 5 This is a perspective perspective view showing the internal structure of inductor 1.

[0033] The blank 2 has a conductor 20 and a generally cuboid-shaped magnetic core 30 on which the conductor 20 is embedded, and is configured as a conductor-encased magnetic component in which such conductor 20 is encased in magnetic core 30.

[0034] The magnetic core 30 is a generally rectangular parallelepiped-shaped molded body formed by pressing and heating a mixture of magnetic powder and resin while containing a conductor 20 inside. The surface of the magnetic core 30 has an oxide insulating film that is more oxidized than the interior of the magnetic core 30. Furthermore, in this embodiment, barium sulfate is mixed into the mixture as a lubricant, in addition to the magnetic powder and resin.

[0035] In the mixed powder of this embodiment, the amount of resin is approximately 3.1 wt% relative to the magnetic powder.

[0036] In addition, the magnetic powder of this embodiment contains two types of particles: first magnetic particles with relatively large average particle size and second magnetic particles with relatively small average particle size. During compression molding, the second magnetic particles, as small particles, enter the spaces between the first magnetic particles along with the resin, thereby increasing the filling rate of the magnetic core 30 and improving the magnetic permeability.

[0037] Here, the ratio (weight ratio) of the first magnetic particle to the second magnetic particle is 70:30 to 85:15, preferably 70:30 to 80:20, and in this embodiment it is 75:25.

[0038] In addition, it is preferable that the ratio of the average particle size of the first magnetic particle to that of the second magnetic particle is 5.0 or higher.

[0039] In addition, magnetic powder can also contain particles of three or more particle sizes, including particles with an average particle size between the first magnetic particle and the second magnetic particle.

[0040] In this embodiment, both the first magnetic particle and the second magnetic particle are particles having a metal particle and an insulating film covering the surface of the metal particle. The metal particle uses Fe-Si based amorphous alloy powder, and the insulating film uses zinc phosphate. The metal particle is covered by the insulating film, thereby improving the insulation resistance and withstand voltage.

[0041] In addition, the metal particles in the first magnetic particle can also be Cr-free Fe-C-Si alloy powder, Fe-Ni-Al alloy powder, Fe-Cr-Al alloy powder, Fe-Si-Al alloy powder, Fe-Ni alloy powder, or Fe-Ni-Mo alloy powder.

[0042] In addition, other phosphates (magnesium phosphate, calcium phosphate, manganese phosphate, cadmium phosphate, etc.) or resin materials (silicone resins, epoxy resins, phenolic resins, polyamide resins, polyimide resins, polyphenylene sulfide resins, etc.) can also be used for the insulating film in the first and second magnetic particles.

[0043] In the mixed powder of this embodiment, the resin material used is an epoxy resin mainly composed of bisphenol A type epoxy resin.

[0044] In addition, epoxy resin can also be phenolic varnish-type epoxy resin.

[0045] In addition, the resin material can be any material other than epoxy resin, and it can also be two or more materials. For example, in addition to epoxy resin, thermosetting resins such as phenolic resin, polyester resin, polyimide resin, and polyolefin resin can also be used.

[0046] like Figure 5 As shown, the conductor 20 has a wire portion 22 extending across a pair of end faces 14 inside the magnetic core 30 and an electrode portion 24 integrally formed at both ends of the wire portion 22.

[0047] The surfaces 24A of the electrode portion 24 are exposed from the end face 14 of the magnetic core 30 and the mounting surface 10, respectively. To ensure mountability, the surfaces 24A are sequentially plated with nickel (Ni) and tin (Sn) to form the external electrode 4. Then, the external electrode 4 formed on the mounting surface 10 is electrically connected to the wiring of the circuit board using a suitable mounting method such as solder.

[0048] In this embodiment, such as Figures 1-5 As shown, the electrode portion 24 of the conductor 20 is configured such that only the surface 24A is exposed on the mounting surface 10 and the end face 14, thus suppressing the amount of protrusion from the magnetic core 30. Therefore, since the protrusion of the electrode portion 24 is almost negligible, the magnetic core 30 can be increased to the same size as the specified dimensions of the inductor 1, enabling a small, thin, and high-performance inductor 1.

[0049] If the length of the conductor portion 22 in the direction of the width W of the magnetic core 30 is defined as the conductor portion width WA, and the length of the electrode portion 24 is defined as the electrode width WB, then as Figure 5 As shown, in this embodiment, the electrode width WB of the electrode portion 24 is wider than the wire portion width WA, thereby achieving low DC resistance.

[0050] Such an electrode portion 24 is formed in an approximately L-shaped manner in the LT cross-section of the LT surface along each direction containing the length L and thickness T of the magnetic core 30.

[0051] In detail, the electrode portion 24 has a first electrode portion 26 that is bent and extends substantially vertically at the end 22A of the conductor portion 22, and a second electrode portion 27 that is bent and extends substantially vertically at the lower end 26A of the first electrode portion 26. These first electrode portions 26 and second electrode portions 27 are configured in an L-shape. Furthermore, the surfaces 24A of these first electrode portions 26 and second electrode portions 27 are exposed from the end face 14 of the magnetic core 30 and the mounting surface 10, forming the external electrode 4.

[0052] According to the electrode section 24, compared with the case where the wire section 22 and the electrode section 24 (external electrode 4) are separately and independently constructed, since there is no joint surface in the low resistance region where the main current flows in the external electrode 4, that is, between the wire section 22 and the electrode section 24 (external electrode 4), the resistance value can be suppressed and a larger current can flow.

[0053] Furthermore, the conductor 20 in this embodiment is made of tough copper, which allows for the flow of a larger current.

[0054] Based on the above structure, the inductor 1 of this embodiment can achieve an inductance of about 10nH or more, a DC resistance of about 0.85mΩ or less, a rated current of 15A or more when the temperature rises (wherein, when the temperature rises by 40 degrees), and a DC superimposed current of 15A or more (wherein, the frequency is 1MHz) with dimensions of about 2.5mm in length, about 2.0mm in width, and about 1.0mm in thickness.

[0055] Such an inductor 1 is used as an impedance matching coil (matching coil) in power supply circuits of DC-DC converters with charge pump mode that boosts voltage through capacitors and switches, as well as LC filters, and can be used in electronic devices such as personal computers, DVD players, digital cameras, TVs, mobile phones, smartphones, automotive electronics, and medical / industrial equipment. However, the application of inductor 1 is not limited to this; for example, it can also be used in tuning circuits, filtering circuits, and rectifier smoothing circuits.

[0056] Furthermore, in inductor 1, a preform protective layer may be formed on the entire surface of the preform 2, excluding the area of ​​the external electrode 4. The material for the preform protective layer can be, for example, a thermosetting resin such as epoxy resin, polyimide resin, or phenolic resin, or a thermoplastic resin such as polyethylene resin or polyamide resin. In addition, these resins may also contain fillers such as silicon dioxide or titanium dioxide.

[0057] Figure 6 This is a schematic diagram of the manufacturing process of inductor 1.

[0058] As shown in the figure, the manufacturing process of inductor 1 includes: conductor component forming process, blank sheet forming process, first sheet insertion process, second sheet arrangement process, thermoforming / curing process, tumbling process, pretreatment process, and plating process.

[0059] The conductor component forming process is the process of forming the aforementioned conductor 20.

[0060] In this embodiment, firstly, a copper sheet of a predetermined shape is formed by stamping a copper plate of a predetermined thickness. Next, the conductor 20 is formed by bending the copper sheet. At this time, the first electrode portion 26 and the second electrode portion 27 of the electrode portion 24 are also bent. That is, the conductor 20 is formed through this conductor component forming process. The conductor 20 integrally has the aforementioned wire portion 22 and electrode portion 24, and before being embedded in the magnetic core 30, the first electrode portion 26 and the second electrode portion 27 of the electrode portion 24 are also pre-formed (i.e., pre-formed).

[0061] The sheet forming process is the process of forming the first sheet 40 and the second sheet 42 into two pre-formed bodies.

[0062] The pre-formed body is a structure formed by pressing the above-mentioned mixed powder, which serves as the blank 2, into a solid shape that is easy to handle. The first sheet 40 and the second sheet 42 are pre-formed bodies disposed on the lower and upper sides of the conductor portion 22 of the conductor 20, respectively, and are both formed into a generally plate-like shape.

[0063] The first sheet insertion step is a process in which, after the conductor 20 is placed in the molding die, a first sheet 40 is inserted into the space between the conductor 20 and the pair of electrode portions 24, below the conductor portion 22. More specifically, the conductor 20 has L-shaped electrode portions 24 in an L-section in a generally C-shaped LT section, located at the ends 22A on both sides of the conductor portion 22, and the first sheet 40 is inserted into the space surrounded by these conductor portions 22 and the pair of electrode portions 24.

[0064] The second sheet placement process is the process of placing the second sheet 42 on the conductor portion 22 of the conductor 20.

[0065] The thermoforming / curing process involves heating the first sheet 40 and the second sheet 42 disposed in the molding die, and applying pressure in the overlapping direction of the first sheet 40 and the second sheet 42 to cure them, thereby integrating the first sheet 40, the conductor 20, and the second sheet 42. This results in the formation of a molded body containing the conductor 20.

[0066] As described above, since the first sheet 40 is molded within the space surrounded by the conductor portion 22 and the pair of electrode portions 24, a molded body is obtained in which the conductor portion 22 is embedded in the molded body, and the surfaces of the electrode portions 24, including the first electrode portion 26 and the second electrode portion 27, are exposed approximately coplanar with the magnetic core 30. Furthermore, since the first electrode portion 26 and the second electrode portion 27 of the electrode portion 24 are formed through the aforementioned conductor component molding process, no further processing is required to form these first electrode portions 26 and second electrode portions 27 on the molded body.

[0067] The tumbling process is the process of tumbling the molded body, through which the corners of the molded body are rounded.

[0068] In the pretreatment process, as a surface treatment of the molded body for the subsequent plating process, heat treatment and cleaning are performed. In the plating process, nickel (Ni) and tin (Sn) are sequentially plated onto the surface 24A of the electrode portion 24 by barrel plating.

[0069] [Location where the coating is formed]

[0070] In the inductor 1 of this embodiment, in the conductor component forming process, the conductor 20 is formed by bending a conductive plate that has not been plated. Then, in a subsequent process, the conductor 20 is embedded in the magnetic core 30 so that the surface 24A of the electrode portion 24 of the conductor 20 is exposed from the magnetic core 30. Then, in the plating process, the exposed surface 24A is plated.

[0071] Therefore, defects such as cracking and peeling of the plating layer caused by bending the conductive plate after plating is formed, as in the past, are prevented from occurring in the electrode section 24.

[0072] Furthermore, in the inductor 1 of this embodiment, in order to suppress the DC resistance of the conductor 20 to a low level, the electrode width WB of the first electrode portion 26 and the second electrode portion 27 is the same as the width W of the magnetic core 30, and the inductor 1 is configured such that the sides of the first electrode portion 26 and the second electrode portion 27 protrude from the magnetic core 30. Hereinafter, the side of the electrode portion 24 will also be referred to as the electrode side.

[0073] Then, in the plating process, a plating layer is formed on the entire portion of the conductor 20 exposed from the magnetic core 30, including surface 24A, by barrel plating. Therefore, in Figure 5 In the process, a coating is also formed on the electrode sides of the first electrode portion 26 and the second electrode portion 27 exposed from the side 16 of the magnetic core 30.

[0074] As a result, in this embodiment, no masking process is used during plating, so the manufacturing process is not complicated. A good plating layer without cracks, peeling, etc. can be formed on the entire part of the electrode portion 24 exposed from the magnetic core 30, thereby achieving a good mounting state of the inductor 1 to the circuit board, etc.

[0075] Furthermore, since the surface of the electrode portion 24 opposite to the surface 24A is embedded inside the magnetic core 30, which is a molded body, solder can be prevented from entering between the electrode portion 24 and the magnetic core 30 when the inductor 1 is mounted to a circuit board or the like. Therefore, the inductor 1 can prevent the reduction in reliability and deterioration of electrical characteristics caused by the entry of the aforementioned solder when mounted to a circuit board or the like.

[0076] in addition, Figure 6 The conductor component forming process shown is equivalent to the process of forming conductor 20 by bending a conductive plate. Furthermore, Figure 6 The first sheet insertion step, the second sheet placement step, and the thermoforming / curing step shown correspond to the steps of embedding the conductor 20 within the magnetic core 30 so that a portion of the conductor 20 is exposed from the magnetic core 30. Furthermore, Figure 6 The plating process shown is equivalent to the process of plating the surface portion of conductor 20 exposed from magnetic core 30.

[0077] Figure 7 and Figure 3 The same applies to the plan view of end face 14 of inductor 1. Figure 8 and Figure 2 The same applies to the plan view of side 16 of inductor 1. Furthermore, Figure 9 yes Figure 7 IX-IX section view, Figure 10 yes Figure 8 The X-X section view, Figure 11 yes Figure 8 The XI-XI section view.

[0078] exist Figure 9 , Figure 10 as well as Figure 11 In the conductor 20, a Ni plating layer 50 and a Sn plating layer 51 are formed on the portions of the first electrode portion 26 and the second electrode portion 27 exposed from the magnetic core 30 (including the surface 24A). Furthermore, the surfaces of the first electrode portion 26 and the second electrode portion 27 facing the surfaces exposed from the magnetic core 30, including the surface 24A, are embedded within the magnetic core 30 and are not coated.

[0079] As described above, in the inductor 1 of this embodiment, in Figure 10 The electrode side 52 of the second electrode portion 27 exposed from the magnetic core 30, and in Figure 11A Ni plating layer 50 and a Sn plating layer 51 are also formed on the electrode side 53 of the first electrode portion 26 exposed from the magnetic core 30.

[0080] [The shape of the electrode side exposed on the side of the magnetic core]

[0081] As described above, in the inductor 1, plating is formed on the electrode sides of the first electrode portion 26 and the second electrode portion 27 exposed from the side surface 16 of the magnetic core 30. Therefore, when the inductor 1 is mounted on a circuit board or the like using solder, the solder rises to the electrode sides where solder wettability is good, thus improving the fixing strength of the inductor 1 relative to the circuit board or the like compared to the case where the electrode sides are not exposed from the magnetic core 30.

[0082] However, depending on the shape of the electrode side exposed on the side 16 of the magnetic core 30, the size of the solder solidification portion formed on the side 16 of the magnetic core 30 becomes larger, which may make it difficult to mount the inductor 1 and other electronic components on the circuit board at high density.

[0083] Figure 12 This is an example of the shape of the electrode side on the side of the molded body of the inductor, which is a related technology of this embodiment. Figure 13 It is Figure 12 The inductor 80 shown is formed when it is mounted on the circuit board 83. Figure 12 The illustration shows an example of the shape of the solder solidification portion on the electrode side 82 on the left. Furthermore, Figure 14 From Figure 13 Observe the direction of the arrow in the diagram. Figure 13 The diagram shows the solidified portion of the solder.

[0084] exist Figure 12 In the example shown, the electrode side 82 protrudes from the side of the molded body 81 of the inductor 80 in a roughly C-shape. For example... Figure 13 As shown, when such an inductor 80 is mounted on a circuit board 83, the solder solidification portion 84 may be formed to cover the surface of the molded body 81, which is surrounded by the electrode side surface 82 and is in a generally C-shape. This solder solidification portion 84 is formed in a block shape so that it bridges the portions of the electrode side surface 82 across the surface of the molded body 81 where solder wettability is poor (e.g., between the upper and lower portions of the generally C-shape shown in the illustration). Therefore, as... Figure 14 As shown, the protrusion distance d10 of the solder solidification portion 84 protruding from the side 85 of the molded body 81 is longer than the protrusion distance d12 of the solder solidification portion 86 (shown by a single-dotted line in the illustration, the so-called solder fillet) without such a bridging. As a result, Figure 12 The inductor 80 shown in the related technology is difficult to mount at high density with other electronic components on the circuit board.

[0085] Therefore, in order to achieve high-density mounting on the circuit board, the inductor 1 of the embodiment of the present invention is configured such that only the electrode sides of the first electrode portion 26 and the second electrode portion 27 are exposed in a generally L-shape on the side 16 of the magnetic core 30, and the electrode sides of the wire portion 22 are not exposed on the side 16 of the magnetic core 30.

[0086] Specifically, the edge portion of the ends of both sides of the conductor portion 22 corresponding to the side surface 16 of the magnetic core 30 is notched, and this notched shape is formed by cutting off the portion of the part connected to the electrode portion 24 that is closer to the inside of the magnetic core 30.

[0087] Figure 15 This is a diagram showing the structure of conductor 20. Figure 15 The image above is a plan view of the conductor 20 as seen from the side of the upper surface 12 of the inductor 1. Figure 15 The following figure is a side view of conductor 20, viewed from the side 16 of inductor 1. Figure 15 In the figure above, the conductor portion 22 is formed in a shape where the ends 22A on both sides of the electrode portion 24 extend along the width W of the inductor 1 (approximately H-shaped when viewed from the top surface 12). The width of the electrode connection portion 22A1 in this end portion 22A that is connected to the electrode portion 24 is wider than the width WA of the conductor portion, and is the same as the electrode width WB of the electrode portion 24. As a result, the conductor 20 achieves a further reduction in DC resistance.

[0088] Here, since the electrode width WB is the same as the width W of the magnetic core 30, the electrode portion 24 is exposed on a pair of side surfaces 16 of the magnetic core 30. On the other hand, for the wire portion 22, although the width of the electrode connection portion 22A1 at the end 22A is the electrode width WA, the two sides of the end 22A in the direction of the width W of the magnetic core 30 are chamfered and cut off by C, and are not exposed on a pair of side surfaces 16 of the magnetic core 30.

[0089] Specifically, at the end 22A of the conductor portion 22, the edge portion 22A2 located in the direction of the width W of the magnetic core 30, although located on the side 16 of the magnetic core 30, is formed into a notch shape by a C-bevel. This notch shape is formed by cutting off the portion closer to the inside of the magnetic core 30 than the electrode connection portion 22A1. In this way, by forming the edge portion 22A2 of the end 22A into a notch shape, even if the width of the electrode connection portion 22A1 in the end 22A is equal to the electrode width WB of the electrode portion 24, only the electrode portion 24 is exposed on the side 16 of the magnetic core 30, while the conductor portion 22 is not exposed. Therefore, on the side 16 of the magnetic core 30, the shape of the conductor 20 will not become... Figure 12 Instead of the C-shape shown, it is in the shape of... Figure 2As shown, it has a roughly L-shaped form. Therefore, the conductor 20 exposed on the side 16 of the magnetic core 30 will not form a shape like... Figure 13 and Figure 14 The blocky solder solidification section 84 that spans the surface of the magnetic core 30, as shown, allows the inductor 1 to be mounted on the circuit board with high density along with other electronic components.

[0090] Furthermore, the method of forming the edge portion 22A2 of the end 22A into a notch shape is not limited to chamfering. For example, in the conductor component forming process described above, during stamping, the copper plate can also be stamped in a shape that includes the notch shape of the edge portion 22A2 of the end 22A.

[0091] [Prevent unnecessary plating]

[0092] As described above, in this embodiment, the electrode portion 24 is plated by barrel plating during the plating process. Therefore, as... Figure 9 , Figure 10 as well as Figure 11 As shown, a plating layer is formed on the entire portion of the electrode section 24 (first electrode section 26 and second electrode section 27) that is exposed from the magnetic core 30, which enables good mounting of the inductor 1 to the circuit board and the like.

[0093] However, on the other hand, during barrel plating, since the entire blank 2, including the magnetic core 30 and the conductor 20, is immersed in the barrel plating electrolyte, the surface of the magnetic core 30 becomes locally charged depending on the surface condition of the magnetic core 30. This may cause the plating layer, which should only be formed within the range of the electrode portion 24, to unexpectedly extend beyond the range of the electrode portion 24 toward the surface of the magnetic core 30 (plating extension).

[0094] Figure 16 This is a diagram illustrating an example of a plating extension formed on the mounting surface 10 of the magnetic core 30. In the example shown, dotted plating portions (white dots scattered on the surface of the magnetic core 30) are formed, extending from the edge of the second electrode portion 27 of the electrode portion 24 toward the surface of the magnetic core 30, with the most dotted plating in the area enclosed by ellipse A.

[0095] The inventors of this invention conducted an in-depth study on the relationship between various surface treatment conditions (heating temperature and holding time) of the blank 2 and the frequency of plating extension, and discovered that heating the blank 2 in an atmospheric atmosphere as a pretreatment for plating changes the surface state of the magnetic core 30, thereby effectively preventing plating extension.

[0096] Therefore, in this embodiment, as described above, the pretreatment process for the plating process includes a heating process to heat the tumbled magnetic core 30 to perform surface treatment of the magnetic core 30 and a cleaning process to etch and clean the surface of the heated electrode portion 24.

[0097] Table 1 below shows the relationship between the heat treatment conditions of the billet 2 under atmospheric conditions during the heating process and the occurrence rate of plating extension during subsequent barrel plating. The first row (top row) of Table 1 is the sample number, the second row is the heating temperature during the heat treatment, the third row is the holding time of the heating temperature, and the fourth row is the probability of plating extension during subsequent barrel plating. The total number of samples for each sample number is 500, and the probability of plating extension is the ratio of the number of samples with plating extension in each sample number to the total number of samples. Regarding whether plating extension occurs, a case where the plating extends more than 30% of the electrode width WB in the L direction is considered to have plating extension. In addition, the heating temperature shown in Table 1 is the furnace atmosphere temperature in the oven used to heat the samples.

[0098] According to Table 1, the heat treatment conditions required to prevent plating extension are a heating temperature of at least 200°C and a holding time of at least 30 minutes. Taking into account manufacturing deviations, it is preferable to include a holding time of approximately 10 minutes, with heat treatment conditions of 200°C or higher and a holding time of at least 40 minutes. This effect of preventing plating extension through heat treatment is considered to be due to the oxidation of the surface of the magnetic particles exposed on the surface of the magnetic core 30 during barrel plating (electroplating) by heating in the atmosphere, forming an oxide insulating film. That is, it can be considered that by forming an oxide insulating film on the surface of the magnetic particles exposed on the surface of the magnetic core 30 as described above, the entire surface of the magnetic core 30 has good electrical insulation, resulting in the prevention of plating metal precipitation onto the surface of the magnetic core 30 during barrel plating (electroplating), thus preventing plating extension.

[0099] Table 1

[0100]

[0101] Furthermore, during the heat treatment, the surface of the conductor 20 exposed from the magnetic core 30 is also oxidized due to the overall heating of the blank 2. Therefore, in this embodiment, as a pretreatment, the blank 2 is cleaned after the heat treatment. In the cleaning process, the oxide film on the surface of the conductor 20 exposed from the magnetic core 30 is removed by immersing the molded body in a liquid that dissolves only the components of the conductor 20 (i.e., by performing wet etching).

[0102] As described above, the inductor 1 of the above embodiment includes a magnetic core 30 containing magnetic powder and a conductor 20 embedded in the magnetic core 30. The magnetic core 30 includes: a mounting surface 10 facing the mounting substrate side during mounting, a pair of end faces 14 orthogonal to the mounting surface 10, and a pair of side faces 16 orthogonal to the mounting surface 10 and the pair of end faces 14. Furthermore, the conductor 20 includes: a wire portion 22 extending across the pair of end faces 14 inside the magnetic core 30, and a pair of electrode portions 24 provided on both sides of the wire portion 22 and extending continuously from the end faces 14 of the magnetic core 30 to the mounting surface 10. Moreover, the electrode portions 24 are exposed on the side faces 16 of the magnetic core 30, and the edge portions of the ends of the wire portions 22 corresponding to the side faces 16 of the magnetic core 30 are notched, which are formed by cutting off the portion closer to the inside of the magnetic core 30 than the portion connected to the electrode portion 24.

[0103] According to this structure, for an inductor 1 composed of conductors 20 embedded in the magnetic core 30, the DC resistance can be suppressed to a low level, and the size of the solder solidification portion can be prevented from increasing when it is mounted on the circuit board.

[0104] Furthermore, a nickel (Ni) plating and a tin (Sn) plating are formed on the surface of the electrode portion 24 at the portion exposed from the side surface 16 of the magnetic core 30. According to this structure, a tin plating 51 with good solder wettability can be formed on the side surfaces of the first electrode portion 26 and the second electrode portion 27 with practically sufficient strength.

[0105] The manufacturing method described above is a method for manufacturing an inductor 1. The inductor 1 includes a magnetic core 30 made of magnetic powder and resin and a conductor 20 embedded in the magnetic core 30. The method includes: a step of forming the conductor 20 by bending a conductive plate; a step of embedding the conductor 20 in the magnetic core 30 so that a portion of the conductor 20 is exposed from the magnetic core 30; and a step of plating the exposed surface portion of the conductor 20 from the magnetic core 30.

[0106] According to this structure, since the portion of the conductor 20 exposed from the magnetic core 30 after pre-bending is plated, the manufacturing process is not complicated by masking or other processes during plating. This prevents defects such as cracking and peeling of the plating caused by bending the conductive plate after plating, as was common in the past. Therefore, the inductor 1 can prevent solder joint defects caused by plating defects in the conductor 20, achieving a good mounting condition for circuit boards and the like.

[0107] Furthermore, in the process of embedding the conductor 20 into the magnetic core 30, the conductor 20 is embedded in the magnetic core 30 such that the side surface of the electrode portion 24, which is part of the conductor 20, is exposed from the magnetic core 30. According to this structure, since a plating layer is also formed on the side surface of the electrode portion 24 exposed from the magnetic core 30 (electrode side surface), the solder wettability of the side surface of the electrode portion 24 can be improved, characteristic degradation during mounting of the inductor 1 to a circuit board or the like can be suppressed, and a good mounting condition can be achieved.

[0108] Furthermore, the magnetic core 30 includes: a mounting surface 10 facing the mounting substrate side during installation, a pair of end faces 14 orthogonal to the mounting surface 10, and a pair of side faces 16 orthogonal to the mounting surface 10 and the pair of end faces 14. The conductor 20 includes: a wire portion 22 extending across the pair of end faces 14 inside the magnetic core 30 when embedded in it, and a pair of electrode portions 24 extending from the end faces 14 of the magnetic core 30 to the mounting surface 10. In the process of embedding the conductor 20 into the magnetic core 30, the conductor 20 is embedded in the magnetic core 30 such that one surface 24A of the electrode portion 24 is exposed from the mounting surface 10, the other surfaces opposite to this one surface are embedded in the magnetic core 30, and the side faces (electrode side faces) of the electrode portion 24 are exposed from the side faces of the magnetic core 30.

[0109] According to this structure, since a plating layer is also formed on the side of the electrode portion 24 exposed from the magnetic core 30 (electrode side), the solder wettability of the electrode side of the electrode portion 24 can be improved, achieving a good mounting condition when mounting the inductor 1 to a circuit board or the like. Furthermore, since the back side of the electrode portion 24 opposite to surface 24A is embedded inside the magnetic core 30, no gap is generated between the back side of the electrode portion 24 and the magnetic core 30. This prevents solder from spreading into the aforementioned gap when the inductor 1 is mounted on the circuit board, preventing degradation of the inductor 1's characteristics during mounting.

[0110] Furthermore, the manufacturing method of inductor 1 includes a step of tumbling the magnetic core 30 on which the conductor 20 is embedded, and the aforementioned plating step is performed after the tumbling step. According to this structure, since the portion of the conductor 20 exposed from the magnetic core 30 is plating after the magnetic core 30 has been tumbled to approximately the final product shape, it is possible to prevent other portions of the conductor 20 from re-exposing from the magnetic core 30 after plating. As a result, it is possible to avoid the formation of unplated portions of the conductor 20 exposed from the magnetic core 30, achieving a good mounting condition of inductor 1 on the circuit board.

[0111] Furthermore, the plating process includes a step of plating nickel (Ni) on the portion of the conductor 20 exposed from the magnetic core 30 and a step of plating tin (Sn) on the nickel plating layer. This structure improves the bonding strength between the tin plating layer, which has good solder wettability, and the conductor 20.

[0112] Furthermore, the inductor 1 in the above embodiment is an inductor comprising a magnetic core 30 containing magnetic powder and a conductor 20 embedded within the magnetic core 30. The magnetic core 30 includes: a mounting surface 10 facing the mounting substrate side during mounting, a pair of end faces 14 orthogonal to the mounting surface 10, and a pair of side faces 16 orthogonal to the mounting surface 10 and the pair of end faces 14. The conductor 20 includes: a wire portion 22 extending across the pair of end faces 14 inside the magnetic core 30, and a pair of electrode portions 24 extending continuously from the end faces 14 of the magnetic core 30 to the mounting surface 10. Furthermore, the side faces of the electrode portions 24 are exposed from the side faces 16 of the magnetic core 30, and a plating layer is formed on the exposed side faces of the electrode portions 24.

[0113] According to this structure, since a plating layer is also formed on the electrode side of the electrode portion 24, a good mounting state of the inductor 1 on the circuit board can be achieved.

[0114] The manufacturing method described above is a method for manufacturing inductor 1. Inductor 1 includes a magnetic core 30 made of magnetic powder and resin and a conductor 20 embedded within the magnetic core 30. The method includes a step of embedding the conductor 20 within the magnetic core 30 such that a portion of the conductor 20 is exposed from the magnetic core 30. Furthermore, this manufacturing method includes a step of performing a pre-plating treatment by heat treatment of the magnetic core 30 at a temperature of 200°C or higher for at least 40 minutes in an atmospheric atmosphere, and a step of plating the portion of the conductor 20 exposed from the magnetic core 30 after the pre-plating treatment.

[0115] According to this structure, the manufacturing process is not complicated, and unwanted plating is effectively prevented from forming on the surface of the magnetic core 30, thus preventing the inductor 1 from deteriorating along with the formation of such plating.

[0116] Furthermore, in the plating process, nickel plating is performed on the portion of the conductor 20 exposed from the magnetic core 30 by barrel plating, followed by tin plating. Based on this structure, without masking or other processes, a tin plating layer with good solder wettability can be formed on the portion of the conductor 20 exposed from the magnetic core 30 with practically sufficient strength.

[0117] Furthermore, the manufacturing method includes a step of tumbling the magnetic core 30 on which the conductor 20 is embedded. The pre-plating treatment step is performed after the aforementioned tumbling step. According to this structure, by tumbling, magnetic particles are exposed from the surface of the magnetic core 30. Even if an undesirable plating layer is easily formed on this surface, the formation of such an undesirable plating layer can be effectively prevented, and the characteristics of the inductor 1 associated with the formation of such a plating layer can be prevented from deteriorating.

[0118] In addition, the pretreatment process for plating described above includes a cleaning process, which involves etching the surface of the portion of the conductor 20 exposed from the magnetic core 30 after the heat treatment. According to this structure, unwanted oxide films formed on the exposed surface of the conductor 20 due to the heat treatment are removed, and a good plating layer can be formed on the exposed surface.

[0119] In the above embodiment, the electrode portion 24 is formed by bending a conductive plate, but the effect of the above-described pre-plating treatment is not limited to the case of electrodes (terminals) formed by bending such a conductive plate. The above-described pre-plating treatment can prevent the formation of undesirable plating layers on the surface of the magnetic core for inductors that plate metal portions of arbitrary shapes exposed from the magnetic core to become terminals.

[0120] (Postscript 1)

[0121] A method for manufacturing an inductor, the inductor comprising a magnetic core made of magnetic powder and resin and a conductor embedded in the magnetic core, the method comprising: a step of forming the conductor by bending a conductive plate; a step of embedding the conductor in the magnetic core such that a portion of the conductor is exposed from the magnetic core; and a step of plating the exposed surface portion of the conductor from the magnetic core.

[0122] (Postscript 2)

[0123] A method for manufacturing an inductor, wherein in the above-mentioned embedding process, the conductor is embedded in the magnetic core such that the side of the electrode portion, which is part of the conductor, is exposed from the magnetic core.

[0124] (Note 3)

[0125] A method for manufacturing an inductor, wherein the magnetic core comprises: a mounting surface facing a mounting substrate side during mounting, a pair of end faces orthogonal to the mounting surface, and a pair of side faces orthogonal to the mounting surface and the pair of end faces; the conductor comprises a wire portion extending across the pair of end faces inside the magnetic core when embedded in the magnetic core, and a pair of electrode portions extending continuously from the end faces of the magnetic core to the mounting surface; in the embedding process, the conductor is embedded in the magnetic core such that one side of the electrode portion is exposed from the mounting surface, the other side facing that side is embedded in the magnetic core, and the side face of the electrode portion is exposed from the side face of the magnetic core.

[0126] (Note 4)

[0127] A method for manufacturing an inductor further includes a step of tumbling the magnetic core on which the conductor is embedded, wherein the plating step is performed after the tumbling step.

[0128] (Note 5)

[0129] A method for manufacturing an inductor, wherein the plating process comprises: a process of plating nickel (Ni plating) on ​​the portion of the conductor exposed from the magnetic core, and a process of plating tin (Sn plating) on ​​the nickel plating layer.

[0130] (Note 6)

[0131] An inductor includes a magnetic core containing magnetic powder and a conductor embedded in the magnetic core. The magnetic core includes a mounting surface facing a mounting substrate, a pair of end faces orthogonal to the mounting surface, and a pair of side faces orthogonal to the mounting surface and the pair of end faces. The conductor includes a wire portion extending across the pair of end faces inside the magnetic core, and a pair of electrode portions extending from the end faces of the magnetic core to the mounting surface. The side faces of the electrode portions are exposed from the side faces of the magnetic core, and a plating layer is formed on the exposed side faces of the electrode portions.

[0132] (Note 7)

[0133] A method for manufacturing an inductor, the inductor comprising a magnetic core made of magnetic powder and resin and a conductor embedded in the magnetic core, the method comprising: a step of embedding the conductor in the magnetic core such that a portion of the conductor is exposed from the magnetic core; a step of performing a pre-plating treatment by heat treatment of the magnetic core at a temperature of 200°C or higher for 40 minutes or more in an atmospheric atmosphere; and a step of plating the portion of the conductor exposed from the magnetic core after the pre-plating treatment.

[0134] (Postscript 8)

[0135] A method for manufacturing an inductor, in the above-mentioned plating process, involves plating nickel (Ni) onto the portion of the conductor exposed from the magnetic core by barrel plating, followed by tin (Sn) plating.

[0136] (Note 9)

[0137] A method for manufacturing an inductor further includes a step of tumbling the magnetic core on which the conductor is embedded, wherein the step of performing the pre-plating treatment is performed after the tumbling step.

[0138] (Postscript 10)

[0139] A method for manufacturing an inductor further includes a pre-plating treatment step that involves etching the surface of the conductor exposed from the magnetic core after the heat treatment.

[0140] Furthermore, the above-described embodiments are merely examples of one aspect of the present invention, and can be arbitrarily modified and applied without departing from the spirit of the present invention.

[0141] Furthermore, for the horizontal and vertical directions, as well as various values, shapes, and materials in the above embodiments, unless otherwise specified, there is a range that has the same effect as these directions, values, shapes, and materials (the so-called equivalent range).

Claims

1. An inductor comprising a magnetic core containing magnetic powder and a conductor embedded in the magnetic core, characterized in that, The above-mentioned magnetic core has the following features: The mounting surface faces the mounting substrate side during installation; A pair of end faces, orthogonal to the aforementioned mounting surface; and A pair of side faces, orthogonal to the aforementioned mounting surface and the aforementioned pair of end faces. The above-mentioned conductor has the following characteristics: The conductive portion extends transversely across the pair of end faces within the aforementioned magnetic core; and A pair of electrode portions are disposed at the ends of the aforementioned conductive portion on both sides, and extend continuously from the aforementioned end face of the aforementioned magnetic core to the aforementioned mounting surface. The aforementioned electrode portion is exposed on the aforementioned side of the aforementioned magnetic core. The edges at both ends of the aforementioned conductor portion, corresponding to the two aforementioned side surfaces of the magnetic core, are notched. This notched shape is formed by cutting off a portion of the magnetic core that is closer to the inside of the magnetic core than the portion connected to the aforementioned electrode portion. The width of the electrode connection portion connected to the electrode portion at the end is wider than the width of the wire portion and equal to the electrode width of the electrode portion. The wire portion is not exposed on the side of the magnetic core.

2. The inductor according to claim 1, characterized in that, A nickel (Ni) plating layer and a tin (Sn) plating layer are formed on the surface of the electrode portion at the portion exposed from the side of the magnetic core.

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