Inductors

Abstract

The present invention provides an inductor capable of reducing direct current resistance. The inductor comprises: a body having a magnetic portion including magnetic powder and a first resin; a coil having a winding portion formed by winding a conductor and a pair of lead portions led out from the winding portion, and the coil is enclosed in the body; and a pair of external electrodes connected to at least the terminal ends of the lead portions on the surface of the body. The external electrodes include a conductive resin layer and a first covering layer arranged on the conductive resin layer. The conductive resin layer includes conductive powder and a second resin, and the conductive resin layer includes a plurality of conductive metal portions made of the same material as the first covering layer.

Description

Technical Field

[0001] The present invention relates to inductors. Background Art

[0002] Patent Document 1 proposes an inductor in which an air-core coil is embedded in a magnetic body composed of resin and metal magnetic particles, and terminal electrodes are electrically connected to both ends of the coil and are formed of a conductive resin containing silver (Ag) particles.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2016-32050

[0004] In an external electrode made of a conductive resin containing conductive particles, unlike an external electrode made of plated or sintered metal, the conductivity is ensured by the conductive particles being close to and in contact with each other, so the DC resistance of the external electrode itself is high. Therefore, in an inductor using an external electrode made of a conductive resin, the DC resistance may be high. Summary of the invention

[0005] An object of the present invention is to provide an inductor capable of reducing direct current resistance.

[0006] The inductor according to the first embodiment comprises: a body including a magnetic part including magnetic powder and a first resin; a coil including a winding part including a conductor and a pair of lead parts extending from the winding part, and the coil is enclosed in the body; and a pair of external electrodes connected to at least the terminal parts of the lead parts on the surface of the body. The external electrodes are configured to include a conductive resin layer and a first covering layer arranged on the conductive resin layer. The conductive resin layer includes conductive powder and a second resin, and includes a plurality of conductive metal parts made of the same material as the first covering layer.

[0007] According to one aspect of the present invention, it is possible to provide an inductor capable of reducing direct current resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is a partially transparent perspective view of the inductor of Example 1 as viewed from the upper surface side.

[0009] Figure 2 The inductor of Example 1 is Figure 1 Cross-sectional view at line a-a.

[0010] Figure 3 The inductor of Example 1 is Figure 2 A partial enlarged cross-sectional view of part A.

[0011] Figure 4 is a cross-sectional view of the inductor of Example 2.

[0012] Figure 5 The inductor of Example 2 is Figure 4 A partial enlarged cross-sectional view of part B.

[0013] Figure 6 is a cross-sectional view of an inductor according to Example 3.

[0014] Description of reference numerals: 100, 110, 120...inductor, 10...body, 30...coil, 40...external electrode. DETAILED DESCRIPTION

[0015] The inductor comprises: a body having a magnetic portion including magnetic powder and a first resin; a coil having a winding portion formed by winding a conductor and a pair of lead portions led out from the winding portion, and the coil is enclosed in the body; and a pair of external electrodes connected to at least the terminal ends of the lead portions on the surface of the body. The external electrodes are configured to include a conductive resin layer and a first covering layer arranged on the conductive resin layer. The conductive resin layer is configured to include conductive powder and a second resin, and the conductive resin layer includes a plurality of conductive metal portions made of the same material as the first covering layer.

[0016] By disposing the conductive metal portion in the conductive resin layer, the contact between the conductive powder in the conductive resin layer increases, and the connection resistance between the lead portion of the coil and the external electrode is further reduced.

[0017] Alternatively, the conductive metal portion directly connects the terminal end of the lead portion to the first covering layer. By directly connecting the terminal end of the lead portion to the first covering layer using the conductive metal portion provided on the conductive resin layer, the connection resistance between the lead portion of the coil and the external electrode is further reduced, and the bonding strength of the external electrode to the blank is also improved.

[0018] Alternatively, the surface of the green body on which the external electrode is disposed may have a magnetic powder exposed portion where the magnetic powder is exposed, and at least a portion of the exposed magnetic powder is connected to the first covering layer by a conductive metal portion. By directly connecting the green body and the first covering layer using the conductive metal portion provided on the conductive resin layer, the bonding strength between the green body and the external electrode is improved.

[0019] The conductive metal portion may be arranged in a branch shape. By forming the conductive metal portion in a branch shape, the conductive metal portion that directly connects the lead portion of the coil to the external electrode can be easily arranged in the conductive resin layer.

[0020] The external electrode may further include a second covering layer disposed on the first covering layer. When the external electrode includes the second covering layer, reliability during mounting on a substrate is further improved.

[0021] The green body may have a bottom surface and end surfaces adjacent to and opposite to the bottom surface, and the external electrodes may be arranged at least on the bottom surface and the end surfaces. By arranging the external electrodes over at least two surfaces of the green body, the bonding strength to the substrate during mounting is further improved.

[0022] The terminal end of the lead-out portion can be exposed at the end surface of the blank, thereby making it easy to form the lead-out portion.

[0023] The type of the first resin may be different from the type of the second resin. In addition, the first resin may include a thermosetting resin, and the second resin may include a thermoplastic resin. Thus, the conductive metal portion can be formed more easily on the conductive resin layer.

[0024] The first covering layer may contain nickel, and the second covering layer may contain tin. In addition, the thickness of the first covering layer may be 100 μm or less. Thus, the lead portion of the coil and the external electrode can be easily connected by the first covering layer.

[0025] In this specification, the term "process" is not only an independent process, but also includes this term as long as the desired purpose of the process can be achieved even if it cannot be clearly distinguished from other processes. Below, the embodiment of the present invention is described based on the drawings. However, the embodiment shown below is an embodiment of an example inductor for concretizing the technical idea of ​​the present invention, and the present invention is not limited to the inductor shown below. In addition, the components shown in the claims are not limited to the components of the embodiment. In particular, the size, material, shape, and relative configuration of the constituent components described in the embodiment are not limited to this, as long as there is no particularly specific description, but are only illustrative examples. In addition, in each figure, the same figure mark is attached to the same position. Although the embodiment is divided for convenience in consideration of the ease of explanation or understanding of the key points, it is possible to perform partial substitution or combination of the structures shown in different embodiments. In Example 2 and thereafter, the description of the same matters as in Example 1 is omitted, and only the differences are described. In particular, the same effects brought about by the same structure are not mentioned in sequence in each embodiment.

[0026] [Example]

[0027] Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples.

[0028] (Example 1)

[0029] Reference Figure 1 to Figure 3 The inductor of Example 1 is described. Figure 1 This is a partially transparent schematic perspective view of the inductor 100 as viewed from the upper surface side. Figure 2 is through the inductor 100 Figure 1 A schematic cross-sectional view taken along line a-a in FIG. 1 and on a plane perpendicular to the bottom surface and the top surface. Figure 3 yes Figure 2 A partially enlarged schematic cross-sectional view of part A.

[0030] like Figure 1 As shown in FIG. 1 , the inductor 100 includes: a base body 10 having a magnetic portion including magnetic powder and a first resin; a coil 30 enclosed in the base body 10; and an external electrode 40 disposed on the surface of the base body 10 and electrically connected to the coil 30. The base body 10 includes a bottom surface 12 on the mounting surface side, an upper surface 14 facing the bottom surface 12 in the height direction (T direction), two end surfaces 16 adjacent to and substantially orthogonal to the bottom surface 12 and facing each other in the length direction (L direction), and two side surfaces 18 adjacent to and substantially orthogonal to the bottom surface 12 and the end surfaces 16 and facing each other in the width direction (W direction). The coil 30 includes a winding portion 32 formed by winding a conductor around a winding axis N and a pair of lead portions 34 led out from the winding portion 32, with the ends of the lead portions 34 exposed at the end surfaces 16 of the base body 10, respectively, and the coil 30 is enclosed in the base body 10. The pair of external electrodes 40 are arranged on the bottom surface 12, the end surface 16, the upper surface 14 and the side surface 18 of the body 10, and are connected to the terminal end of the lead portion 34 of the coil 30 exposed from the end surface 16. Figure 1 In some cases, dotted lines are used as auxiliary lines for representing curved surfaces.

[0031] like Figure 2 As shown, the conductive resin layer 42, the first covering layer 44 and the second covering layer 46 are stacked in sequence to form the external electrode 40. The conductive resin layer 42 is formed by applying a conductive resin composition containing conductive powder and a second resin to the surface of the blank 10, and is electrically connected to the terminal portion of the lead-out portion 34 of the coil exposed at the end face 16. The conductive powder may contain silver (Ag) particles, for example. The volume average particle size of the Ag particles may be, for example, greater than 10 nm and less than 100 μm. The conductive powder may contain nano-sized Ag particles, may contain micron-sized Ag particles, or may contain both. In addition, the second resin may contain, for example, a thermoplastic resin such as an acrylic resin. The first covering layer 44 may contain, for example, nickel, and is formed on the conductive resin layer 42 by electroplating. The second covering layer 46 may contain, for example, tin, and is formed on the first covering layer by electroplating.

[0032] exist Figure 3 FIG. 3 schematically shows the connection state between the terminal end of the lead-out portion 34 and the external electrode 40. Figure 2As shown in FIG. 3 , the covering layer 24 is removed from the terminal portion of the lead portion 34 exposed at the end face 16, and the conductor 22 is exposed at the end face 16. A conductive resin layer 42 is arranged on the surface of the exposed conductor 22. The conductive resin layer 42 is formed of a conductive powder 62 and a second resin 64, and further includes a conductive metal portion 66. A plurality of conductive metal portions 66 are formed in the conductive resin layer 42 in a branched shape, for example. In the conductive resin layer 42, in addition to electrically connecting the conductor 22 and the first covering layer 44 by the proximity and contact of the conductive powder 62, the conductive metal portion 66 directly connects the conductor 22 and the first covering layer 44. For example, the branch-shaped conductive metal portion 66 is formed as follows. When the conductive resin layer 42 is formed, voids are formed due to the curing shrinkage, thermal shrinkage, etc. of the second resin. Here, the voids in the conductive resin layer 42 can also be formed by irradiating the conductive resin layer 42 with a laser to remove a part of the second resin. Thereafter, when the first covering layer 44 is formed by electroplating, the metal constituting the first covering layer 44 is electroplated and grown in the gaps of the conductive resin layer 42 to form a branch-like conductive metal portion 66. That is, the conductive metal portion 66 can be formed integrally with the first covering layer 44. The conductive metal portion 66 can also be arranged in a mesh shape in the conductive resin layer 42. The conductive metal portion 66 arranged in a mesh shape can be arranged along the interface between the particles of the conductive powder 62. In one embodiment, the conductive resin layer 42 can be configured to include a conductive powder and a second resin to form a porous structure, and the conductive metal portion 66 that directly connects the conductor constituting the coil to the first covering layer is arranged in the gaps of the porous structure. In addition, by forming the conductive resin layer 42 into a porous structure, the contact between the conductive powders 62 can be increased, thereby reducing the connection resistance. At least a portion of the conductive metal portion 66 can directly connect the terminal portion of the lead-out portion 34 to the first covering layer 44, or it can not be directly connected. It is preferable that the conductive metal portions 66 are dispersedly formed in the conductive resin layer 42 , and it is preferable that the conductive metal portions 66 are formed to have many branches.

[0033] The thickness of the conductive resin layer 42 may be, for example, 50 nm to 100 μm, or 1 μm to 20 μm. The thickness of the first cover layer may be, for example, 30 μm to 30 μm, or 0.5 μm to 15 μm. The thickness of the second cover layer may be, for example, 50 μm to 30 μm, or 1 μm to 30 μm.

[0034] like Figure 2As shown, the conductor 22 forming the coil 30 has a covering layer 24 on the surface, and the shape of the cross section orthogonal to the extension direction (length direction) of the conductor can be a roughly rectangular shape defined by thickness and width. The thickness of the conductor can be, for example, greater than 0.01 mm and less than 1 mm. The width of the conductor can be, for example, greater than 0.1 mm and less than 2 mm. The aspect ratio (width / thickness) of the conductor cross section can be, for example, greater than 1 / 1, or greater than 1 / 1 and less than 30 / 1. In addition, the covering layer 24 covering the conductor 22 is formed of an insulating resin such as polyimide, polyamide-imide, etc., having a thickness of, for example, greater than 2 μm and less than 20 μm. In order to prevent the unwinding of the winding portion, a welding layer containing a self-welding component such as a thermoplastic resin or a thermosetting resin can also be further provided on the surface of the covering layer 24, and its thickness can also be formed to be greater than 1 μm and less than 8 μm.

[0035] The winding portion 32 of the coil 30 is spirally wound so that both ends of the conductor are located at the outermost circumference, one surface defined by the width of the conductor becomes the outer circumference side, and the other surface becomes the inner circumference side, and is wound into two upper and lower sections connected at the innermost circumference and with the surfaces defined by the thickness of the conductor facing each other (so-called α winding). The coil 30 is enclosed in the blank 10 in such a manner that the winding axis N of the winding portion 32 is substantially orthogonal to the bottom surface 12 and the upper surface 14 of the blank 10.

[0036] like Figure 1 as well as Figure 2 As shown, the lead portion 34 has its front end portion led out from the outermost peripheral portion of the upper section on the upper surface 14 side of the winding portion 32 toward one side surface 18 of the blank, so that the surface defined by the width of the conductor 22 is exposed at the end surface 16 of the blank 10. The lead portion 34 has its front end portion led out from the outermost peripheral portion of the lower section on the bottom surface 12 side of the winding portion 32 toward one side surface 18 of the blank, so that the surface defined by the width of the conductor 22 is exposed at the end surface 16 of the blank 10. The cover layer 24 is removed from the surface of the conductor 22 exposed from the end surface 16.

[0037] The blank 10 may have a substantially rectangular parallelepiped shape. As for the size of the blank 10, the length L is, for example, greater than 1 mm and less than 3.4 mm, preferably greater than 1 mm and less than 3 mm, the width W is, for example, greater than 0.5 mm and less than 2.7 mm, preferably greater than 0.5 mm and less than 2.5 mm, and the height T is, for example, greater than 0.5 mm and less than 2 mm, preferably greater than 0.5 mm and less than 1.5 mm. As for the size of the blank, specifically, L×W×T may be, for example, 1 mm×0.5 mm×0.5 mm, 1.6 mm×0.8 mm×0.8 mm, 2 mm×1.2 mm×1 mm, 2.5 mm×2 mm×1.2 mm.

[0038] The magnetic part constituting the blank 10 is formed of a composite material containing magnetic powder and a first resin. As the magnetic powder, it is possible to use iron-based metal magnetic powders such as Fe, Fe-Si, Fe-Ni, Fe-Si-Cr, Fe-Si-Al, Fe-Ni-Al, Fe-Ni-Mo, Fe-Cr-Al, etc., metal magnetic powders of other composition systems, metal magnetic powders such as amorphous, metal magnetic powders whose surfaces are covered with insulating layers such as glass, metal magnetic powders whose surfaces are modified, and nano-level tiny metal magnetic powders. In addition, as the first resin, it is possible to use thermosetting resins such as epoxy resins, polyimide resins, and phenolic resins, and thermoplastic resins such as polyethylene resins, polyamide resins, and liquid crystal polymers. The filling rate of the magnetic powder in the composite material is, for example, 50% by mass or more and 85% by mass or less, preferably 60% by mass or more and 85% by mass or less, or 70% by mass or more and 85% by mass or less.

[0039] A protective layer may be arranged on the surface of the blank 10. The protective layer may be arranged on the surface of the blank outside the area where the external electrodes are arranged, or on the surface of the blank outside the area where the terminal portion of the lead portion is exposed. The protective layer may be composed of, for example, a resin. As the resin constituting the protective layer, thermosetting resins such as epoxy resins, polyimide resins, and phenolic resins, and thermoplastic resins such as acrylic resins, polyethylene resins, and polyamide resins may be used. The protective layer may also contain a filler. As the filler, non-conductive fillers such as silicon oxide and titanium oxide may be used. For example, a resin composition containing a resin and a filler is applied to the surface of the blank by coating, impregnation, or the like, and the applied resin is cured as needed to form a protective layer. The protective layer may also be formed of an inorganic material. In addition, the protective layer may also be formed in an area other than the area where the magnetic powder is exposed as described later.

[0040] The blank 10 may be marked (not shown). The marking may be given, for example, to the side of the upper surface 14 of the blank where the lead portion 34 is led out from the lower stage of the winding portion 32 to indicate the polarity of the inductor. The marking may be given, for example, by printing, laser marking, or the like.

[0041] For example, the inductor 100 can be manufactured by a manufacturing method including the following steps: a coil forming step of forming a conductor into a desired shape to form a coil; a green body forming step of embedding the formed coil in a composite material including magnetic powder and resin so that the terminal portion of the lead portion is exposed and pressing the green body by using a metal mold or the like; and an external electrode forming step including forming a conductive resin layer on the terminal portion of the lead portion exposed on the surface of the green body and forming a first covering layer on the conductive resin layer. In order to form the branch-like conductive metal portion, the following method can be used: a conductive resin paste is applied, and when the conductive resin paste is cured, the second resin is contracted to form a void, and then, when the first covering layer is formed by electroplating, the void plated in the conductive resin layer 42 is also grown.

[0042] (Example 2)

[0043] Reference Figure 4 as well as Figure 5 The inductor according to the second embodiment will be described. Figure 4 is a schematic cross-sectional view of the inductor 110 . Figure 5 yes Figure 4 The inductor 110 of the second embodiment is similar in structure to the inductor 100 of the first embodiment except that a magnetic powder exposed region is provided on a part of the surface of the green body and an external electrode is also formed in the magnetic powder exposed region.

[0044] like Figure 4 As shown in FIG. 1 , in the inductor 110, a magnetic powder exposed region 52 is formed over a portion of the bottom surface 12, a portion of the upper surface 14, a portion of the side surface 18, and the end surface 16 of the green body, and the external electrode 40 is disposed on the magnetic powder exposed region 52. In addition to the magnetic powder exposed region 52, a magnetic powder non-exposed region 54 is formed on the surface of the green body. A protective layer may be disposed on the magnetic powder non-exposed region 54.

[0045] For example, the magnetic powder exposed area 52 is formed by subjecting a desired area of ​​the green body to laser irradiation or the like. Alternatively, the magnetic powder exposed area 52 may be formed by subjecting a desired area of ​​the green body to sandblasting or the like. In the magnetic powder exposed area 52, at least a portion of the insulating layer covering the magnetic powder may be removed to expose the surface of the metal particles constituting the magnetic powder. Alternatively, in the magnetic powder exposed area 52, a portion of the first resin constituting the green body may be removed to expose the magnetic powder on the green body surface.

[0046] exist Figure 5 FIG. 5 schematically shows the connection state between the magnetic powder exposed area 52 and the external electrode 40. Figure 5As shown, a conductive resin layer 42 is arranged on the magnetic powder exposed area 52. The conductive resin layer 42 includes a conductive powder 62, a second resin 64, and a conductive metal part 66. The conductive metal part 66 connects the magnetic powder in the magnetic powder exposed area 52 to the first covering layer 44. In one embodiment, the conductive resin layer 42 can be configured as follows: it includes a conductive powder and a second resin to form a porous structure, and a conductive metal part 66 that connects the magnetic powder constituting the blank to the first covering layer is arranged in the gap of the porous structure. In the magnetic powder exposed area 52, the anchoring effect is improved because the surface roughness becomes larger. In addition, the magnetic powder is directly connected to the first covering layer. As a result, the bonding strength of the external electrode 40 relative to the blank is improved. In addition, in the magnetic powder exposed area, the conductive metal part does not necessarily connect the magnetic powder to the first covering layer, and in this case, the DC resistance can also be reduced.

[0047] (Example 3)

[0048] Reference Figure 6 The inductor according to the third embodiment will be described. Figure 6 1 is a schematic cross-sectional view of the inductor 120. The inductor 120 of the third embodiment has the same structure as the inductor 100 of the first embodiment except that the external electrodes are arranged on a part of the bottom surface 12 and a part of the end surface 16 instead of the upper surface 14 and the side surface 18.

[0049] In the inductor 120, the external electrode 40 is arranged over a portion of the bottom surface 12 and a portion of the end surface 16. This can reduce the fillet formed when mounting on a substrate, and enables higher-density mounting.

[0050] In the above-mentioned inductor, the case where the external electrodes are arranged at least over the bottom surface and end surface of the blank is described, but it can also be arranged only on the bottom surface of the blank. The end surface of the conductor in the extension direction can also be exposed on the side of the blank. The terminal end of the lead portion can also be exposed on the bottom surface of the blank instead of the end surface of the blank. Although the cross-section of the conductor perpendicular to the extension direction is rectangular, it is not limited to a rectangular shape, and the corners can also be chamfered, and each side can also be composed of curves such as semicircles and semi-ovals. The shape of the winding portion of the coil observed from the winding axis direction can also be a shape other than an oblong, for example, it can be a circle, an ellipse, a chamfered polygon, etc. A recess (foot) can be formed in the area of ​​the bottom surface of the blank where the external electrode is not arranged. The recess provided on the bottom surface of the blank can also be semicircular in shape in the height T direction when observed from the width W direction.

Claims

1. An inductor comprising: A green body having a magnetic portion including magnetic powder and a first resin; a coil having a winding portion formed by winding a conductor and a pair of lead portions led out from the winding portion, wherein the coil is enclosed in the blank; and A pair of external electrodes are connected to at least the terminal end of the lead portion on the surface of the body. The external electrode includes a conductive resin layer and a first covering layer disposed on the conductive resin layer. The conductive resin layer comprises conductive powder and a second resin. The conductive resin layer includes a plurality of conductive metal parts made of the same material as the first covering layer. The conductive powder electrically connects the terminal of the lead portion to the first covering layer, and the conductive metal portion directly electrically connects the terminal of the lead portion to the first covering layer. The surface of the green body on which the external electrode is arranged has a magnetic powder exposed portion where the magnetic powder is exposed. At least a portion of the exposed magnetic powder is connected to the first covering layer via the conductive metal portion.

2. The inductor according to claim 1, wherein The conductive metal portion is arranged in a branch shape.

3. The inductor according to claim 1, wherein: The external electrode further includes a second covering layer disposed on the first covering layer.

4. The inductor according to any one of claims 1 to 3, wherein: The blank has a bottom surface and an end surface, the end surface is adjacent to the bottom surface and the end surfaces are opposite to each other, The external electrode is disposed at least on the bottom surface and the end surface.

5. The inductor according to claim 4, wherein: A terminal end portion of the lead portion is exposed at the end surface.

6. The inductor according to any one of claims 1 to 3, wherein: The first resin is of a different type from the second resin.

7. The inductor according to any one of claims 1 to 3, wherein: The first resin includes a thermosetting resin, and the second resin includes a thermoplastic resin.

8. The inductor according to claim 3, wherein: The first covering layer includes nickel, and the second covering layer includes tin.

9. The inductor according to any one of claims 1 to 3, wherein: The thickness of the first covering layer is less than 100 μm.

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