Inductor

Abstract

The invention provides an inductor which is not limited by the cross section size of a coil conductor and has good electrical characteristics with low DC resistance. An inductor according to the present disclosure is provided with: a coil conductor having a winding portion around which a flat-angled wire having a substantially rectangular cross-section orthogonal to the longitudinal direction of the wire is wound, and a pair of lead-out portions led out from the winding portion; a green body containing a magnetic powder and a resin and enclosing the coil conductor; and an external electrode formed on the surface of the body and connected to the lead-out portion, the body having two main surfaces that intersect the winding axis of the winding portion of the coil conductor and face each other, the lead-out portion having a lead-out region that extends from the winding portion toward one main surface of the body and an electrode connection region that is connected to the external electrode, and the electrode connection region being in contact with the lead-out portion. A side surface of one short side of a rectangle formed along a cross section orthogonal to the long side direction of the conductive wire is exposed along one main surface of the green body, and a conductor of the conductive wire is connected to an external electrode.

Description

TECHNICAL FIELD

[0001] The present application relates to an inductor. BACKGROUND

[0002] A coil component is disclosed in Patent Literature 1, which is composed of a core in which a conductor wire is wrapped, and a pair of external electrodes provided on the surface of the core. In the coil component, the terminal faces of both end portions of the conductor wire in the length direction are connected to the external electrodes.

[0003] Patent Literature 1: Japanese Patent Application Laid-Open No. 2019-4174

[0004] In the coil component having the above-described structure, since the terminal faces of the conductor wire are connected to the external electrodes, the contact area of the external electrodes with the conductor wire is limited by the cross-sectional dimension of the conductor wire, and the direct current resistance value as the coil component is limited. SUMMARY

[0005] An object of the present application is to provide an inductor having good electrical characteristics with a low direct current resistance, which is not limited by the cross-sectional dimension of a conductor wire.

[0006] One embodiment of the present application is an inductor including: a coil conductor having a winding portion in which a flat angle-shaped conductor wire having a substantially rectangular cross section orthogonal to the length direction of the conductor wire is wound, and a pair of lead-out portions led out from the winding portion; a core containing a magnetic powder and a resin, and enclosing the coil conductor; and an external electrode formed on the surface of the core and connected to the lead-out portions. The core has two main faces intersecting and opposing the winding axis of the winding portion of the coil conductor. The lead-out portions have a lead-out region extending from the winding portion toward one of the main faces of the core, and an electrode connection region connected to the external electrode. For the electrode connection region, one side surface of a rectangle formed along the cross section orthogonal to the length direction of the conductor wire is exposed along the one main face of the core, and the conductor of the conductor wire is connected to the external electrode.

[0007] Furthermore, in the present specification, the entire contents of Japanese Patent Application No. 2023-136388 filed on August 24, 2023 are incorporated by reference.

[0008] According to the present application, an inductor having good electrical characteristics with a low direct current resistance, which is not limited by the cross-sectional dimension of a coil conductor, can be provided. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 is a perspective view of an inductor of one embodiment of the present application, viewed from the upper surface side of the core.

[0010] Figure 2 is a perspective view of the inductor as viewed from the bottom surface side of the blank.

[0011] Figure 3 is a perspective view showing the internal structure of the inductor.

[0012] Figure 4 is a schematic view of the manufacturing process of the inductor.

[0013] Figure 5 is a perspective view of the inductor as viewed from the direction perpendicular to the bottom surface of the blank.

[0014] Figure 6 is a perspective view of the inductor as viewed from the direction perpendicular to the end surface of the blank.

[0015] Figure 7 is a graph showing the relationship between the lead-out angle θ of the lead-out portion drawn from the winding portion and the evaluation index Ei of the electrical characteristics.

[0016] Figure 8 is a graph showing the relationship between the ratio Ra of the length of the electrode connection region to the length of the lead-out portion and the evaluation index Ei. DETAILED DESCRIPTION

[0017] Hereinafter, the structure and the manufacturing method of the inductor 1 of the embodiment will be described.

[0018] [1. Overall structure of inductor]

[0019] Figure 1 is a perspective view of the inductor 1 of the embodiment as viewed from the upper surface 12 side, Figure 2 is a perspective view of the inductor 1 as viewed from the bottom surface 10 side. The bottom surface 10 and the upper surface 12 are two opposing main surfaces of the blank 2.

[0020] The inductor 1 of the embodiment is configured as a surface mounting type electronic component, and has a blank 2 of a generally rectangular parallelepiped shape as one mode of a generally hexahedral shape, and a pair of external electrodes 4 provided on the surface of the blank 2.

[0021] Hereinafter, in the blank 2, one main surface as a mounting surface facing a not-illustrated mounting substrate at the time of mounting is defined as a bottom surface 10, and the other main surface opposite to the bottom surface 10 is referred to as an upper surface 12. In addition, a pair of outer surfaces orthogonal to the bottom surface 10 is referred to as an end surface 14, and a pair of outer surfaces orthogonal to these bottom surface 10 and the pair of end surfaces 14 is referred to as a side surface 16. The pair of end surfaces 14 are disposed opposite to each other. In addition, the pair of side surfaces 16 are disposed opposite to each other. The bottom surface 10, the upper surface 12, the end surface 14, and the side surface 16 are each a generally rectangular shape.

[0022] As shown in Figure 1 The distance from the bottom surface 10 to the upper surface 12 is defined as the thickness T of the green sheet 2, the distance between the pair of side surfaces 16 is defined as the width W of the green sheet 2, and the distance between the pair of end surfaces 14 is defined as the length L of the green sheet 2. Further, 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. That is, the bottom surface 10 and the upper surface 12 are along the width direction DW and the length direction DL, the end surface 14 is along the width direction DW and the thickness direction DT, and the side surface 16 is along the length direction DL and the thickness direction DT. Further, the end surface 14 is contiguous to the bottom surface 10, the upper surface 12, and the pair of side surfaces 16. The side surface 16 is contiguous to the bottom surface 10, the upper surface 12, and the pair of end surfaces 14.

[0023] The nominal dimensions of the inductor 1 as a finished product are, for example, 1.4 mm in length L, 1.2 mm in width W, and 0.65 mm in thickness T.

[0024] Hereinafter, a surface along the DL direction and the DT direction is referred to as an LT surface, a surface along the DT direction and the DW direction is referred to as a TW surface, and a surface along the DL direction and the DW direction is referred to as an LW surface. Further, the cross section of the inductor 1 along the LT surface, the TW surface, and the LW surface is referred to as an LT cross section, a TW cross section, and an LW cross section, respectively.

[0025] Figure 3 is a perspective view showing the internal structure of the inductor 1.

[0026] The green sheet 2 is configured to have a coil conductor 20, and a substantially hexahedral magnetic core 30 in which the coil conductor 20 is embedded, and a molded inductor in which the coil conductor 20 is enclosed in the magnetic core 30.

[0027] The magnetic core 30 is compression-molded into a substantially hexahedral molded body by pressure and heat applied to a mixed powder in which magnetic particles (magnetic powder) and resin are mixed, in a state in which the coil conductor 20 is enclosed.

[0028] Further, the magnetic particles of the present embodiment contain both a first magnetic particle of a large particle having a soft magnetic body and a relatively large average particle diameter, and a second magnetic particle of a small particle having a relatively small average particle diameter. Thereby, at the time of compression molding, the second magnetic particle as the small particle enters between the first magnetic particle as the large particle together with the resin, so that the filling rate of the magnetic particles in the magnetic core 30 can be increased, and the permeability can be improved.

[0029] In the present embodiment, the average particle diameter of the metal particles of the first magnetic particles is 20 μm or more and 28 μm or less, and the average particle diameter of the metal particles of the second magnetic particles is 1 μm or more and 6 μm or less. Further, it is preferable that the average particle diameter of the first magnetic particles be 21.4 μm or more and 27.4 μm or less, and it is preferable that the average particle diameter of the second magnetic particles be 1.5 μm or more and 1.8 μm or less. In addition, the magnetic particles can also be composed of particles having an average particle diameter different from those of the first magnetic particles and the second magnetic particles, or particles having three or more particle diameters.

[0030] The first magnetic particles and the second magnetic particles are each a particle having a metal particle, an oxide film covering the surface of the metal particle, and an insulating film covering the surface of the oxide film. By covering the metal particle with the oxide film and the insulating film, the insulation resistance and the voltage resistance can be improved.

[0031] In the first magnetic particles of the present embodiment, the metal particle uses Fe-Si-B amorphous alloy powder. The oxide film of the first magnetic particles is composed of two layers of a SiO layer and Fe2SiO4, and the thickness of the entire oxide film is 20 nm or more and 155 nm or less. In addition, the insulating film of the first magnetic particles is formed of phosphate glass having a thickness of 10 nm or more and 50 nm or less.

[0032] In addition, in the second magnetic particles of the present embodiment, the metal particle uses carbonyl iron powder. The oxide film of the second magnetic particles is iron oxide formed by oxidizing the surface of the carbonyl iron powder as the metal particle. In addition, the insulating film of the second magnetic particles is a sol-gel reaction product having silicon dioxide as a component. Thus, the slipperiness of the surface of the second magnetic particles is improved, and the entry of the second magnetic particles between the first magnetic particles can be facilitated in the green body molding and curing process of the green body 2 described later. As a result, the density of the magnetic material in the magnetic core 30 can be further increased, and the relative permeability of the magnetic core 30 can be further increased.

[0033] Further, in the first magnetic particles, the metal particle can use Fe-Si-Cr 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.

[0034] In addition, in the first magnetic particles, the insulating film can use phosphoric acid, zinc phosphate, manganese phosphate, glass, or resin.

[0035] The material of the resin included in the mixed powder of the present embodiment includes bisphenol A type epoxy resin and rubber-modified epoxy resin. Thus, an inductor 1 having both improved strength and toughness of the green body 2 can be manufactured.

[0036] In the present embodiment, the magnetic powder included in the mixed powder has the first magnetic particles in an amount of 70% by weight or more and 85% by weight or less and the second magnetic particles in an amount of 15% by weight or more and 30% by weight or less, based on the total weight of the magnetic particles included in the mixed powder. In addition, the resin included in the mixed powder is in an amount of 2.0% by weight or more and 3.5% by weight or less, based on the total weight of the magnetic powder and the resin. Further, it is preferable that the first magnetic particles be in an amount of 70% by weight or more and 80% by weight or less and the second magnetic particles be in an amount of 20% by weight or more and 30% by weight or less. In addition, it is preferable that the resin be in an amount of 2.7% by weight or more and 30% by weight or less.

[0037] As shown in FIG. 1, the coil conductor 20 has a winding portion 22 in which a wire is wound around a bobbin Q, and a pair of lead portions 23 which are led out from the winding portion 22. The winding portion 22 spirally winds the wire in two layers of upper and lower layers along the bobbin Q, and includes two winding regions 22a, 22b which overlap along the bobbin Q. The winding regions 22a and 22b are connected by the wire at a part of their inner peripheries. The wire is led out from the outer periphery of the winding portion 22 to become the lead portions 23. The lead portions 23 each include a lead region 23a which extends from the winding portion 22 toward the bottom surface 10 of the blank 2, and an electrode connection region 23b which is a wire portion connected to the external electrode 4 described later. Figure 3

[0038] The coil conductor 20 is embedded in the blank 2 so that the bobbin Q of the winding portion 22 extends along the thickness direction DT of the blank 2. That is, the bobbin Q is orthogonal to the bottom surface 10 and the upper surface 12, and extends in a direction along the end surface 14 and the side surface 16.

[0039] The wire constituting the coil conductor 20 is composed of a conductor, and a cover layer formed on the surface of the conductor. The wire is a flat angle wire having a rectangular shape in cross section orthogonal to the longitudinal direction of the wire, and has a wide surface composed of a side surface along one long side of the rectangular shape in cross section. The wire is wound so that the wide surface is parallel to the bobbin Q. The conductor is a strip conductor having a rectangular shape in cross section, and is made of copper. The thickness of the conductor is 52 μm or more and 118 μm or less, and the width is 110 μm or more and 180 μm or less. The cover layer is composed of an insulating layer formed on the surface of the strip wire, and a fusion layer formed on the surface of the insulating layer for bonding the strip wires overlapping each other in the winding portion 22 to each other. The insulating layer is composed of, for example, a polyamide-imide resin, and has a thickness of 3 μm. In addition, the fusion layer is composed of, for example, a polyamide resin, and has a thickness of 1 μm or more and 25 μm or less.

[0040] The two lead portions 23 are each led out from the winding portion 22 to the bottom surface 10, and are electrically connected to the external electrode 4 via the electrode connection region 23b exposed on the bottom surface 10.

[0041] ​A pair of external electrodes 4 are formed on the bottom surface 10 of the green body 2, respectively. The external electrodes 4 are not limited to this, but can be so-called L-shaped electrodes composed of L-shaped members extending from the bottom surface 10 to the adjacent end surface 14. Alternatively, the external electrodes 4 can be five-surface electrodes extending from the bottom surface 10 to the upper surface 12 via the adjacent end surface 14 and side surface 16.

[0042] The external electrodes 4 are electrically connected to the wiring of the circuit substrate by a suitable mounting method such as soldering. The detailed structure of the inductor 1 will be described later, and in the present embodiment, the side surface of one short side of the oblong shape of the wire constituting the coil conductor 20 along the cross section orthogonal to the long direction is exposed from the green body 2, and the conductor of the wire is connected to the external electrode 4.

[0043] In addition, a green body protective layer (not shown) is formed on the surface of the green body 2 except for the range of the external electrodes 4. The green body protective layer is, for example, a resin in which a phenoxy resin is added to a novolak resin, and contains nanosilica as a filler. The green body protective layer is formed on the surface of the green body 2 to a thickness of 10 μm or more and 30 μm or less. Further, the thickness of the green body protective layer is preferably 10 μm or more and 20 μm or less, and more preferably 15 μm or less.

[0044] The inductor 1 of such a structure can improve the DC superposition characteristics by using a soft magnetic material as the magnetic particles, and thus can be used as an electronic component of a circuit through which a large current flows, a choke coil of a DC-DC converter circuit, a power supply circuit, and the like, and can be used as an electronic component of an electronic device such as a personal computer, a DVD player, a digital camera, a TV, a mobile phone, a smartphone, a car electronics, a medical and industrial equipment, and the like. However, the use of the inductor 1 is not limited to this, and for example, can be used for a tuning circuit, a filter circuit, a rectification smoothing circuit, and the like.

[0045] [2. Outline of manufacturing process of inductor]

[0046] Figure 4 is an outline view of the manufacturing process of the inductor 1.

[0047] As shown in the drawing, the manufacturing process of the inductor 1 includes a coil conductor forming process, a preform forming process, a green body molding and curing process, a green body polishing process, and an external electrode forming process.

[0048] The coil conductor forming process is a process in which the coil conductor 20 is formed from a wire. In this process, the coil conductor 20 is formed into a shape having the above-described winding portion 22 and lead-out portion 23 by winding the wire in a winding manner called "alpha winding". The alpha winding refers to a state in which the wire is spirally wound in two layers so that the lead-out portion 23 at which the winding of the wire as a conductor starts and ends is located at the outer periphery. The number of turns of the coil conductor 20 is not particularly limited.

[0049] The preform forming step is a step of forming a preform called a tablet.

[0050] The preform is formed into a solid shape by pressing the mixed powder described above as a material of the blank 2, and in the present embodiment, a first tablet in which the coil conductor 20 can be arranged in an appropriate shape (for example, an E shape or a T shape, etc.), and a second tablet in which the coil conductor 20 is sandwiched between the first tablet in an appropriate shape (for example, an I shape or a plate shape, etc.) are formed.

[0051] The blank forming and curing step is a step of making the first tablet, the coil conductor, and the second tablet into one by setting the first tablet, the coil conductor, and the second tablet to a forming mold, and pressing them in a direction in which the first tablet and the second tablet overlap while heat is applied, so as to cure them. Thus, the blank 2 in which the coil conductor 20 is enclosed in the magnetic core 30 is formed. In addition, the blank 2 obtained by this step can be barrel polished to remove burrs and the like generated in the blank 2, or the corners of the blank 2 can be chamfered.

[0052] The blank polishing step is a step of polishing the side surface 16 of the blank 2 to adjust the width W of the blank 2. In the blank polishing step, the blank 2 is sandwiched from above and below by upper and lower grindstones of a polisher while being held by a plate-shaped member called a holding plate. By operating the polisher in this state so as to rotate the upper and lower grindstones, the side surface of the blank 2 is polished.

[0053] The external electrode forming step is a step of forming the external electrode 4 on the blank 2, and includes a blank protective layer forming step, a surface treatment step, and a plating layer forming step.

[0054] The blank protective layer forming step is a step of coating the entire surface of the blank 2 with an insulating resin.

[0055] The surface treatment step is a step of modifying the surface of the electrode predetermined position by irradiating laser light to the surface of the magnetic core 30. Here, the electrode predetermined position refers to a range of the surface of the magnetic core 30 where the external electrode 4 should be formed, including the portion of the electrode connecting region 23b exposed. Specifically, by irradiating laser light, the green sheet protective layer of the surface of the green sheet 2 and the cover layer of the electrode connecting region 23b of the coil conductor 20 are removed in the range of the electrode predetermined position, and the resin of the surface of the magnetic core 30 is removed, and the insulating film of the surface of the magnetic particle exposed from the magnetic core 30 is removed. Thus, the exposed area of the metal of the magnetic particle per unit area of the surface of the magnetic core 30 increases in the portion of the electrode predetermined position of the surface of the magnetic core 30 compared to the other surface portions of the magnetic core 30. Further, cleaning processing (for example, etching processing) for cleaning the surface of the electrode predetermined position can be performed after the irradiation of the laser light.

[0056] In the plating layer forming step, a copper plating layer is formed in the electrode predetermined position where the laser light is irradiated by roll plating copper on the surface of the magnetic core 30. In addition to this, a Ni plating layer and a Sn plating layer can be further provided on the copper plating layer to form a plating layer.

[0057] [3. Detailed structure of inductor]

[0058] Hereinafter, the inductor 1 in the present embodiment will be further described in detail.

[0059] As described above, in the coil member of the related art exemplified in Patent Document 1, the terminal surface of the leading end of the wire constituting the coil conductor is connected to the external electrode. In the conventional coil member having the above-described structure, the contact area of the external electrode with the coil conductor is limited by the size of the terminal surface of the above-described coil conductor, and the direct current resistance value as the coil member is limited.

[0060] In contrast to this, in the inductor 1 of the present embodiment, the lead-out portion 23 that is drawn from the winding portion 22 toward the bottom surface 10 of the green sheet 2 has an electrode connecting region 23b in which the side surface of the wire is exposed from the bottom surface 10. Further, the above-described exposed side surface of the wire of the electrode connecting region 23b is connected to the external electrode 4. Thus, in the inductor 1, the contact area of the external electrode 4 with the electrode connecting region 23b can be enlarged without being limited by the size of the terminal surface of the leading end of the wire, and thus the direct current resistance value of the inductor 1 can be reduced to achieve good characteristics compared to the related art.

[0061] Figure 5 is a plan view of the inductor 1 as viewed from the bottom surface 10 side. Figure 3 is a plan view of the inductor 1 as viewed from the bottom surface 10 side. Figure 6 is a plan view of the inductor 1 as viewed from the bottom surface 10 side. Figure 5The side view of the inductor 1 shows one example of the structure of the lead-out portion 23 drawn from the winding region 22a on the upper surface 12 side. Further, in order to simplify the drawing and make understanding easy, the illustration of the external electrode 4 is omitted in Figure 5

[0062] As shown in Figure 3 , Figure 5 , and Figure 6 , the electrode connection region 23b of each of the pair of lead-out portions 23 is exposed from the bottom surface 10 and connected to the corresponding external electrode 4.

[0063] As shown in Figure 6 , the lead-out portion 23 connected from the winding region 22a has a lead-out region 23a drawn from the winding portion 22 by bending the outermost peripheral wire of the winding region 22a in the direction of the bottom surface 10. Further, for a portion of the lead-out portion 23 led out to the bottom surface 10, the side surface of the flat angle-shaped wire constituting the lead-out portion 23 is exposed from the bottom surface 10 and extends along the bottom surface 10, constituting one electrode connection region 23b.

[0064] Further, on the other end surface 14 side opposite to the end surface 14 shown in Figure 6 , the same as described above, the other lead-out portion 23 connected from the winding region 22b has a lead-out region 23a drawn from the winding portion 22 by bending the outermost peripheral wire of the winding region 22b in the direction of the bottom surface 10. Further, for a portion of the lead-out portion 23 led out to the bottom surface 10, the side surface of the flat angle-shaped wire constituting the lead-out portion 23 is exposed from the bottom surface 10 and extends along the bottom surface 10, constituting the other electrode connection region 23b.

[0065] In the present embodiment, as shown in Figure 3 , the side surface of the electrode connection region 23b exposed from the bottom surface 10 and connected to the external electrode 4 is the side surface of one short side of a rectangle formed along the cross section of the flat angle-shaped wire constituting the lead-out portion 23 orthogonal to the long side direction.

[0066] Figure 3 The structure shown has the advantage that the manufacturing process is not complicated because the wire does not need to be twisted when making the coil constituted by the flat wire like the winding portion 22. In addition, Figure 3 The structure of the present embodiment can reduce the degree of shielding of the magnetic flux generated along the bobbin Q in the winding portion 22 by the wire of the lead-out portion 23 compared to the structure in which the side surface of one long side of a rectangle formed along the cross section of the wire orthogonal to the long side direction is connected to the external electrode 4. As a result, in the inductor 1, good inductance characteristics can be achieved.

[0067] [4. Evaluation of the electrical characteristics of the inductor] ​

[0068] In the inductor 1 configured as described above, the longer the length of the electrode connection region 23b that is exposed from the surface of the bottom surface 10 and extends, the smaller the direct current resistance of the connecting portion of the electrode connection region 23b and the external electrode 4. However, in the case where the length of the electrode connection region 23b is lengthened, there is a possibility that other electrical characteristics of the inductor 1, such as inductance, direct current superimposed current, and the like, are affected due to, for example, a decrease in the volume of the magnetic core 30 including a magnetic body that configures the core 2.

[0069] Therefore, the inventors of the present application conducted a simulation-based study on the relationship between the structure of the lead-out portion 23 including the electrode connection region 23b and the electrical characteristics of the inductor 1. Referring to Figure 6 , as parameters that give an influence on the electrical characteristics of the inductor 1, the inventors paid particular attention to the angle, that is, the lead-out angle θ, formed by the extension direction of the wire of the outermost periphery of the winding portion 22 that extends toward the lead-out portion 23 and the extension direction of the lead-out region 23a of the lead-out portion 23 that is led out from the winding portion 22 toward the bottom surface 10, and the ratio Ra (= Lc / Lp) of the length Lc of the electrode connection region 23b with respect to the length Lp of the lead-out portion 23.

[0070] The lead-out angle θ is defined, for example, as the bending angle formed by a first extension direction Va of the wire of the outermost periphery of the winding portion 22 that extends toward the lead-out portion 23 and a second extension direction Vb of the lead-out region 23a of the lead-out portion 23 that is led out from the first extension direction Va and extends toward the bottom surface 10. The lead-out angle θ can be measured, for example, as the angle (θa shown in FIG. 6) formed by a surface Sa formed by the contour of the winding portion 22 and the side surface of the core 2 on the upper surface 12 side that configures the lead-out region 23a of the lead-out portion 23. Figure 6

[0071] In addition, the length Lp of the lead-out portion 23 is defined, for example, as the length from a point A that is the intersection point of a line segment along the extension direction of the side surface of the bottom surface 10 side of the lead-out region 23a and the surface Sa of the winding portion 22, to a point C that is the terminal point on the bottom surface 10 of the lead-out portion 23, via a point B that is the position of the bottom surface 10 side at which the lead-out region 23a and the electrode connection region 23b are connected. In addition, the length Lc of the electrode connection region 23b can be defined, for example, as the length of the lead-out portion 23 measured along the side surface of the bottom surface 10 side, and the length of the portion exposed from the surface of the bottom surface 10 (i.e., the length from the point B to the point C).

[0072] An evaluation criterion that indicates the merit or demerit of the electrical characteristics uses an index Ei calculated by the following equation (1).

[0073] Ei = Li x Isat ÷ Rdc (1) ​

[0074] In the above-described formula (1), Li, Isat, and Rdc are the inductance, the DC superimposed current, and the DC resistance of the inductor 1, respectively.

[0075] The better the electrical characteristics, that is, the larger the inductance Li, the larger the DC superimposed current Isat, or the smaller the DC resistance Rdc, the larger the index Ei becomes.

[0076] [4.1 Production of a sample]

[0077] In order to evaluate the electrical characteristics of the inductor 1, the inventors produced a core 2, and based on the produced core 2, varied the lead-out angle θ and the ratio Ra in simulation to calculate the index Ei.

[0078] The core 2 for simulation was produced as follows.

[0079] The mixed powder of which the material of the magnetic core 30 is composed used a metal magnetic powder in which a Fe-Si-Cr alloy powder as first magnetic particles and a carbonyl iron powder as second magnetic particles were mixed. According to the measurement results based on a particle size distribution meter, the average particle diameter of the first magnetic particles of the metal magnetic powder of the example was 25.3 μm, and the average particle diameter of the second magnetic particles was 1.7 μm. In addition, the resin of the example contained a bisphenol A type epoxy resin and a rubber-modified epoxy resin, which accounted for 2.7 wt% in the mixed powder. According to the measurement by the inventors, the relative magnetic permeability of the mixed powder was 34, and the saturation magnetic flux density was 1.36 T. Furthermore, the relative magnetic permeability was measured using a high-frequency signal of a frequency of 1 MHz using a BH analyzer and an impedance material analyzer. In addition, the saturation magnetic flux density was measured using an LCR tester and a DC power source to measure the inductance change at the time of superimposition, to inversely calculate the BH data, and to take the value of the magnetic flux saturation as the saturation magnetic flux density of the mixed powder.

[0080] The wire used for the coil conductor 20 was a flat angle-shaped wire of which the cross section orthogonal to the long side direction of the wire was substantially rectangular, and the dimensions of the rectangle of the cross section were 0.128 mm and 0.083 mm in length and width, respectively. The coil conductor 20 was formed in a shape having a winding portion 22 formed as an alpha winding of two layers, and a lead-out portion 23. The winding portion 22 was formed to include two winding regions 22a, 22b superimposed along the winding shaft Q by spirally winding the wire as an alpha winding of two layers up and down along the winding shaft Q. The lead-out angle θ of the lead-out portion 23 led out from the outer periphery of the winding portion 22 was 90 degrees.

[0081] The core 2 was produced using the above-described magnetic core 30 and coil conductor 20. The winding shaft Q of the winding portion 22 of the coil conductor 20 was in a posture substantially perpendicular to the mounting surface, that is, the bottom surface 10 of the core 2.

[0082] The distance L1 from the end position (point C) of the electrode connection area 23b of the lead-out section 23 to the nearest side 16 of the blank 2 (refer to) Figure 6 The thickness is 100 μm. The terminal position of the electrode connection region 23b is set at this position because if the terminal position is closer to the side 16 than this position, the wall thickness of the side 16 in this part will become thinner, and the billet will be prone to cracks or defects, and the mechanical strength of the billet 2 cannot be maintained at a practical level.

[0083] The distance L2 between the starting point A of the lead-out section 23 and the side 16 opposite to the side 16 of the end position closest to the electrode connection region 23b (refer to) Figure 6 ) is W / 3.

[0084] [4.2 Evaluation Results]

[0085] First, the relationship between the angle θ and the index Ei is evaluated.

[0086] Figure 7 This is the simulation result of the index Ei relative to the extraction angle θ. Figure 7 In the diagram, the horizontal axis represents the angle θ, and the vertical axis represents the index Ei. During the calculation, the distances L1 and L2 are the same as those used for the aforementioned sample, being 100 μm and W / 3, respectively.

[0087] like Figure 7 As shown, in the range where the take-up angle θ is below 90 degrees, the value of index Ei increases with the increase of the take-up angle θ. Moreover, index Ei reaches its peak at a take-up angle θ of 90 degrees and decreases as the take-up angle θ exceeds 90 degrees. Here, the increase of index Ei in the range where the take-up angle θ is below 90 degrees is due to the increase in the length of the electrode connection region 23b with the increase of the take-up angle θ, while the DC resistance Rdc decreases.

[0088] Furthermore, the index Ei decreases in the region where the lead-out angle θ exceeds 90 degrees because if the lead-out angle θ exceeds 90 degrees, the position of the lead-out portion becomes a shape that wraps back from the winding direction of the winding portion. Therefore, the direction of the current flowing through the lead-out portion 23 is opposite to the direction of the current in the wire of the winding portion 22 to which the lead-out portion is connected. Also, the volume of the magnetic core 30 of the magnetic body in the blank body 2 decreases accordingly as the length of the electrode connection region 23b increases. Therefore, the inductance Li and the DC overlap current Isat decrease.

[0089] Therefore, according to Figure 7 The results shown indicate that the preferred extraction angle θ is below 90 degrees.

[0090] In addition, in the case where, for example, a power inductor for a DC-DC converter circuit that requires a particularly small DC resistance and a large DC superimposed current is assumed as the use of the inductor 1, from the viewpoint of maintaining the power efficiency of the DC-DC converter circuit at a level that is not a problem in practice, it is preferable that the index Ei be 0.0662 (in Figure 7 the figure shown by the dotted line) or more.

[0091] Therefore, the lead-out angle θ is according to Figure 7 more preferably 30 degrees or more and 90 degrees or less.

[0092] Next, the relationship between the ratio Ra of the length Lc of the electrode connection region 23b to the length Lp of the lead-out portion 23 and the index Ei is evaluated.

[0093] Table 1 is a simulation result of the index Ei in the case where the ratio Ra is changed while the lead-out angle θ is fixed. In the simulation of Table 2, in a state where the lead-out angle θ and the distance Ll are respectively fixed at 90 degrees and 100 μm, which are the same as those of the above-described sample, the distance L2 is increased from W / 3 (i.e., the start point A is moved to the left in the figure), the length Lc of the electrode connection region 23b is changed, and thus the ratio Ra is changed. Figure 6

[0094] In addition, Table 2 is a simulation result of the index Ei in the case where the lead-out angle θ is changed while the distances Ll and L2 are fixed. In the simulation of Table 1, the distances Ll and L2 are the same as those of the above-described sample, and are respectively 100 μm and W / 3.

[0095] [Table 1]

[0096]

[0097] [Table 2]

[0098]

[0099] Figure 8 A graph of the relationship between the ratio Ra and the index Ei is drawn in accordance with the results shown in Table 1 and Table 2. In Figure 8 , the horizontal axis is the ratio Ra, and the vertical axis is the index Ei. In Figure 8 , the graphs G1 and G2 are graphs in which Table 1 and Table 2 are respectively drawn.

[0100] In Figure 8 , the state where the ratio Ra shown by the horizontal axis is 0.58 corresponds to a state where the lead-out angle θ, the distance Ll, and the distance L2 are respectively 90 degrees, 100 μm, and W / 3, which are the same as those of the above-described sample.

[0101] In addition, in​Figure 8 The same as the use of the inductor 1 assumes the lower limit value 0.0662 of the index Ei in the case of the power inductor of the DC-DC converter circuit. Figure 7

[0102] In either case of the graph G1 and the graph G2, the length of the electrode connection region 23b increases as the ratio Ra increases, so as shown in Figure 8 the index Ei increases as the ratio Ra increases. According to the results shown in Figure 8 it is clear that as a range capable of corresponding to the use as the power inductor of the DC-DC converter circuit and capable of securing the mechanical strength of the green compact 2 to a practical level, the ratio Ra is preferably 0.25 or more and 0.58 or less.

[0103] Furthermore, all of the above-described embodiments and modified examples exemplify one mode of the present application, and can be arbitrarily modified and applied within the scope of the gist of the present application. In addition, any elements of the above-described embodiments can be combined, as a new embodiment.

[0104] In addition, unless otherwise specified, the directions, various values, shapes, materials, and the like in the above-described embodiments include a range that functions identically to these directions, values, shapes, and materials (so-called equivalent range).

[0105] [Structure supported by the above-described embodiments]

[0106] The above-described embodiments support the following structure.

[0107] (Structure 1) An inductor comprising: a coil conductor having a winding portion in which a flat angle-shaped wire having a substantially rectangular cross section orthogonal to a long side direction of the wire is wound, and a pair of lead-out portions led out from the winding portion; a green compact containing a magnetic powder and a resin, and enclosing the coil conductor; and an external electrode formed on a surface of the green compact and connected to the lead-out portions, the green compact having two main surfaces intersecting and opposing a winding axis of the winding portion of the coil conductor, the lead-out portions having a lead-out region extending from the winding portion toward one of the main surfaces of the green compact, and an electrode connection region connected to the external electrode, for the electrode connection region, a side surface along one short side of a rectangle formed along the cross section orthogonal to the long side direction of the wire is exposed along the one main surface of the green compact, and a conductor of the wire is connected to the external electrode.

[0108] According to the inductor of Structure 1, it is possible to achieve good electrical characteristics with a low direct current resistance without being limited by the cross-sectional size of the wire constituting the coil conductor.

[0109] ​According to the inductor described in Structure 2, the angle formed by the face formed by the profile of the winding portion and the other main face side face of the lead-out region is 90 degrees or less.

[0110] According to the inductor of Structure 2, good electrical characteristics in which inductance, direct current superimposed current, and direct current resistance are balanced are achieved.

[0111] According to the inductor described in Structure 2, the angle formed by the face formed by the profile of the winding portion and the other main face side face of the lead-out region is 90 degrees or less.

[0112] According to the inductor of Structure 3, electrical characteristics suitable for use as a power inductor for a DC-DC converter circuit are achieved.

[0113] According to the inductor described in Structure 4, the ratio of the length of the electrode connection region to the length of the lead-out portion is 0.25 or more and 0.58 or less.

[0114] According to the inductor of Structure 4, the wall thickness of the core between the end of the electrode connection region and the outside of the core is ensured, the mechanical strength of the core is maintained at a practical level, and electrical characteristics suitable for use as a power inductor for a DC-DC converter circuit are achieved.

[0115] According to the inductor described in Structure 5, the winding portion is formed by winding the wire in two layers along the winding shaft.

[0116] According to the inductor of Structure 5, the lead-out portion is led out from the outermost periphery of the winding portion, and good electrical characteristics in which the direct current resistance is lower are achieved.

[0117] Explanation of Reference Numerals

[0118] 1... inductor, 2... core, 4... external electrode, 10... bottom surface (one main face), 12... upper surface (other main face), 14... end surface, 16... side surface, 20... coil conductor, 22... winding portion, 22a, 22b... winding region, 23... lead-out portion, 23a... lead-out region, 23b... electrode connection region, 30... magnetic core, Q... winding shaft.

Claims

1. An inductor, wherein, have: A coil conductor having a wound portion and a pair of leads extending from the wound portion, wherein the wound portion is wound with a wire having a cross-section that is approximately rectangular with flat angles and orthogonal to the long side direction of the wire. A blank containing magnetic powder and resin, and internally encapsulating the aforementioned coil conductor; and An external electrode is formed on the surface of the blank and connected to the lead-out portion. The aforementioned blank has two main surfaces that intersect and are opposite to the spool of the winding portion of the aforementioned coil conductor. The aforementioned lead-out portion has a lead-out area extending from the aforementioned winding portion toward one of the aforementioned main surfaces of the blank, and an electrode connection area connected to the aforementioned external electrode. For the aforementioned electrode connection area, the side of one short side of a rectangle formed by a cross-section orthogonal to the long side of the aforementioned wire is exposed along one of the aforementioned main surfaces of the aforementioned blank, and the conductor of the aforementioned wire is connected to the aforementioned external electrode.

2. The inductor according to claim 1, wherein, The angle formed by the outline of the winding portion and the other main surface side opposite to the main surface of the blank, and the other main surface side side of the conductor constituting the lead-out area, i.e., the lead-out angle, is less than 90 degrees.

3. The inductor according to claim 2, wherein, The aforementioned lead-out angle is above 30 degrees and below 90 degrees.

4. The inductor according to any one of claims 1 to 3, wherein, The ratio of the length of the electrode connection area to the length of the lead-out portion is 0.25 or more and 0.58 or less.

5. The inductor according to any one of claims 1 to 4, wherein, The winding section is constructed by winding the conductor in two layers along the aforementioned spool, with the wide surface of the conductor parallel to the aforementioned spool.

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