JP6610818B2 - Inductor element and manufacturing method thereof - Google Patents

Description

  The present invention relates to an inductor element in which a winding portion wound in a coil shape is integrated inside a core portion made of a magnetic material, and a method for manufacturing the same.

  As the inductor element, a surface mount type inductance element used as a circuit element such as a DC / DC converter mounted on a personal computer or a portable electronic device is known.

  As an example of this inductor element, an inductor in which a coil is embedded in a dust core (a core obtained by insulating the surface of a metal magnetic powder and press-molding) obtained by press-molding a metal magnetic powder with a binder. Devices are known. Since this inductor element has a structure in which the terminal electrode is in direct contact with the dust core, the metal magnetic powder is required to have insulation. For this reason, the surface of the metal magnetic powder particles is subjected to insulation treatment, and further coated with a binder, and then the metal magnetic powder is pressure-molded.

  In Patent Document 1 below, in order to achieve both high insulation and high magnetic permeability, the air core part of the coil (the inner peripheral part of the winding part) is more permeable than the first magnetic body constituting the outer side of the core part. A structure in which a second magnetic body having a high magnetic permeability is arranged has been proposed.

  However, in this conventional structure, after forming the second magnetic body, the first magnetic body is disposed in the air core portion of the coil, and then the first magnetic body and the winding portion are surrounded. The body is molded. For this reason, in the conventional structure, in order to shape | mold a 2nd magnetic body separately from a 1st magnetic body, there exists a problem that a process cost and member cost rise.

Further, in this conventional example, there is a problem that peeling occurs from a boundary surface between the second magnetic body and the first magnetic body or cracks are generated. The following points can be considered as the cause of the problem.
1) Since the second magnetic body is obtained by pressure-molding metal magnetic powder, the surface becomes relatively smooth and the adhesiveness with the first magnetic body is poor.
2) Since the second magnetic body is made of different materials having different magnetic permeability, the second magnetic body has a different expansion coefficient from that of the first magnetic body.
Moreover, in patent document 2 shown below, in the pressure molding process, the molding process has two stages using different molds, and in the same manner as in the above example, the first molding process and the second molding process. Insufficient adhesion of the magnetic material occurs at the boundary between the obtained surfaces, and there is a risk of peeling or cracking at the boundary surface.

  In addition, since at least selective pressure is not applied to the inside of the coil, the inside of the coil is not sufficiently pressurized. For this reason, cracks are likely to occur inside the coil. Further, in the second molding step, a pressure force is directly applied to the coil existing inside the core, and the coil is crushed, thereby causing a failure of the coil insulation coating and possibly causing a short circuit failure.

Japanese Patent Laid-Open No. 2003-168610 JP 2010-10425 A

  The present invention has been made in view of such a situation, and an object of the present invention is to provide an inductor element that is less likely to cause cracks, has a high initial permeability, and is less likely to cause a short circuit, and the inductor element can be easily manufactured at low cost. It is to provide a method for manufacturing an inductor element that can be manufactured.

In order to achieve the above object, a method for manufacturing an inductor element according to the present invention includes:
A step of preparing an insert member having a winding portion in which a conductor is wound in a coil shape and at least a pair of lead portions protruding outward from the winding portion;
Preparing granules containing magnetic powder and binder;
Placing the insert member such that the winding portion is located inside the mold cavity and the lead portion is located outside the cavity; and
Filling the interior of the cavity in which the insert member is disposed with the granules;
Compression molding is performed by applying pressure to the inside of the cavity so that the density of the magnetic powder existing in the inner peripheral part of the winding part is higher than the density of the magnetic powder located in the outer peripheral part of the winding part. And a step of performing.

  In the inductor element manufacturing method according to the present invention, the granules located at the inner peripheral portion and the outer peripheral portion of the winding portion are compression-molded in the cavity so that the granules can freely move relative to each other. There is no clear interface between the peripheral portion and the outer peripheral portion, and cracks are unlikely to occur. Further, in the method of the present invention, after forming the compression molded body once, there is no step of changing the shape of the compression molded body again.

  Further, in the method of the present invention, excessive pressure is not applied to the coiled conductor existing inside the core, and the coiled conductor is less likely to be crushed. Short circuit failure is unlikely to occur. Furthermore, in the inductor element obtained by the method of the present invention, the density of the magnetic powder present in the inner peripheral part of the winding part is higher than the density of the magnetic powder located in the outer peripheral part of the winding part, As a result, the inventors have found that the initial permeability is improved.

  Preferably, after the cavity is filled with a part of the whole amount of the granules to be filled in the cavity, the insert member is disposed in the cavity, and then the cavity is filled with the granules. Fulfill. By filling the granules into the cavity in this order, the insert member having the winding portion can be easily placed in the cavity without using a spacer or the like, which contributes to a reduction in manufacturing cost.

  The type of granules to be filled before the insert member is arranged inside the cavity and the type of granules to be filled inside the cavity after the insert member is arranged inside the cavity may be the same type, but characteristics etc. May be different. For example, the particle size of the magnetic powder in the granules to be filled first may be smaller than the particle size of the magnetic powder in the granules to be filled later. Or you may make the elasticity of the granule filled initially higher than the elasticity of the granule filled later. Alternatively, the amount of binder in the granules to be filled first may be smaller than the amount of binder in the granules to be filled later. Or you may make the hardness of the binder in the granule filled initially larger than the hardness of the binder in the granule filled later. By configuring as described above, the density of the magnetic powder in the inner peripheral portion of the winding portion can be increased as compared with the outer peripheral portion.

  Preferably, the granules located on the inner periphery of the winding part are selectively compressed inside the cavity filled with the granules. Before, after, or simultaneously, pressure is applied to the granules located entirely inside the cavity. By selectively compressing the granules located at the inner peripheral part of the winding part, the density of the magnetic powder at the inner peripheral part of the winding part can be increased compared to the outer peripheral part. Further, since selective compression and overall compression are performed simultaneously or continuously, it is difficult to cause cracks or the like in the molded body.

Preferably, the mold is
A main punch that compresses the granules located inside the cavity from both sides in the winding axis direction of the winding portion and a sub-portion that is smaller than the inner diameter of the winding portion and is relatively movable with respect to the main punch. A punch, and
By moving the sub punch in the direction toward the inside of the cavity with respect to the main punch, the granules located on the inner peripheral portion of the winding portion are selectively compressed.

  By performing selective compression in this way, the density of the magnetic powder at the inner peripheral portion of the winding portion can be easily increased as compared with the outer peripheral portion.

  A part of the total amount of the granules to be filled in the cavity and the granules filled in the cavity thereafter may have the same characteristics or different characteristics.

Inductor element according to the present invention,
It is manufactured by the manufacturing method according to any of the above,
The density of the magnetic powder existing in the inner peripheral part of the winding part is higher than the density of the magnetic powder located in the outer peripheral part of the winding part.

The inductor element according to the present invention is
A winding portion in which a conductor is wound in a coil shape;
A core portion formed by compression-molding granules containing magnetic powder and a binder, integrally covering and covering the inner and outer peripheral portions of the winding portion and both ends of the winding shaft;
An inductor element having a lead portion drawn out of the core portion from the winding portion and connected to the conductor,
The density of the magnetic powder is different between the inner peripheral portion and the outer peripheral portion of the winding portion in the core portion,
The density of the magnetic powder in the core portion located in the inner peripheral portion of the winding portion is higher than the density of the magnetic powder in the core portion located in the outer peripheral portion of the winding portion. To do.

Preferably, the density of the magnetic powder in the core portion located in the inner peripheral portion of the winding portion is 0 than the density of the magnetic powder in the core portion located in the outer peripheral portion of the winding portion. .1 g / cm ³ or higher. In such a relationship, the initial permeability of the inductor element is improved.

  The average particle diameter of the magnetic powder in the core part located in the inner peripheral part of the winding part is made smaller than the magnetic powder in the core part located in the outer peripheral part of the winding part. Also good. Alternatively, the elasticity of the magnetic powder in the core portion located in the inner peripheral portion of the winding portion is increased compared to the magnetic powder in the core portion located in the outer peripheral portion of the winding portion. Also good.

  The magnetic powder in the core portion located at either one of both end surfaces along the winding axis of the winding portion is characterized in that the characteristic of the magnetic powder in the core portion located in the inner peripheral portion of the winding portion is The same characteristics may be used.

FIG. 1 is an overall perspective view of an inductor element according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view taken along the line II-II shown in FIG. FIG. 3 is a flowchart showing a manufacturing process of the inductor element according to the embodiment of the present invention. 4A is a schematic cross-sectional view of a mold before filling in the manufacturing process shown in FIG. FIG. 4B is a schematic cross-sectional view of the mold showing a step continued from FIG. 4A. FIG. 4C is a schematic cross-sectional view of the mold showing a step continued from FIG. 4B. FIG. 4D is a schematic sectional view of a mold showing a step subsequent to FIG. 4C. FIG. 5 is a schematic cross-sectional view of the insert molded body taken out from the mold. FIG. 6A is a schematic cross-sectional view of a mold showing a manufacturing process of an inductor element according to another embodiment of the present invention. FIG. 6B is a schematic cross-sectional view of the mold showing a step continued from FIG. 6A. FIG. 6C is a schematic cross-sectional view of the mold showing a step continued from FIG. 6B. FIG. 6D is a schematic sectional view of a mold showing a step subsequent to FIG. 6C. FIG. 6E is a schematic cross-sectional view of a mold showing a step subsequent to FIG. 6D. FIG. 7A is a schematic cross-sectional view of a mold showing a manufacturing process of an inductor element according to a comparative example of the present invention. FIG. 7B is a schematic cross-sectional view of the mold showing a step continued from FIG. 7A. FIG. 7C is a schematic cross-sectional view of the mold showing a step continued from FIG. 7B. FIG. 7D is a schematic sectional view of a mold showing a step subsequent to FIG. 7C. FIG. 8 is a graph showing the relationship between the inner / outer density difference of the inductor element and the DC superposition characteristics according to the embodiment of the present invention.

Hereinafter, the present invention will be described based on embodiments shown in the drawings.
First embodiment
As shown in FIGS. 1 and 2, an inductor element 2 according to an embodiment of the present invention includes a core portion 4 as a compression molded body, and a winding in which a conductor 6 a is wound in a coil shape inside the core portion 4. Part 6. The conductor 6a is composed of, for example, a conductive wire and an insulating coating layer that covers the outer periphery of the conductive wire as necessary.

  The conducting wire is made of, for example, Cu, Al, Fe, Ag, Au, phosphor bronze, or the like. The insulating coating layer is made of, for example, polyurethane, polyamideimide, polyimide, polyester, polyester-imide, polyester-nylon, or the like. The cross-sectional shape of the conductor 6a is not particularly limited, and examples thereof include a circular shape and a rectangular shape.

  The core part 4 is formed by compression-molding granules containing magnetic powder and a binder. Although it does not specifically limit as magnetic powder, Ferrite, such as Mn-Zn and Ni-Cu-Zn, Sendust (Fe-Si-Al; Iron-silicon-aluminum), Fe-Si-Cr (Iron-silicon-chromium) ), Permalloy (Fe-Ni) and the like. The binder is not particularly limited, and examples thereof include epoxy resins, phenol resins, polyimides, polyamide imides, silicon resins, and combinations thereof.

  As shown in FIG. 2, the winding portion 6 is a portion in which one or more conductors 6a are wound in a coil shape. From the winding portion 6, at least a pair of lead portions 6b that are both ends of the conductor 6a are provided. , Pulled out of the core 4. In the illustrated embodiment, a pair of lead portions 6 b are drawn from the winding portion 6 along the X-axis direction, and the tips of the lead portions 6 b located outside the core portion 4 are along the outer surface of the core portion 4. It is bent and connected to the pair of terminal electrodes 8 by means of welding or conductive adhesive. In the present embodiment, each terminal electrode 8 is made of a conductive plate having an L-shaped cross section, and is in close contact with and joined to the side surface and the lower surface of the core portion 4.

  In the present embodiment, the lower surface of the core portion 4 is formed substantially parallel to a plane passing through the mutually perpendicular X axis and Y axis, and the winding axis of the winding portion 6 is a plane passing through the X axis and the Y axis. Are substantially parallel to the Z axis perpendicular to the axis. In the present embodiment, the upper surface of the core portion 4 is substantially parallel to the lower surface, and the four side surfaces are substantially perpendicular to the upper and lower surfaces. However, in the present invention, the shape of the core portion 4 is not particularly limited, and is not limited to a hexahedron, and may be a cylindrical shape, an elliptical column, a polygonal column, or the like.

  As shown in FIG. 2, in this embodiment, the core part 4 is configured to integrally cover the inner and outer peripheral parts of the winding part 6 and both ends of the winding shaft. In addition, the density of the magnetic powder is different between the inner peripheral part 4a and the outer peripheral part 4b of the winding part 6, and the density of the magnetic powder in the core part 4 located in the inner peripheral part 4a of the winding part is It is higher than the density of the magnetic powder in the core part 4 located in the outer peripheral part 4b of the part 6.

Preferably, the density Din of the magnetic powder in the core part 4 located in the inner peripheral part 4a of the winding part 6 is higher than the density Dout of the magnetic powder in the core part 4 located in the outer peripheral part 4b of the winding part 6. 0.1 g / cm ³ or more, more preferably 0.2 g / cm ³ or more. That is, the internal / external density difference Dd (= Din−Dout) defined by the formula Dd = Din−Dout is 0.1 g / cm ³ or more, more preferably 0.2 g / cm ³ or more. In such a relationship, the initial permeability of the inductor element is improved. Further, from the viewpoint of improving the direct current superposition characteristics of the inductor element, the inner / outer density difference Dd is preferably 0.25 g / cm ³ or more. The direct current superimposition characteristic is an index indicating the difficulty of decreasing the inductance when a direct current is passed through the inductor element. Generally, the direct current is applied to the element from 0, and the current 0 It can be evaluated by the value (Idc1 / ampere) of the current that flows when the inductance falls to 80% with respect to the inductance (μH). The larger this value, the better the DC superposition characteristics.

  The size of the inductor element 2 of the present embodiment is not particularly limited. For example, the X-axis direction width is 1.0 to 20 mm, the Y-axis direction width is 1.0 to 20 mm, and the height is 1.0 to 10 mm.

  The inductor element 2 can be used as a circuit element such as a DC / DC converter mounted on a personal computer or a portable electronic device, for example.

Next, a method for manufacturing the inductor element 2 shown in FIGS. 1 and 2 will be described with reference to FIGS. 3, 4A to 4D, and FIG.
4A is a schematic cross-sectional view of the mold 10 in the state of step S1 in the flowchart shown in FIG. As shown in FIG. 4A, the mold 10 of this embodiment includes a lower main punch 12 and an upper lower punch 14. The main punches 12 and 14 are arranged so as to be movable relative to the lower outer frame 15 and the upper outer frame 16 in the vertical direction in the Z-axis direction. Moreover, as shown in FIG. 4A, the lower outer frame 15 is combined with the upper outer periphery of the lower main punch 12, and the upper outer frame 16 is disposed on the lower outer frame 15. A cavity 20 is formed inside the outer frames 15 and 16.

  A lower secondary punch 18 is disposed at the center of the X-axis and Y-axis planes of the lower main punch 12 so as to be relatively movable up and down in the Z-axis direction. In FIG. 4A, the upper end surface in the Z-axis direction of the lower sub punch 18 is arranged so as to be drawn with a step of depth dx with respect to the upper end surface in the Z-axis direction of the lower main punch 12. The depth dx is determined according to the size of the inductor element 2 shown in FIGS. 1 and 2, particularly the height thickness t0 in the Z-axis direction, and is determined so as to satisfy dx / t0 = 0.05 to 0.6. It is preferred that

  Next, in this embodiment, as shown in step S2 shown in FIG. 3, the first filling of granules is performed. In the first filling of the granules, as shown in FIG. 4B, a part 4A of the whole amount of the granules to be filled in the cavity 20 is filled in the cavity 20. Thereafter, the winding portion 6 as an insert member is placed inside the cavity 20 and a part of the total amount of the granule so that the winding axis of the winding portion 6 substantially coincides with the moving axis of the lower auxiliary punch 18. Place on 4A. The lead portion 6b from the winding portion 6 may be configured to be sandwiched between the split surfaces of the outer frames 15 and 16, and after molding, the lead portion 6b is taken out together with the molded body.

  The outer diameter d1 of the lower auxiliary punch 18 is preferably in a predetermined relationship with respect to the inner diameter d0 of the winding portion 6. For example, d0 / d1 is preferably 1 or more, more preferably from 1. It is 5 or less, particularly preferably 1.1 to 5. If d0 / d1 is smaller than 1, the internal crack occurrence rate tends to be high and the short-circuit occurrence rate tends to be high, and if d0 / d1 is too large, the effect of the present invention tends to be small.

  Next, in this embodiment, as shown in step S3 shown in FIG. 3, the second filling of the granules is performed. In the second filling of the granules, as shown in FIG. 4C, the remaining 4B of the total amount of the granules to be filled in the cavity 20 is filled. As a result, the inside of the cavity 20 is filled with the granules 4A and 4B.

  In the present embodiment, the granules 4A and 4B are composed of the same magnetic powder and binder, the magnetic powder has the same type, particle size, structure and content, and the binder type and content is also the same. The same. In the present embodiment, the magnetic powder is a metal magnetic particle, and the outer periphery of the particle is preferably coated with an insulating film. Examples of the insulating film include a metal oxide film and a resin film. The particle size of the magnetic powder is preferably 0.5 to 50 μm.

  The binder content in the magnetic powder is preferably about 2.0 to 5.0 parts by weight of the binder with respect to 100 parts by weight of the magnetic powder. The granules filled in the cavity 20 may contain a solvent, a plasticizer, a lubricant, an antioxidant, a flame retardant, a heat stabilizer and the like in addition to the magnetic powder and the binder.

Next, in this embodiment, as shown in step S4 shown in FIG. The applied pressure between the upper main punch 14 and the lower main punch 12 is preferably 0.1 to 1 ton / cm ² (1 to 10 MPa). Thereafter or simultaneously, the lower secondary punch is raised in step S5 shown in FIG. This state is shown in FIG. 4D.

  As shown in FIG. 4D, in the present embodiment, the lower secondary punch 18 is moved upward in the Z-axis direction with respect to the lower main punch 12 until the upper surface of the lower secondary punch 18 coincides with the upper surface of the lower main punch 12 ( In the direction of entering the cavity 20). In the case of this embodiment, the relative movement amount of the lower sub punch 18 with respect to the lower main punch 12 in the Z-axis direction matches the depth dx of the step shown in FIG. 4A.

  Further, in accordance with the amount of movement, the granules located on the inner peripheral part 4 a of the winding part 6 are compressed more greatly than the granules located on the outer peripheral part 4 b of the winding part 6. As a result, the density of the magnetic powder in the core portion 4 located in the inner peripheral portion 4a of the winding portion is higher than the density of the magnetic powder in the core portion 4 located in the outer peripheral portion 4b of the winding portion 6. .

  In the embodiment described above, as shown in FIG. 4D, the lower secondary punch 18 is moved so that the upper surface thereof coincides with the upper surface of the lower main punch 12, and the lower surface of the molded body is wound so that it is flush with the flat surface. Although the granule located in the inner peripheral part of the line part 6 was compressed, it is not necessary to make it correspond. In the above-described embodiment, the lower auxiliary punch is provided only for the lower main punch 12, but the upper main punch 14 may be provided with the same upper auxiliary punch. In any case, with respect to the granules located in the inner peripheral part of the winding part 6 arranged inside the cavity 20 in a state in which the free fluidity of the granules is secured inside the cavity 20, the outer circumference What is necessary is just to pressurize the inside of the cavity 20 so that a pressure may become higher than the granule located in a part.

After that, as shown in step S6 shown in FIG. 3, the granules existing inside the cavity 20 are pressurized under high pressure in a direction in which the upper and lower main punches 12 and 14 are close to each other. At the time of the high pressure pressing, as shown in FIG. 4D, the lower sub punch 18 is pressed toward the upper main punch in conjunction with the lower main punch 12. The applied pressure during high-pressure pressing is preferably ^{2 to 10} ton / cm ²
(20 to 100 MPa).

  Thereafter, in step S7 shown in FIG. 3, the lower outer frame shown in FIG. 4D is lowered in the Z-axis direction together with the lower main punch 12 and the lower auxiliary punch 18, and the core portion 4 is compressed as shown in FIG. The molded insert molded body is taken out. Thereafter, the insert molded body is heat-treated to cure the binder resin made of a thermosetting resin. Thereafter, the lead portion 6 shown in FIG. 5 is cut to a predetermined length as necessary, connected to the terminal electrode 8 shown in FIG. 2, the terminal electrode 8 is bent, and is brought into close contact with the outer surface of the core portion 4. Terminal electrodes that can be surface-mounted. In this way, the inductor element 2 shown in FIGS. 1 and 2 can be manufactured.

  In the method for manufacturing the inductor element 2 according to the present embodiment, the granules positioned on the inner peripheral portion and the outer peripheral portion of the winding portion 6 are compression-molded in the cavity 20 so that the granules can freely move relative to each other. Therefore, there is no clear interface between the inner peripheral portion and the outer peripheral portion, and cracks are unlikely to occur. Moreover, in the method of this embodiment, after forming a compression molding body once, it does not have the process of changing the shape of the compression molding body again, Therefore In this respect, it is hard to generate | occur | produce a crack.

  In the method of the present embodiment, excessive pressure is not applied to the coiled conductor existing inside the core, and the coiled conductor is less likely to be crushed. There is little possibility of occurrence, and short circuit failure is unlikely to occur. Furthermore, in the inductor element obtained by the method of the present embodiment, the density of the magnetic powder existing in the inner peripheral part 4a of the winding part 6 is the density of the magnetic powder located in the outer peripheral part 4b of the winding part 6. It has been found by the present inventors that the initial permeability is improved as a result.

  Furthermore, in this embodiment, after a part of the whole amount of granules to be filled in the cavity is filled in the cavity 20, the winding part 6 as an insert member is arranged inside the mold, and then the cavity 20 is filled with the granule. By filling the granules into the cavity in this order, the insert member having the winding portion 6 can be easily placed in the cavity without using a spacer or the like, which contributes to a reduction in manufacturing cost.

  Moreover, in this embodiment, the granule located in the inner peripheral part of a coil | winding part is selectively compressed inside the cavity filled with the granule, and a pressure is applied to the granule located in the whole inside a cavity after that. By selectively compressing the granules located at the inner peripheral part of the winding part, the density of the magnetic powder at the inner peripheral part of the winding part can be increased compared to the outer peripheral part. Moreover, since selective compression and overall compression are performed continuously, it is difficult to cause cracks in the molded body.

  In the present embodiment, the mold 10 includes main punches 12 and 14 that compress the granules located inside the cavity 20 from both sides in the winding axis direction of the winding portion 6 and the inner diameter of the winding portion 6. The sub punch 18 having a small diameter and movable relative to the main punch 12. The sub punch 18 is moved in the direction toward the inside of the cavity 20 with respect to the main punch 12. The granules located on the inner periphery of the part 6 are selectively compressed. By performing the selective compression in this way, the density of the magnetic powder at the inner peripheral portion of the winding portion 6 can be easily increased as compared with the outer peripheral portion.

Second Embodiment In the embodiment described above, the granules in the first filling performed in step S2 shown in FIG. 3 and the granules in the second filling performed in step S3 are the same, but in this embodiment, different granules are used. Is used. Other than that, this embodiment is the same as the first embodiment described above, and has the same effects. Hereinafter, different parts will be described in detail, and a part of the description of common parts will be omitted.

  In this embodiment, as shown in FIG. 6A, after the first granule 4 </ b> Aa that is filled before the winding portion 6 as an insert member is placed inside the cavity 20, and after the winding portion 6 is placed inside the cavity 20, The second granule filled in the cavity 20 is different.

  Thereafter, as shown in FIG. 6B, low-pressure pressurization by the upper main punch 14 is performed. The applied pressure between the upper main punch 14 and the lower main punch 12 is the same as that in the first embodiment. The lower auxiliary punch 18 is raised before, after, or simultaneously with that. This state is shown in FIG. 6C.

  As shown in FIG. 6C, in the present embodiment, the lower secondary punch 18 is moved upward in the Z-axis direction with respect to the lower main punch 12 until the upper surface of the lower secondary punch 18 coincides with the upper surface of the lower main punch 12 ( In the direction of entering the cavity 20). By this movement, the first granules 4Aa enter the inner peripheral part of the winding part 6 and the granules located in the inner peripheral part are compressed more greatly than the granules located in the outer peripheral part of the winding part 6. The

  Thereafter, as shown in FIG. 6D, the granules existing inside the cavity 20 are pressurized at a high pressure in a direction in which the upper and lower main punches 12 and 14 are close to each other. Thereafter, as shown in FIG. 6E, the insert molded body in which the core portion 4 'is compression-molded is taken out. The subsequent steps are the same as those in the first embodiment.

  Pressure transmission and flow behavior during molding of a metal powder (granule) containing a binder depend on the physical properties of the granule. When the elasticity of the granule is high, the pressure punch surface has the maximum pressure (maximum density) and the pressure transmission to the inside of the molded body is gradually reduced as compared with the case where the granule elasticity is low. Therefore, in order to increase the density of the inner peripheral portion of the winding part 6, the granule 4Aa used in the first filling is preferably a highly elastic material compared to the granule 4Bb used in the second filling. As measures for making the granules 4Aa highly elastic, there are means such as 1) reducing the amount of binder to the metal powder, or 2) reducing the lubricant (such as zinc stearate).

  Alternatively, the particle size (average particle size) of the magnetic powder in the granules 4Aa to be filled first may be smaller than the particle size (average particle size) of the magnetic powder in the granules 4Bb to be filled later. Or you may select the kind of magnetic body so that the hardness of the magnetic powder in granule 4Aa filled initially may become higher than the hardness of the magnetic powder in granule 4Bb filled later. Or you may make the hardness of the binder in granule 4Aa filled initially larger than the hardness of the binder in granule 4Bb filled later.

  By comprising as mentioned above, the density of the magnetic powder in the inner peripheral part of the coil | winding part 6 can be raised further compared with an outer peripheral part. Further, the initial permeability in the inductor element is increased, and short-circuit defects are less likely to occur.

  As shown in FIG. 6E, in the inductor element according to the present embodiment, the characteristics of the magnetic powder in the core portion 4 ′ located on the inner peripheral portion of the winding portion 6 are along the winding axis of the winding portion 6. This is the same as the characteristics of the magnetic powder in the core portion 4 ′ located on either one of the both end faces (the bottom face in FIG. 6E). This is because the first granules 4Aa exist over the inner peripheral portion of the winding portion 6 and the bottom surface of the core portion 4 ′.

The present invention is not limited to the above-described embodiment, and can be variously modified within the scope of the present invention.
For example, in the above-described embodiment, the main punches 12 and 14 of the mold are arranged above and below in the vertical direction along the Z-axis direction, but the horizontal direction along the Z-axis direction or the angle between the vertical and the horizontal You may arrange in the direction.

  Hereinafter, although this invention is demonstrated based on a more detailed Example, this invention is not limited to these Examples.

Example 1
First, granules to be filled in the cavity 20 of the mold 10 shown in FIG. 4A were prepared. A silane coupling agent dissolved in water was added to 100 g of an Fe—Si—Cr alloy (average particle size 0.5 to 10 μm) as magnetic powder, and heated at 110 ° C. for 30 minutes to form an insulating film on the surface of the magnetic powder. . An epoxy resin diluted with acetone was added to the magnetic powder in an amount of 3% by weight based on the weight of the magnetic powder, and the mixture was stirred, passed through a mesh with 250 micron openings, and dried at room temperature for 24 hours to obtain magnetic powder granules.

  As shown in FIG. 4B, magnetic powder containing a binder in the mold 10 was put up to 1/3 of the mold depth (the total depth of the cavity up to the upper surface of the lower main punch 12). . At this time, the lower secondary punch 18 at the center of the lower part of the mold was lowered by about 3 mm with respect to the lower main punch 12 so that the magnetic powder increased in the vicinity of the central portion of the inner periphery of the winding portion 6. Next, the winding part 6 was set in the cavity 20 of the mold.

  Specifically, the outer diameter of the lower auxiliary punch 18 is 3.5 mm, and a winding part 6 having an inner diameter of 4 mm and a height of 3 mm is attached to a box-shaped mold of 10 mm × 10 mm × 9 mm (mold depth). Then, the magnetic powder granules were filled up to a height of 3 mm from the upper surface of the lower main punch 12 (the bottom surface of the mold of the cavity 20). After placing the winding part 6 thereon, as shown in FIG. 4C, the magnetic powder granules were filled up to a height of 9 mm from the bottom of the mold until the winding part 6 was completely filled with the granules.

Next, as shown in FIG. 4D, the upper main punch 14 was lowered and the lower auxiliary punch 18 was raised at the same time to perform pressure molding. The molding pressure was 4 ton / cm ² (about 40 MPa). Thereafter, as shown in FIG. 5, the molded body was taken out from the mold and subjected to heat treatment at 180 ° C. for 1 hour to cure the thermosetting resin (epoxy binder). The dimensions of the core part 4 were 10 mm long × 10 mm wide × 5.4 mm high.

  Thereafter, the nickel terminal electrode 8 shown in FIG. 2 is joined by welding to the lead part 6b drawn from the winding part 6 to the outside of the core part 4, the terminal part is bent, and the surface-mountable terminal electrode 8 is provided. A sample of the SMD type inductor element 2 was obtained.

  The sample of the inductor element 2 thus obtained was measured for the initial permeability, the number of cracks, the number of short-circuit defects, the density of the inner periphery of the winding part, and the density of the outer periphery of the winding part. It was. The results are shown in Table 1.

  The initial permeability was measured using a LCR meter (manufactured by Hewlett-Packard Co.) at a measurement frequency of 100 KHz and a measurement current of 0.5 mA. The average of 20 samples was calculated.

  The number of cracks was measured by observing the internal state of 20 samples by X-ray analysis (CT scan) and examining the number of cracks.

  The number of short-circuit defects is measured by measuring the inductance of 20 samples with an LCR meter from 100 kHz to 10 MHz, and the inductance when the frequency is 10 MHz is reduced by 10% or more compared to the inductance when the frequency is 100 kHz. Was judged as short.

  The density of the inner peripheral part of the winding part and the density of the outer peripheral part of the winding part were measured as follows. The prepared sample was destroyed, and the inner and outer peripheral portions of the winding portion were cut out and sampled, and then the weight and volume were measured, and the density was measured. The volume was obtained by obtaining the buoyancy from the mass difference when the mass of the object was submerged in water.

Example 2
In Example 1, the same particles were used as the granules to be filled in the cavity before placing the winding part in the cavity of the mold and the granules to be filled thereafter, but different ones were used in Example 2. A sample was prepared in the same manner as in Example 1 except for the following, and the same measurement was performed. The results are shown in Table 1.

  The granules to be filled first were produced as follows. That is, as a magnetic powder, a silane coupling agent dissolved in water is added to 100 g of an Fe—Si—Cr alloy (average particle size 0.5 to 10 μm), heated at 110 ° C. for 30 minutes, and an insulating coating is formed on the surface of the magnetic powder. Formed. An epoxy resin diluted with acetone was added to the magnetic powder in an amount of 2% by weight with respect to the weight of the magnetic powder, and the mixture was stirred, passed through a mesh with 250 micron openings, and dried at room temperature for 24 hours to obtain magnetic powder granules.

  Moreover, the granule filled up next was produced as follows. A silane coupling agent dissolved in water was added to 100 g of an Fe—Si—Cr alloy (average particle size 0.5 to 10 μm) as magnetic powder, and heated at 110 ° C. for 30 minutes to form an insulating film on the surface of the magnetic powder. . An epoxy resin diluted with acetone was added to the magnetic powder in an amount of 4% by weight based on the weight of the magnetic powder, and the mixture was stirred, passed through a mesh having a mesh size of 250 microns and dried at room temperature for 24 hours to obtain magnetic powder granules.

Further, in the second embodiment, unlike the first embodiment, as shown in FIG. 6B, the lower sub punch 18 (φ3.5 mm) with respect to the lower main punch 12 with the upper main punch 14 fixed to the upper part of the mold. ) Was raised to the bottom of the cavity, and then the inside of the cavity 20 was pressurized with an upper and lower punch pressure of 4 ton / cm ² .

  Except for the above, a sample was prepared in the same manner as in Example 1, and the same measurement was performed. The results are shown in Table 1.

Comparative Example 1
In Comparative Example 1, a sample was prepared in the same manner as in Example 1 except that the lower main punch 12 having no lower sub-punch 18, that is, the lower main punch similar to the upper main punch 14 was used. Measurements were made. The results are shown in Table 1.

Comparative Example 2
In Comparative Example 2, a sample was prepared and subjected to the same measurement as in Example 1 except that the pressure molding was performed as described below. The results are shown in Table 1. That is, in Comparative Example 2, first, as shown in FIG. 7A, the lower main punch 12a and the upper main punch 14a having the central recesses 12b and 14b on the cavity 20 side inside the outer frames 15 and 16, respectively, It was arranged to move freely.

After the granules 40 and the winding part 6 were arranged in the cavity 20 in the same manner as in Example 1, as shown in FIG. 7B, compression pressing was performed. The molding pressure was 4 ton / cm ² (about 40 MPa) as in Example 1. Thereafter, as shown in FIG. 7C, the molded body was taken out from the mold. On the compression molded body of the granules 40, convex portions 40a corresponding to the concave portions 12b and 14b of the mold are formed.

  Thereafter, as shown in FIG. 7D, using another mold apparatus having other flat main punches 12A and 14A that do not have the recesses 12b and 14b, similarly to the invention shown in Japanese Patent Application Laid-Open No. 2010-10425. Then, the compression molded body of the granules 40 was pressed again so that the convex portion 40a disappeared, and a molded body having the same dimensions as in Example 1 was obtained. Thereafter, a sample of the inductor element was obtained in the same manner as in Example 1, and the same measurement as in Example 1 was performed. The results are shown in Table 1.

As shown in Evaluation Table 1, in Examples 1 and 2, unlike Comparative Examples 1 and 2, it was confirmed that the density of the inner peripheral portion of the winding portion was improved compared to the density of the outer peripheral portion of the winding portion. did it. Furthermore, in Examples 1 and 2, it was confirmed that the occurrence of cracks and the like was less than that in Comparative Examples 1 and 2, the initial permeability was high, and short-circuit defects were less likely to occur.

Example 3
The dimensions of lowering the lower secondary punch 18 in the lower center of the mold with respect to the lower main punch 12 were adjusted, and the inner and outer density difference Dd was changed as shown in the horizontal axis of FIG. Thus, a sample of the inductor element was produced. And the result of having investigated the direct current | flow superimposition characteristic of the sample is shown in FIG. As shown in FIG. 8, from the viewpoint of improving the direct current superposition characteristics of the inductor element, it was confirmed that the internal / external density difference Dd was 0.25 g / cm ³ or more, preferably 0.26 g / cm ³ or more. .

  Note that the DC superposition characteristics are obtained by applying a direct current from 0 to each inductor element sample, and the value (ampere) of the current flowing when the current drops to 80% of the inductance (μH) at the current 0. It was set as Idc1 and evaluated by the numerical value of Idc1. Inductance was measured with an LCR meter at 100 kHz.

2 ... Inductor elements 4, 4 '... Core part 4a ... Inner peripheral part 4b ... Outer peripheral part 6 ... Winding part 6a ... Conductor 6b ... Lead part 8 ... Terminal electrode 10 ... Mold 12 ... Lower main punch 14 ... Upper main punch 15, 16 ... Outer frame 18 ... Lower secondary punch 20 ... Cavity

Claims (5)

A winding portion in which a conductor is wound in a coil shape;
A core part integrally covering the inner and outer peripheral parts of the winding part and both ends of the winding shaft;
An inductor element having a lead portion drawn out of the core portion from the winding portion and connected to the conductor,
The volume ratio occupied by the magnetic powder is different between the inner peripheral portion and the outer peripheral portion of the winding portion in the core portion,
The magnetic powder corresponding density to the volume proportion of the volume of the magnetic powder of the core portion located on the outer periphery of the winding portion is occupied by the core portion located on the inner periphery of the winding portion An inductor element characterized by being 0.26 g / cm ³ or more higher than the density corresponding to the ratio.   The elasticity of the magnetic powder in the core part located in the inner peripheral part of the winding part is higher than that of the magnetic powder in the core part located in the outer peripheral part of the winding part. The described inductor element.   The average particle size of the magnetic powder in the core portion located in the inner peripheral portion of the winding portion is smaller than that of the magnetic powder in the core portion located in the outer peripheral portion of the winding portion. 3. The inductor element according to 1 or 2.   The hardness of the magnetic powder in the core portion located in the inner peripheral portion of the winding portion is higher than that of the magnetic powder in the core portion located in the outer peripheral portion of the winding portion. 4. The inductor element according to any one of 3.   The magnetic powder in the core portion located at either one of both end surfaces along the winding axis of the winding portion is characterized in that the characteristic of the magnetic powder in the core portion located in the inner peripheral portion of the winding portion is The inductor element according to claim 1, wherein the inductor element has the same body characteristics.

Images