JP2007067214A - Power inductor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small and low-profile power inductor having a satisfactory DC superimposed performance. <P>SOLUTION: The power inductor comprises a first insulating body 41, coil conductors 31, 32 formed on the upper and the lower surface of the body 41, a second insulating body 51 formed so as to cover the coil conductors 31, 32 and the body 41, and a third insulating body 61 formed so as to cover at least the upper and the lower surface of the body 51. At least the body 61 comprises an organic resin with a flat-metal-system soft magnetic material powder included as a filler. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a high-current inductor corresponding to a current of several hundred mA to several tens of A.

Chip inductors differ in rated current, internal structure, etc. depending on their usage. For example, an inductor used in a signal line has a rated current of several mA to several tens of mA, and an inductor used in a power line or the like (referred to as a “power inductor”) has a rated current of several hundred mA to several tens of A. It has become. As a conventional chip-type power inductor, a wire-wound inductor is used (see Patent Document 1). This conventional power inductor has a structure in which a conducting wire is wound around a core made of ferrite.
JP 2003-297642 A

  By the way, with the recent miniaturization of various electronic devices, there is a strong demand for the reduction in size and height of such chip inductors. In particular, a power inductor is an essential circuit in a power supply circuit. However, as other circuit elements are rapidly becoming smaller and more highly integrated, it has not been sufficient to reduce the size and height of power inductors. This is because, when a magnetic part such as an inductor is reduced in size due to a reduction in size, the magnetic core is likely to be magnetically saturated, and the amount of current that can be handled as a power source is reduced. In addition, since the conventional wound power inductor has a basic structure in which a conducting wire is wound around the core, it is particularly difficult to reduce the height.

  Therefore, in order to reduce the size and height, it is conceivable to use a multilayer chip inductor, which has been mainly used for signal purposes, as a power source instead of the conventional wire-wound inductor. However, in conventional multilayer chip inductors, ferrite-based magnetic materials are mainly used, and this ferrite has high permeability and electrical resistance, but has a low saturation magnetic flux density. Thus, there is a characteristic that the DC superimposition characteristic is deteriorated. For this reason, the conventional multilayer chip inductor is unsuitable for use as a power source because of its structure.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a small and low-profile power inductor having good DC superposition characteristics.

  In order to achieve the above object, in the present application, in a power inductor in which a coil conductor is embedded and a terminal electrode connected to the coil conductor is formed on an outer surface of the coil body, An insulator, a coil conductor formed on the top and bottom surfaces of the first insulator, a second insulator formed so as to cover the coil conductor and the first insulator, and a second insulator A third insulator formed so as to cover at least an upper surface and a lower surface, and at least the third insulator is made of an organic resin containing a flat metal-based soft magnetic powder as a filler. We propose something that features

  The applicant measured the relationship between the material of the filler and the DC superposition characteristics in an inductor provided with an organic resin containing magnetic material powder as a filler as a magnetic material. As a result, in the case of using a metallic soft magnetic powder as a filler, the rate of change of inductance with respect to current is extremely smaller than that of ferrite, so that a high current can flow, that is, it has good DC superposition characteristics. I understood. In addition, the applicant measured the relationship between the aspect ratio of the powder and the magnetic permeability of the magnetic material in an inductor provided with an organic resin containing a metal-based soft magnetic material powder as a filler as the magnetic material. As a result, it was found that a flat powder can obtain a higher magnetic permeability than a spherical powder.

  In the present invention, the element body is formed using an organic resin containing a flat metallic soft magnetic powder as a filler as a magnetic material. As a result, the power inductor according to the present invention has an element structure suitable for miniaturization and low profile, but has good direct current superposition characteristics and is suitable for power supply applications.

  As described above, according to the present invention, since the element body is formed using an organic resin containing a flat metal soft magnetic powder as a magnetic material as a filler, it is possible to reduce the size and height. Although it has a suitable element structure, it has good direct current superposition characteristics and is suitable for use as a power source.

(First embodiment)
A first embodiment of the present invention will be described with reference to the drawings. 1 is an external perspective view of a power inductor, FIG. 2 is a cross-sectional view of the power inductor, and FIG. 3 is an exploded perspective view of a power inductor element.

  As shown in FIG. 1, the power inductor 1 includes a thin rectangular parallelepiped element body 10 in which a coil is embedded, and terminal electrodes 21 and 22 formed at both ends of the element body and connected to the coil ends, respectively. I have.

  The internal structure of the element body 10 will be described with reference to the cross-sectional view of FIG. 2 and the exploded perspective view of FIG. Note that FIG. 3 omits the layer structure of the element body 10 in order to explain the structure of the coil.

  As shown in FIG. 2 and FIG. 3, the element body 10 includes a pair of spiral coil conductors 31 and 32 disposed opposite to each other and a flat plate shape interposed between the coil conductors 31 and 32. A first insulator 41, a second insulator 51 sandwiched between the first insulator 41 and embedded in the coil conductors 31 and 32, and a second insulator 51 embedded in the second insulator 51. 3 insulators 61. In the first insulator 41 and the second insulator 51, a through hole 71 is formed in the inner peripheral portions of the coil conductors 31 and 32. This through hole is filled with a third insulator 61. The third insulator 61 filled in the through hole corresponds to the core of the coil. A third insulator 61 is also formed on the outer periphery of the first insulator layer 41 and the second insulator layer 51.

  Each insulator 41, 51, 61 has a permeability set according to the product specifications, characteristics, application, etc. of the power inductor 1. Specifically, each insulator 41, 51, 61 is made of an organic resin containing a metallic soft magnetic material as a filler, or an organic resin not containing a filler. That is, the permeability of each of the insulators 41, 51, and 61 is appropriately selected by appropriately selecting the filler content, material, and the like when the filler is contained in the organic resin. Can be set).

  In the power inductor 1 according to the present invention, since the three types of insulators 41, 51, 61 are formed in the element body 10, there are various combinations of the magnetic permeability of the insulators 41, 51, 61. As a result of the simulation, it is preferable that the relationship of the permeability of the first insulator 41 ≦ the permeability of the second insulator 51 ≦ the permeability of the third insulator 61 is satisfied. In particular, the combination of the permeability of the first insulator 41, the permeability of the second insulator 51, and the permeability of the third insulator 61 is “high / high / high”, “1 (nonmagnetic) / High and high ”,“ 1 (non-magnetic), 1 (non-magnetic) and high ”are suitable for product design.

  The organic resin used in each insulator 41, 42, 43 may be either a thermoplastic resin or a thermosetting resin. Examples of thermosetting resins include benzocyclobutene (BCB), epoxy resin, phenol resin, unsaturated polyester resin, vinyl ester resin, polyimide resin (PI), polyphenylene ether oxide resin (PPO), bismaleimide triazine cyanate ester Examples thereof include resins, fumarate resins, polybutadiene resins, and polyvinyl benzyl ether resins. Examples of thermoplastic resins include very low density polyethylene resin (VLDPE), low density polyethylene resin (LDPE), linear low density polyethylene resin (LLDPE), medium density polyethylene resin (MDPE), and high density polyethylene resin (HDPE). ), Polypropylene resin (PP), polybutene resin, polymethylpentene resin, polyvinyl alcohol resin, ethylene / vinyl alcohol copolymer, polyacrylonitrile, polyamide resin, polyacetal resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polyphenylene sulfide resin, Examples include polyetheretherketone resins, isotactic polystyrene resins, liquid crystal polymers, and the like. In particular, epoxy resin, polyimide resin (PI), and benzocyclobutene (BCB) are highly reliable because of their low dielectric constant and low dielectric loss tangent, as well as excellent chemical resistance and low water absorption. Is preferable in that it can be secured.

  Examples of the metal-based soft magnetic material contained in each of the insulators 41, 42, and 43 include pure iron (Fe), carbonyl iron (Fe—C), silicon steel (Fe—Si), permalloy (Fe—Ni), per Menjules (Fe-Co), Supermalloy (Fe-Ni-Mo), Permembers (Fe-Ni-Co), Fe-Al alloys, Fe-Al-Si (preferably Sendust (common name)), etc. . The present invention is characterized in that each particle of the metal material contained in the organic resin as a filler has a flat shape instead of a spherical shape. Here, the flat shape means that the aspect ratio is 2 or more. As a result of simulation, when such a flat metal material was used as a filler, a higher magnetic permeability was obtained compared to a spherical metal material. More specifically, the aspect ratio is desirably 2 to 60, and more desirably 10 to 30. With such insulators 41, 51, 61, the power inductor according to the present invention has excellent direct current superposition characteristics.

  As shown in FIGS. 2 and 3, lead electrodes 31 a and 32 a for connecting to the terminal electrodes 21 and 22 are formed on the outer peripheral side ends of the coil conductors 31 and 32. The lead electrodes 31 a and 32 a pass through the second insulator 51 and the third insulator 61 and are exposed on the side surfaces of the element body 10. Interlayer connection lands 31b and 32b are formed at the inner peripheral side ends of the coil conductors 31 and 32, respectively. The lands 31 b and 32 b are formed so as to surround the peripheral edge of the through hole 71. A through hole 72 is formed on the peripheral surface of the through hole 71. The coil conductor 31 and the coil conductor 32 are interlayer-connected by the through hole 72.

  As a material for each of the coil conductors 31 and 32, the through hole 72, and the terminal electrodes 21 and 22, a metal having excellent conductivity, such as Ag, Pd, Cu, Al, or an alloy thereof is used.

  Next, a method for manufacturing the power inductor 1 will be described with reference to the drawings. FIG. 4 is a diagram for explaining a manufacturing process of the power inductor 1. Here, the manufacturing method of the power inductor 1 in which the magnetic permeability of the 2nd insulator 51 and the 3rd insulator 61 differs is demonstrated.

  This manufacturing method is a method used in a conventional method for manufacturing a printed wiring board. Specifically, first, a through hole 103 corresponding to a core portion is formed in a base 101 in which an organic resin containing filler is formed in a flat plate shape, and interlayer connection of the coil conductor pattern 102 is performed on the inner peripheral surface thereof. A via 104 is formed. This base 101 corresponds to the first insulator 41. The through-hole 103 is formed by drilling, laser, sandblasting, punching, or the like. The via 104 is formed by forming a seed layer by sputtering, electroless plating or the like and further performing electrolytic plating. The seed layer may be replaced by direct plating in which electrolytic plating is performed after the palladium complex is attached.

  Next, the coil conductor pattern 102 is formed on both surfaces of the base 101 (FIG. 4A). This base 101 corresponds to the first insulator 41. As a method of forming the coil conductor pattern 102, various methods such as plating, etching, printing, and transfer used in the printed wiring board manufacturing process can be used. By the way, in the present invention, since a large current flows through the coil, the conductor wiring is desired to be as thick as possible in a limited space, and therefore the coil conductor pattern 102 is desired to be formed thick. Therefore, plating or etching is preferable as a method for forming the coil conductor pattern 102.

  Next, an organic resin layer 105 containing filler is formed on both surfaces of the base 101 by a laminating method, an isostatic pressing method, or the like (FIG. 4B). At this time, the through hole 103 is filled with an organic resin so that no void is generated. This organic resin layer 105 corresponds to the second insulator 51.

  Next, the through hole 106 corresponding to the core portion is formed on the inner peripheral side of the coil conductor pattern 102, and the through hole 107 is also formed on the outer peripheral side of the coil conductor pattern 102 (FIG. 4C). At this time, care is taken not to cut the coil conductor pattern 102.

  Next, the organic resin layer 108 containing filler is formed on both surfaces of the organic resin layer 105 by a laminating method, an isostatic pressing method, or the like (FIG. 4D). At this time, the through holes 106 and 107 are filled with an organic resin so that no voids are generated. This organic resin layer 108 corresponds to the third insulator 61.

  Next, the element body 10 is obtained by cutting the laminated body for each unit part (FIG. 4E). Finally, the power inductor 1 is obtained by forming the terminal electrodes 21 and 22 on the side surface of the element body 10 by dipping or the like.

  When a thermoplastic resin is used as the base 101 and the organic resin layers 105 and 108, the plastic temperature of the insulating resin outside the insulating resin serving as the base 101 is lower in order to prevent the inner insulating layer thickness variation due to lamination. Low is preferable.

  Next, a method for manufacturing the power inductor 1 having the same magnetic permeability of the second insulator 51 and the third insulator 61 will be described with reference to the drawings. More specifically, a case will be described in which the second insulator 51 and the third insulator 61 have exactly the same characteristics and are formed integrally. FIG. 5 is a diagram for explaining a manufacturing process of the power inductor 1.

  First, similarly to the manufacturing method, the through holes 203 corresponding to the core portions are formed on both sides of the base 201 in which the organic resin containing the filler is formed in a flat plate shape, and the outer peripheral side of the coil conductor pattern 202 is formed. A through hole 204 is also formed in the base 201. Next, the coil conductor patterns 202 are formed on both surfaces of the base 201, and the vias 205 for connecting the coil conductor patterns 102 between the inner peripheral surfaces of the through holes 203 are formed (FIG. 5A). The base 201 corresponds to the first insulator 41.

  Next, an organic resin layer 206 containing filler is formed on both surfaces of the base 201 by a laminating method, an isostatic pressing method, or the like (FIG. 5B). At this time, the through holes 203 and 204 are filled with an organic resin so that no voids are generated. The organic resin layer 206 corresponds to the second insulator 51 and the third insulator 61.

  Next, the element body 10 is obtained by cutting the laminated body for each unit part (FIG. 5C). Finally, the power inductor 1 is obtained by forming the terminal electrodes 21 and 22 on the side surface of the element body 10 by dipping or the like.

  As described above, the power inductor 1 according to the present embodiment has a structure in which a resin layer and a conductor layer are laminated in the same manner as a conventional printed wiring board, unlike a conventional winding type. Can be easily realized. In particular, the manufacturing process can be applied to the conventional manufacturing process of printed wiring boards, so that the manufacturing cost can be reduced. Specifically, since a large number of element bodies can be formed simultaneously, the manufacturing efficiency is improved as compared with a conventional wound inductor that requires a winding process one by one. In addition, since a firing step is not required, it can be manufactured with simple equipment and requires less energy for manufacturing.

  Further, in the power inductor 1 according to the present embodiment, since a flat metallic soft magnetic material is used as the filler contained in the organic resin layer, high DC superposition characteristics can be obtained even though the structure is small and low. be able to. Further, since the insulator forming the element body 10 is composed of three types of insulators, the first insulators 41, 51, and 61, various kinds of resins can be selected by appropriately selecting the resin and filler of each insulator. It becomes possible to correspond to product characteristics.

(Second Embodiment)
A power inductor according to a second embodiment of the present invention will be described with reference to the drawings. 6 is a cross-sectional view of the power inductor, and FIG. 7 is an exploded perspective view of the power inductor body.

  The power inductor 2 according to the present embodiment differs from the first embodiment in the number of coil formation layers. Specifically, in the power inductor 1 according to the first embodiment, the coil conductors 31 and 32 are embedded in the element body 10, but the power inductor 2 according to the present embodiment is shown in FIGS. As shown, coil conductors 33, 34, 35, 36 are embedded in the element body 10.

  The coil conductors 33 and 34 are formed in a state of being embedded in the third insulator 61 on the outer surface of the second insulator 51. In addition, the coil conductors 35 and 36 are formed in a state of being embedded in the second insulator 52 on the exterior surface of the first insulator 41 in the same manner as the coil conductors 31 and 32 in the first embodiment. Yes.

  Lead electrodes 33 a and 34 a for connection to the terminal electrodes 21 and 22 are formed on the outer peripheral side ends of the coil conductors 33 and 34. The extraction electrodes 34 a and 34 a penetrate the third insulator 61 and are exposed on the side surfaces of the element body 10. Lands 33b and 34b for interlayer connection with the coil conductors 35 and 36 are formed at the inner peripheral side ends of the coil conductors 33 and 34, respectively.

  Lands 35a and 36a for interlayer connection are formed on the outer peripheral side ends of the coil conductors 35 and 36, respectively. The lands 35 a and 36 a are conductively connected through vias 73 that penetrate the first insulator 41. Lands 35b and 36b for interlayer connection with the coil conductors 33 and 34 are formed at the inner peripheral side ends of the coil conductors 35 and 36, respectively. The lands 35b and 36b are electrically connected to the lands 33b and 34b of the corresponding coil conductors 33 and 34 through vias 74 and 75 that penetrate the second insulator 52, respectively. Other configurations and materials are the same as those in the first embodiment.

  Next, a method for manufacturing the power inductor 2 will be described with reference to FIG. First, by using a build-up method used in a conventional method for manufacturing a printer wiring board, a stack corresponding to the first insulator 41, the second insulator 52, the coil conductors 33 to 36, and the vias 73 to 75 is used. A body 301 is created (FIG. 8B). Next, the through holes 302 and 303 are formed on the inner and outer peripheral sides of the coil (FIG. 8C). At this time, care is taken not to cut the coil conductor pattern.

  Next, an organic resin layer 304 containing filler is formed on both surfaces of the laminate 301 by a laminating method, an isostatic pressing method, or the like (FIG. 8C). At this time, the through holes 302 and 303 are filled with an organic resin so that no voids are generated. This organic resin layer 304 corresponds to the third insulator 61.

  Next, the element body 10 is obtained by cutting the laminated body for each unit part (FIG. 8D). Finally, the power inductor 2 is obtained by forming the terminal electrodes 21 and 22 on the side surface of the element body 10 by dipping or the like.

  According to the power inductor 2 according to the present embodiment, the number of turns of the coil can be increased as compared with the power inductor 1 according to the first embodiment, so that the inductance value can be improved. Other operations and effects are the same as those in the first embodiment.

  In the present embodiment, among the coil conductors 33, 34, 35, and 36, the coil conductors 33 and 34 located on the outer layer side have a structure embedded in the third insulator 61, but are shown in FIG. It may be embedded in the second insulator 51 like the power inductor 2 ′.

  Although the embodiment of the present invention has been described in detail above, the present invention is not limited to this. For example, in each of the above embodiments, a closed magnetic circuit in which through holes are formed in the first insulator and the second insulator on the inner peripheral side and the outer peripheral side of the coil, and the third insulator is filled in the through holes. Although it is a type inductor, it may be a disclosed path type inductor by omitting the formation of the through hole and the filling of the third insulator.

  In the above embodiment, the combination of the magnetic permeability of the first insulator 41, the magnetic permeability of the second insulator 51, and the magnetic permeability of the third insulator 61 is “high / high / high”, “ Although “1 (nonmagnetic) · high / high” and “1 (nonmagnetic) · 1 (nonmagnetic) · high” are illustrated, other combinations may be used. For example, the combinations include “low / high / high”, “low / low / high”, and “1 (non-magnetic) / low / high”. What kind of combination should be adopted may be appropriately selected according to product specifications and the like.

  Further, in the first embodiment, the interlayer connection of the coil conductor is performed using the inner peripheral surface of the through hole formed inside the coil in order to fill the third insulator. In addition to the hole, the conductive connection may be made via an interlayer connection via.

  Moreover, in the said embodiment, although the terminal electrode was formed in the both ends of an element | base_body, you may make it form in any one or both, or a side surface of an upper surface or a lower surface according to product specifications etc.

  In each of the above embodiments, the power inductor in which one circuit coil is embedded has been described. However, the present invention can also be applied to an inductor array in which multiple circuit coils are embedded.

External perspective view of power inductor Cross section of power inductor Disassembled perspective view of power inductor body Diagram explaining the manufacturing method of power inductor Diagram explaining the manufacturing method of power inductor Cross section of power inductor Disassembled perspective view of power inductor body Diagram explaining the manufacturing method of power inductor Cross section of power inductor

Explanation of symbols

  1, 2, 2 '... power inductor, 10 ... element body, 21, 22 ... terminal electrode, 31-36 ... coil conductor, 41 ... first insulator, 51 ... second insulator, 61 ... third Insulator, 71 ... through hole, 72 ... through hole, 74,75 ... via

Claims (7)

In a power inductor in which a coil conductor is embedded and a terminal electrode connected to the coil conductor is formed on the outer surface of the element,
The element body includes a first insulator, a coil conductor formed on an upper surface and a lower surface of the first insulator, and a second insulator formed so as to cover the coil conductor and the first insulator. And a third insulator formed to cover at least the upper and lower surfaces of the second insulator,
The power inductor is characterized in that at least the third insulator is made of an organic resin containing a flat metal-based soft magnetic powder as a filler. 2. The power inductor according to claim 1, wherein the second insulator is made of an organic resin containing a flat metallic soft magnetic powder as a filler. 3. The power inductor according to claim 1, wherein the first insulator is made of an organic resin containing a flat metal-based soft magnetic powder as a filler. 4. The magnetic permeability of the third magnetic body is greater than or equal to the permeability of the second magnetic body, and the permeability of the second magnetic body is greater than or equal to the permeability of the first magnetic body. The power inductor according to any one of 1 to 3. The power inductor according to any one of claims 1 to 4, wherein the aspect ratio of the metallic soft magnetic powder is 10 or more. The third magnetic body is formed in the inner peripheral portion and the outer peripheral portion of the coil conductor so as to penetrate the first magnetic body and the second magnetic body. 1. Power inductor according to item 1 The power inductor according to any one of claims 1 to 6, wherein the coil conductor is formed in multiple layers.

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