Patent Publication Number: US-2016225511-A1

Title: Power inductor

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of priority to Korean Patent Application No. 10-2015-0015298, filed on Jan. 30, 2015 with the Korean Intellectual Property Office, the entirety of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to a power inductor. 
     BACKGROUND 
     An inductor is one of the important passive elements which form an electronic circuit along with a resistor and a capacitor, and is used as a component for removing noise or forming an LC resonant circuit. 
     An inductor may be classified into a wound-type, a multilayer-type, a thin film-type, and the like, depending on its structure, and is generally manufactured by printing a conductive pattern on an insulation layer to form a coil, which is stacked into a plurality of layers and then subjected to pressing and sintering. 
     Recently, as the manufacturing of miniaturized and high-performance electronic devices has been developed, essential electronic components mounted in electronic devices further require higher frequency and higher current, along with miniaturization. 
     Among such structures, a thin film-type inductor may be formed of a material having a high saturation magnetization value, and even in the case of being manufactured in a compact size, it may be easy to form an internal circuit pattern as compared with a multilayer-type inductor. Therefore, recently, research into thin film-type inductors has been actively conducted. 
     SUMMARY 
     An aspect of the present disclosure provides a power conductor having a novel structure capable of property improvement. 
     Since it is difficult to further satisfy the properties of the inductor to be miniaturized and have a high degree of inductance due to its material limitation or structural limitation, the aspect of the power inductor according to the present disclosure was devised in order to overcome the material and structural limitations. 
     For this, the present disclosure provides a power inductor capable of utilizing shape anisotropy possessed by flake alloy powder. 
     According to an aspect of the present disclosure, a power inductor comprises: a magnetic body; a coil provided in the magnetic body; and external electrodes disposed on the magnetic body. The magnetic body comprises a stacked plurality of magnetic sheets including a flake alloy powder, and a major axis of the flake alloy powder and a major axis of the coil are arranged in a direction parallel to an upper surface of the magnetic body. 
     The major axis of the flake alloy powder maybe parallel to a direction of a magnetic flux generated in the coil. 
     The coil may include: a first wiring pattern formed in an upper magnetic sheet among the plurality of magnetic sheets, a second wiring pattern formed in a lower magnetic sheet among the plurality of magnetic sheets, a plurality of layers of vias formed in a plurality of magnetic sheets among the plurality of magnetic sheets, and electrically connecting the first and second wiring patterns, and lead patterns formed in the lower magnetic sheet, and connected to the external electrodes. 
     The lead patterns may be formed on a same plane as the second wiring pattern. 
     At least anyone of the vias, the first and second wiring patterns, and the lead patterns may include a plated layer. 
     The flake alloy powder may include iron (Fe). 
     The flake alloy powder may be one or more selected from the group consisting of an Fe—Si-based alloy, sendust (Fe—Si—Al), permalloy (Fe—Ni), an Fe—Si—Cr-based alloy, and an Fe—Si—B—Cr-based amorphous alloy. 
     The magnetic sheet may have a thickness of 30 μm to 90 μm. 
     The magnetic body may include an outer magnetic sheet provided on an outermost layer, the outer magnetic sheet covering the coil and having no pattern. 
     The magnetic sheet may include a binder. 
     The external electrodes may be formed at opposite end portions of the magnetic body. 
     According to another aspect of the present disclosure, a power inductor comprises : a magnetic body comprising a stacked plurality of magnetic sheets; a coil provided in the magnetic body; and external electrodes disposed on the magnetic body. The coil includes a plurality of layers of vias, the plurality of layers of vias comprising vias formed in each magnetic sheet into a plurality of layers. 
     According to another aspect of the present disclosure, a power inductor comprises: a magnetic body; a coil provided in the magnetic body; and external electrodes disposed on the magnetic body. The magnetic body comprises a stacked plurality of magnetic sheets, and uppermost and lowermost magnetic sheets among the plurality of magnetic sheets include a flake alloy powder, and a major axis of the flake alloy powder and a major axis of the coil are arranged in a direction parallel to an upper surface of the magnetic body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other aspects, features, and advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a power inductor according to an exemplary embodiment in the present disclosure; 
         FIG. 2  is a cross-sectional view taken along line I-I′ of  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of a magnetic sheet used in the power inductor of the present disclosure; 
         FIG. 4  is a partially exploded perspective view of a magnetic body of  FIG. 1 ; 
         FIG. 5  is an enlarged perspective view of a coil formed within the magnetic body of  FIG. 1 ; and 
         FIG. 6  is a cross-sectional view of a power inductor according to another exemplary embodiment in the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments of the present inventive concept will be described as follows with reference to the attached drawings. 
     The present inventive concept may, however, be exemplified in many different forms and should not be construed as being limited to the specific embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. 
     Throughout the specification, it will be understood that when an element, such as a layer, region or wafer (substrate), is referred to as being “on,” “connected to,” or “coupled to” another element, it can be directly “on,” “connected to,” or “coupled to” the other element or other elements intervening therebetween may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to,” or “directly coupled to” another element, there may be no elements or layers intervening therebetween. Like numerals refer to like elements throughout. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be apparent that though the terms first, second, third, etc. may be used herein to describe various members, components, regions, layers and/or sections, these members, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one member, component, region, layer or section from another region, layer or section. Thus, a first member, component, region, layer or section discussed below could be termed a second member, component, region, layer or section without departing from the teachings of the exemplary embodiments. 
     Spatially relative terms, such as “above,” “upper,” “below,” and “lower” and the like, may be used herein for ease of description to describe one element&#39;s relationship to another element(s) as shown in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “upper,” or “above” other elements would then be oriented “lower,” or “below” the other elements or features. Thus, the term “above” can encompass both the above and below orientations depending on a particular direction of the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may be interpreted accordingly. 
     The terminology used herein is for describing particular embodiments only and is not intended to be limiting of the present inventive concept. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” and/or “comprising” when used in this specification, specify the presence of stated features, integers, steps, operations, members, elements, and/or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, members, elements, and/or groups thereof. 
     Hereinafter, embodiments of the present inventive concept will be described with reference to schematic views illustrating embodiments of the present inventive concept. In the drawings, for example, due to manufacturing techniques and/or tolerances, modifications of the shape shown may be estimated. Thus, embodiments of the present inventive concept should not be construed as being limited to the particular shapes of regions shown herein, for example, to include a change in shape results in manufacturing. The following embodiments may also be constituted by one or a combination thereof. 
     The contents of the present inventive concept described below may have a variety of configurations and propose only a required configuration herein, but are not limited thereto. 
       FIG. 1  is a perspective view of a power inductor according to an exemplary embodiment,  FIG. 2  is a cross-sectional view taken along line I-I′ of  FIG. 1 ,  FIG. 3  is a cross-sectional view of a magnetic sheet used in the power inductor of the present disclosure,  FIG. 4  is a partially exploded perspective view of a magnetic body of  FIG. 1 , and  FIG. 5  is an enlarged perspective view of a coil formed within the magnetic body of  FIG. 1 . 
     As illustrated in  FIGS. 1 to 5 , the power inductor  100  of the exemplary embodiment includes a magnetic body  120 , a coil  130  provided in the magnetic body  120 , and external electrodes  140  formed at opposite end portions of the magnetic body  120 . 
     Referring to  FIGS. 2 and 3 , the magnetic body  120  may be manufactured by stacking and then pressing a plurality of plate magnetic sheets  110  formed of magnetic materials. In  FIG. 2 , the magnetic body  120  is illustrated integrally without distinction of each magnetic sheet  110  in an area in which the coil (see  130  in  FIG. 5 ) is formed, except for the magnetic sheet disposed at an outermost layer. 
     First, referring to  FIG. 3 , each magnetic sheet  110  used in the exemplary embodiment and forming the magnetic body  120  is formed by filling a binder  114  with flake alloy powder  112 . 
     This flake alloy powder  112  is shape anisotropic powder having a major axis L and a minor axis S, and the major axis L of the flake alloy powder may be arranged in a direction parallel to an upper surface of the magnetic sheet  110 . 
     The flake alloy powder  112  may be formed by including magnetic metal powder having little reduction in inductance by magnetic saturation, and an excellent direct current bias characteristic, such as iron (Fe). 
     Since magnetic metal materials generally have a relatively high saturation magnetization value (Ms) and small magnetic flux density variation depending on DC-bias, and thus represent small reduction in inductance depending on DC-bias, they are easily usable even at a high current. 
     The flake alloy powder  112  may be formed of an Fe—Si-based alloy, sendust (Fe—Si—Al), permalloy (Fe—Ni), an Fe—Si—Cr-based alloy, an Fe—Si—B—Cr-based amorphous alloy, and the like. Among them, one selected therefrom may be used alone, or a mixture of two or more selected therefrom may be used. 
     In order to utilize a large amount of the flake alloy powder  112 , the binder  114  is filled with the flake alloy powder  112 . As the binder  114 , any known material may be employed without limitation, and for example, a resin component such as an epoxy resin may be employed. 
     A content ratio of the flake alloy powder  112  in each magnetic sheet  110  may be varied with inductance by frequency and a Q (quality factor) property of a chip, and a content of about 70 wt % to 98 wt % based on a total weight of the magnetic sheet  110  may be employed in view of high frequency and a high degree of inductance. 
     When the content of the flake alloy powder  112  is less than 70 wt %, the content of a magnetic body is too small, and thus it may be difficult to implement a high degree of inductance, whereas when the content of the flake alloy powder  112  is more than 98 wt %, eddy-current loss may be increased in a high frequency area, and sheet molding may be difficult due to a lack of content of the resin. 
     Further, as the thickness of each magnetic sheet  110  is reduced, the effect of increasing a density of the flake alloy powder  112  within the inductor after stacking may be generated. The increase in the density of the flake alloy powder  112  in the magnetic sheet  110  may improve the properties of the inductor, such as magnetic permeability, DC-bias property, and the like. 
     In this regard, it is preferred that the magnetic sheet  110  has a thickness of about 30 μm to 90 μm. Herein, when the magnetic sheet  110  has a thickness less than 30 μm, magnetic flux saturation may occur due to an excessive increase in metal density, whereas when the magnetic sheet  110  has a thickness of more than 90 μm, the inductance of the inductor may be decreased due to the decrease in packing density, and moldability may be deteriorated due to the thickening of the sheet. 
     The magnetic sheet  110  having such a configuration may be manufactured by preparing slurry containing the flake alloy powder  112  and the binder  114  in an organic solvent, and thereafter coating the slurry on a carrier film by a casting method such as a doctor blade method, and the like, and then carrying out drying and heat treatment at a temperature of 200° C. or less, and about 100° C.-200° C. to cure the binder  114 . Herein, the organic solvent may be removed by volatilization before drying, and the carrier film may be removed after heat treatment. 
     Again, referring to  FIGS. 2 through 5 , the magnetic body  120  in which the plurality of magnetic sheets  110  containing the flake alloy powder  112  of which the major axis is arranged in parallel to an upper surface of the magnetic body  120  are stacked includes the coil  130  therein, and the magnetic body  120  and coil  130  are included as a main body. 
     As illustrated in  FIGS. 4 and 5 , the coil  130  includes a plurality of layers of vias  132 , a plurality of wiring patterns  134  and  136 , and two lead patterns  138 . 
     In the middle layers of the plurality of magnetic sheets  110 , the vias  132  are formed by penetrating the magnetic sheet  110  of each layer in a plurality of rows on one side and on the other side. A single layer of the vias  132  formed in the magnetic sheet  110  of each layer are stacked into a plurality of layers in the magnetic body  120 , thereby forming a via laminate  133 . 
     In  FIG. 5 , the via laminate  133  consisting of 5 rows and 3 layers on one side and the other side is illustrated as an example, however, in  FIG. 2 , the via laminate  133  is illustrated integrally without distinction of the layer. 
     These vias  132  are formed by filling the via hole  131  formed on the magnetic sheet  110  in each layer with a conductive material. In view of reducing thickness, the vias  132  may be formed of a plated layer in via holes  131  by a plating method. 
     For example, the vias  132  in each layer may be formed of a plated layer by punching or drilling a predetermined area to form vias of the magnetic sheet  110  in each layer to form a plurality of rows of the via holes  131  on one and the other sides, and plating the conductive material within the via holes  131  by a plating method to form a plated layer. 
     As illustrated in  FIG. 4 , on the outside of the magnetic sheet  110  in which the vias  132  are formed, the magnetic sheet  110  on which a plurality of first wiring patterns  134  are formed may be disposed on the upper layer, and the magnetic sheet  110  on which a plurality of second wiring patterns  136  and two lead patterns  138  are formed may be disposed on the lower layer. 
     The plurality of first wiring patterns  134  may be disposed at least in parallel in a stripe shape corresponding to the vias  132  in a top layer in each row. 
     Any one of the two lead patterns  138  corresponds to the via  132  in a bottom layer at an outermost area on one side to be extended to the external electrode  140  on one side, and the other one of the two lead patterns  138  corresponds to the via  132  in a bottom layer at an outermost area on the other side to be extended to the external electrode  140  on the other side. Both ends of the lead pattern  138  may be externally exposed from the magnetic body  120  at opposite end portions. 
     The plurality of second wiring patterns  136  may be disposed at least in parallel in a stripe shape in a diagonal direction corresponding to the vias  132  on one and the other sides in neighboring rows, except the vias  132  at the outermost areas on one and the other sides corresponding to the lead patterns  138 . Herein, the second wiring patterns  136  may be formed on the same plane as the lead patterns  138  to further aim at reducing a thickness of the power inductor  100 . 
     The first and second wiring patterns  134  and  136 , the vias  132 , and the lead patterns  138  provided in each magnetic sheet  110  are formed as one coil  130  within the magnetic body  120  by stacking the plurality of magnetic sheets  110 . 
     That is, as illustrated in  FIG. 5 , the coil  130  is electrically interconnected by the first and second wiring patterns  134  and  136  in each layer, the plurality of layers of vias  132  electrically connecting the first and the second wiring patterns  134  and  136 , and the lead patterns  138  connected to the vias  132  to be extended to the external electrode  140 , thereby having a spiral shape wound at least one turn. 
     This spiral coil  130  is arranged in a direction parallel to the magnetic sheet  110  within the magnetic body  120  or the upper surface of the magnetic body  120 , identically to the major axis of the flake alloy powder (see  112  of  FIG. 3 ). 
     By this configuration, when current flows in the coil  130  in  FIG. 5 , a direction of the magnetic flux (or magnetic path) is generated in a direction parallel to the upper surface of the magnetic body  120  around the coil  130 . 
     As a result, the direction of the magnetic flux generated in the coil  130  is parallel to the major axis direction of the flake alloy powder (see  112  in  FIG. 3 ). 
     In this case, the magnetic path and the major axis direction of the flake alloy powder (see  112  in  FIG. 3 ) are consistent with each other. Thus, when applying an external magnetic field, an effect of increasing the magnetic permeability may be expected as compared with a spherical or flake alloy powder (see  112  in  FIG. 3 ) having no shape anisotropy, or unshaped powder having low shape anisotropy, by the magnetic characteristic due to shape anisotropy possessed by the flake alloy powder (see  112  in  FIG. 3 ), and through which a high degree of inductance may be implemented. 
     The vias  132 , the first and second wiring patterns  134  and  136 , and the lead patterns  138  forming the coil  130  are conductive patterns generating a magnetic field by allowing current to flow when power is applied, and may be formed of materials having excellent electrical conductivity, for example, a metal selected from the group consisting of gold (Au), silver (Ag), platinum (Pt), copper (Cu), nickel (Ni), palladium (Pd), aluminum (Al), titanium (Ti), and the like, or alloys thereof, but any common conductive material may be employed without limitation. 
     The vias  132 , the first and second wiring patterns  134  and  136 , and the lead patterns  138  may be formed of the same materials for more stable electrical characteristics. 
     The plurality of first and second wiring patterns  134  and  136  and the two lead patterns  138  are formed by filling a plurality of holes (not shown) formed on the magnetic sheet  110  in each layer with conductive materials. In view of reducing thickness, at least any one of the first and the second wiring patterns  134  and  136  and the lead patterns  138  may be formed of a plated layer by a plating method, like the vias  132 . 
     For example, the first and second wiring patterns  134  and  136  and the lead patterns  138  may be formed of a plated layer by punching or drilling a predetermined area to form the first and second wiring patterns  134  and  136  and the lead patterns  138  of the magnetic sheet  110  in each layer to form holes, and plating conductive materials within the holes by a plating method. 
     For convenience of description, the vias  132  consisting of 5 rows and 3 layers are illustrated in the exemplary embodiment. The vias are not limited thereto, however, and the number of rows and layers of the vias  132  may be variously changed in consideration of the characteristics of the inductor. Further, the position of the vias  132  and the like may be changed depending on the shape change of the first and second wiring patterns  134  and  136 . 
     Further, as illustrated in  FIGS. 2 and 4 , the outermost layers, that is, the top layer and the bottom layer of the magnetic body  120  are provided with a magnetic sheet which does not include the pattern forming the coil  130 . 
     The magnetic sheets on the top and bottom layers provided in the magnetic body  120  may substantially serve as a cover covering the coil  130 . 
     When current flows in the coil  130 , a magnetic path is also formed in the magnetic sheets on the outermost layers of the magnetic body  120 . Thus, when the magnetic sheets on the outermost layers containing the flake alloy powder of which the major axis is arranged in a direction parallel to the upper surface of the magnetic body  120  are formed, magnetic flux leakage in a direction perpendicular to the major axis direction of the flake alloy powder is decreased, thereby implementing a high degree of inductance. 
     In addition, among the components of the power inductor  100 , a pair of external electrodes  140  may be formed at opposite end portions of the magnetic body  120 , as illustrated in  FIGS. 1 and 2 . 
     The external electrodes  140  may serve as external terminals electrically connecting the coil  130  and the external circuit by connection with the lead pattern  138 , which may have both ends externally exposed from the magnetic body  120 . 
     That is, as one end of the coil  130  is electrically connected to the external electrode  140  on a first side of the power inductor, and the other end of the coil  130  is electrically connected to the external electrode  140  on a second side of the power inductor, the coil  130  may be electrically connected to the external circuit via the pair of external electrodes  140 . 
     As the external electrodes  140 , any common conductive material may be employed without limitation, and for example, the external electrodes  140  may be formed of a metal selected from the group consisting of gold (Au), silver (Ag), platinum (Pt), copper (Cu), nickel (Ni), palladium (Pd), and the like, or alloys thereof. 
     The external electrodes  140  may be formed by plating the opposite end portions of the magnetic body  120  to be covered using a dipping manner and the like, and then performing sintering at a temperature of about 700° C. to 900° C. 
     As the major axis direction of the flake alloy power  112  and the direction of the magnetic flux generated in the coil  130  are consistent with each other, the thus-formed power inductor  100  may implement a high degree of inductance through increased magnetic permeability by utilizing the shape anisotropy of the flake alloy powder  112 . 
     Further, the power inductor  100  of the exemplary embodiment has a high saturation magnetization value (Ms) like the flake alloy powder, includes magnetic metal powder having a small decrease in inductance depending on DC-bias, and utilizes the shape anisotropy possessed by the flake alloy powder, thereby being usable in a high frequency band at 1 MHz or more, and at a high current. 
     Moreover, since at least any one of the vias  132 , the wiring patterns  134  and  136 , and the lead patterns  138  forming the coil  130  in the power inductor  100  of the exemplary embodiment is formed of a plated layer, the power inductor may be thinned. 
     As such, according to the exemplary embodiment, an inductance implementation problem when implementing a next-generation inductor having a smaller size than the existing inductor models may be improved through implementing high magnetic permeability utilizing the shape anisotropy of powder. Thus, a DC-bias property by decreasing the size of magnetic bodies within the inductor due to a smaller element body size may be improved. 
     Accordingly, the power inductor  100  of the exemplary embodiment is appropriate for use in a high-performance electronic device such as a smart phone, a tablet PC, and the like requiring higher frequency, higher current, higher inductance, thinning and the like. 
     Meanwhile,  FIG. 6  is a cross-sectional view of a power inductor according to another exemplary embodiment in the present disclosure. 
     In the exemplary embodiment in  FIG. 6 , the same reference numerals are assigned for the same components as in the exemplary embodiment in  FIG. 2  as previously described, and only the differences will be described while omitting overlapping description for the same components. 
     The configuration of the exemplary embodiment in  FIG. 6  is the same as that in  FIG. 2 , except that the powder contained in the magnetic sheet  110  is a spherical alloy powder  112   a  having no shape anisotropy. 
     When the horizontal structure using the plurality of layers of vias  132  illustrated in  FIG. 5  is applied to the inside of the magnetic body  120  using the spherical alloy powder  112   a , the cross-sectional area of the coil  130  to be formed may be freely increased only by adjusting the size of the via hole  131  formed on each magnetic sheet  110 . Thus, the overall efficiency of the inductor may be expected to be improved by reducing Rdc, resistance of the coil  130 , through which low current driving is possible. 
     When forming the existing coil pattern through plating by the existing manner, for reducing Rdc of the coil, it is the only way to increase the aspect ratio of the coil (the ratio of horizontal to vertical, assuming that the cross-section of the coil to be formed is rectangular) formed by plating to increase the cross-sectional area; however, in this case, it is known that implementation at about 3 to 5:1 is a technical limitation. 
     Differently from the illustration in the drawing, however, in the exemplary embodiment in  FIG. 6 , the magnetic sheets on the top and bottom layers  137  for coverage provided in the magnetic body  120  contain the flake alloy powder of which the major axis is arranged in a direction parallel to the upper surface of the magnetic body  120 , as illustrated in  FIG. 2 , and thus a high degree of inductance may be implemented due to reduction of the magnetic flux leakage, as in the exemplary embodiment of  FIG. 2 . 
     As set forth above, the power inductor according to the present exemplary embodiment may be used in a high frequency band and at a high current through improved magnetic permeability utilizing the shape anisotropy of an alloy powder, and may implement a high degree of inductance. 
     Further, the power inductor according to the exemplary embodiment may be used in a high frequency band and high current through introduction of a coil in a horizontal structure using a plurality of layers of vias within a magnetic body, and may be capable of low current driving due to Rdc reduction. 
     While exemplary embodiments have been shown and described above, it will be apparent to those skilled in the art that modifications and variations could be made without departing from the scope of the present invention as defined by the appended claims.