Coil component

A coil component includes a support substrate and a coil portion disposed on the support substrate, a body in which the support substrate and the coil portion are embedded, first and second lead portions extending from the coil portion and respectively exposed to a surface of the body, a surface insulating layer disposed on the surface of the body and having openings respectively exposing the first and second lead portions, and first and second external electrodes disposed on the surface insulating layer and connected to the first and second lead portions exposed through the openings. Each of the first and second external electrodes includes a first metal layer formed of a metal and in direct contact with the first and second lead portions.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims benefit under 35 USC 119(a) of Korean Patent Application No. 10-2019-0173853 filed on Dec. 24, 2019 in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference for all purposes.

TECHNICAL FIELD

The present disclosure relates to a coil component.

BACKGROUND

Inductors, as coil components, are typical passive elements constituting electronic circuits together with resistors and capacitors to remove noise.

A thin-film coil component is manufactured by forming a coil portion by plating, and then curing a magnetic powder-resin composite in which the magnetic powder and resin are mixed to produce a body, and forming an external electrode on the outside of the body.

However, when the body is manufactured using the magnetic metal powder and the external electrode is formed by plating on the outside of the body, parasitic capacitance may occur between the coil portion and the external electrode.

Therefore, it is necessary to improve the characteristics of the component by disposing an insulating layer on the surface of the body and adjusting the distance between the coil portion and the external electrode or the contact area between the body and the external electrode.

SUMMARY

An aspect of the present disclosure is to provide a coil component in which parasitic capacitance may be reduced by adjusting a distance between a coil portion and an external electrode or an area of contact between a body and an external electrode.

An aspect of the present disclosure is to provide a coil component in which the reduction in a magnetic substance volume of a body may be effectively prevented.

According to an aspect of the present disclosure, a coil component includes a support substrate and a coil portion disposed on the support substrate, a body in which the support substrate and the coil portion are embedded, first and second lead portions extending from the coil portion and respectively exposed to a surface of the body, a surface insulating layer disposed on the surface of the body and having openings respectively exposing the first and second lead portions, and first and second external electrodes disposed on the surface insulating layer and connected to the first and second lead portions exposed through the opening. Each of the first and second external electrodes includes a first metal layer formed of a metal and in direct contact with the first and second lead portions.

DETAILED DESCRIPTION

The drawings may not be to scale, and the relative size, proportions, and depiction of elements in the drawings may be exaggerated for clarity, illustration, and convenience.

A value used to describe a parameter such as a 1-D dimension of an element including, but not limited to, “length,” “width,” “thickness,” diameter,” “distance,” “gap,” and/or “size,” a 2-D dimension of an element including, but not limited to, “area” and/or “size,” a 3-D dimension of an element including, but not limited to, “volume” and/or “size”, and a property of an element including, not limited to, “roughness,” “density,” “weight,” “weight ratio,” and/or “molar ratio” may be obtained by the method(s) and/or the tool(s) described in the present disclosure. The present disclosure, however, is not limited thereto. Other methods and/or tools appreciated by one of ordinary skill in the art, even if not described in the present disclosure, may also be used.

In the drawings, the X direction may be defined as a first direction or a longitudinal direction, a Y direction as a second direction or a width direction, and a Z direction as a third direction or a thickness direction.

Hereinafter, a coil component according to an exemplary embodiment will be described in detail with reference to the accompanying drawings, and in describing with reference to the accompanying drawings, the same or corresponding components are assigned the same reference numbers, and overlapped descriptions thereof will be omitted.

Various types of electronic components are used in electronic devices, and various types of coil components may be appropriately used to remove noise between the electronic components.

For example, in electronic devices, coil components may be used as power inductors, high-frequency (HF) inductors, general beads, high-frequency beads (GHz Beads), and common mode filters.

Hereinafter, exemplary embodiments will be described on the premise that a coil component according to an exemplary embodiment is a power inductor used in a power line of a power supply circuit. However, the coil component according to an exemplary embodiment may be suitably applied as a chip bead, a chip filter, or the like as well as a power inductor.

First Embodiment

FIG.1is a view schematically illustrating a coil component according to a first embodiment.FIG.2is a view schematically illustrating the arrangement structure of a surface insulating layer and an external electrode formed in the coil component ofFIG.1.FIG.3is a view illustrating a cross section taken along line I-I′ ofFIG.1.FIG.4is a view illustrating a cross section taken along line II-II′ ofFIG.1.

FIG.1mainly illustrates a body applied to a coil component according to the first embodiment, andFIG.2mainly illustrates a surface insulating layer and an external electrode applied to the coil component according to the first embodiment.

Referring toFIGS.1to4, a coil component1000according to the first embodiment includes a body100, a support substrate200, first and second coil portions310and320, and first and second lead portions410and420, a surface insulating layer500, first and second external electrodes610and620, and first and second auxiliary lead portions810and820.

The body100forms the exterior of the coil component1000according to the embodiment, and includes the support substrate200and the coil portions310and320embedded therein to be described later.

The body100may be formed to have a hexahedral shape as a whole.

Based onFIG.1, the body100includes a first surface101and a second surface102opposing each other in the X direction, a third surface103and a fourth surface104opposing each other in the Z direction, and a fifth surface105and a sixth surface106opposing each other in the Y direction. The first surface101and the second surface102of the body100opposing each other respectively connect the third surface103and the fourth surface104of the body100opposing each other. The fifth surface105and the sixth surface106of the body100opposing each other respectively connect the first surface101and the second surface102of the body100opposing each other. In this embodiment, one surface and the other surface of the body100refer to the third surface103and the fourth surface104, respectively, one side and the other side refer to the first surface101and the second surface102, respectively, and one end and the other end refers to the fifth surface105and the sixth surface106, respectively.

The body100may be configured, for example, in such a manner that the coil component1000according to this embodiment, in which the external electrodes610and620to be described later are formed, has a length of 2.0 mm, a width of 1.2 mm and a thickness of 0.8 mm or less, or a length of 1.6 mm, a width of 0.8 mm and a thickness of 0.8 mm or less, or a length of 0.2 mm, a width of 0.25 mm and a thickness of 0.4 mm, but the configuration is not limited thereto. On the other hand, since the above-described numerical values do not take into account the error in the process, it is also within the scope of the present invention to have a numerical value different from the above-mentioned value due to the process error.

The length, width, and thickness of the coil component1000described above may be measured by micrometer measurement, respectively. The micrometer measurement method is measured by setting the zero point with a micrometer (apparatus) which is gage R&R (Repeatability and Reproducibility), inserting the coil part1000between the tips of the micrometer, and turning the micrometer's measuring lever. On the other hand, in measuring the length of the coil component1000by using a micrometer measurement method, the length of the coil component1000may mean a value measured once, or may mean an arithmetic average of values measured multiple times. This may also be applied to the case of measuring the width and thickness of the coil component1000.

Alternatively, the length, width, and thickness of the coil component1000described above may be measured by a cross-section analysis method, respectively. As an example, the length of the coil part1000by the cross-section analysis method is an optical microscope for the cross-section in the longitudinal direction (X)-thickness direction (Z) in the center of the width direction (Y) of the body100. Or based on a picture of a scanning electron microscope (SEM, Scanning Electron Microscope), the length of the coil component1000may mean the maximum value of the length of a plurality of line segments parallel to the longitudinal direction (X) of the body100connecting the outermost boundary line of the coil part1000shown in the cross-sectional view. Alternatively, the length of the coil component1000may mean the minimum value of the length of a plurality of line segments parallel to the longitudinal direction (X) of the body100connecting the outermost boundary line of the coil part1000shown in the cross-sectional view. Alternatively, the length of the coil component1000may mean an arithmetic mean value of the length of a plurality of line segments parallel to the longitudinal direction (X) of the body100connecting the outermost boundary line of the coil part1000shown in the cross-sectional view. The above description can be applied to the width and thickness of the coil component1000in the same way.

The body100may include a magnetic material and a resin. In detail, the body100may be formed by laminating one or more magnetic sheets including a resin and a magnetic material dispersed in the resin. The body100may also have a structure other than the structure in which the magnetic material is dispersed in the resin. For example, the body100may be formed of a magnetic material such as ferrite.

The magnetic material may be ferrite or magnetic metal powder.

Ferrite powder particles may be at least one of, for example, spinel ferrites such as Mg—Zn, Mn—Zn, Mn—Mg, Cu—Zn, Mg—Mn—Sr, Ni—Zn and the like, hexagonal ferrites such as Ba—Zn, Ba—Mg, Ba—Ni, Ba—Co, Ba—Ni—Co and the like, garnet ferrites such as Y, and Li ferrites.

The magnetic metal powder may be amorphous or crystalline. For example, the magnetic metal powder may be Fe—Si—B—Cr-based amorphous alloy powder, but is not limited thereto.

The ferrite power and the magnetic metal powder may have an average diameter of about 0.1 μm to 30 μm, respectively, but the diameters thereof are not limited thereto.

The body100may include two or more types of magnetic materials dispersed in a resin. In this case, the fact that the magnetic materials are different types means that the magnetic materials dispersed in the resin are distinguished from each other by any one of an average diameter, a composition, crystallinity, and a shape.

The resin may include an epoxy, polyimide, a liquid crystal polymer, or the like, alone or in combination, but the embodiment is not limited thereto.

The body100includes a core110penetrating through the first and second coil portions310and320and the support substrate200to be described later. The core110may be formed by filling through-holes of the first and second coil portions310and320with the magnetic composite sheet, but the embodiment is not limited thereto.

The support substrate200is embedded inside the body100, and includes one surface and the other surface opposing each other. In this embodiment, one surface of the support substrate200refers to a lower surface of the support substrate200, and the other surface of the support substrate200refers to an upper surface of the support substrate200.

The thickness of the support substrate200may be 10 μm or more and 60 μm or less.

The support substrate200is formed of an insulating material including a thermosetting insulating resin such as an epoxy resin, a thermoplastic insulating resin such as polyimide, or a photoimageable dielectric resin, or may be formed of an insulating material in which a reinforcing material such as glass fiber or filler is impregnated in such an insulating resin. As an example, the support substrate200may be formed of an insulating material such as prepreg, Ajinomoto Build-up Film (ABF), FR-4, bismaleimide triazine (BT) film, or Photoimageable Dielectric (PID) film, but the present disclosure is not limited thereto.

As the filler, at least one or more selected from the group consisting of silica (SiO2), alumina (Al2O3), silicon carbide (SiC), barium sulfate (BaSO4), talc, mud, mica powder, aluminum hydroxide (Al(OH)3), magnesium hydroxide (Mg(OH)2), calcium carbonate (CaCO3), magnesium carbonate (MgCO3), magnesium oxide (MgO), boron nitride (BN), aluminum borate (AlBO3), barium titanate (BaTiO3) and calcium zirconate (CaZrO3).

When the support substrate200is formed of an insulating material including a reinforcing material, the support substrate200may provide relatively superior rigidity. When the support substrate200is formed of an insulating material that does not contain glass fiber, the support substrate200is advantageous in terms of reducing the overall thickness of the coil portions310and320. When the support substrate200is formed of an insulating material including a photoimageable dielectric resin, the number of processes of forming the coil portions310and320may be reduced, which is advantageous in reducing production costs and in forming a fine via.

The first and second coil portions310and320are disposed on one surface and the other surface opposing each other, respectively, on the support substrate200and exhibit characteristics of the coil component. For example, when the coil component1000of this embodiment is used as a power inductor, the electric field of the coil portions310and320may be stored as a magnetic field to maintain an output voltage, thereby stabilizing power of electronic devices.

Referring toFIGS.1to4, each of the first coil portion310and the second coil portion320may be in the form of a flat spiral formed with at least one turn with respect to the core110as an axis. For example, the first coil portion310may form at least one turn about the core110as an axis, on one surface of the support substrate200.

The first and second coil portions310and320may include a coil pattern of a flat spiral shape, and the first and second coil portions310and320disposed on both surfaces of the support substrate200opposing each other may be electrically connected through a via electrode900formed in the support substrate200.

The first and second coil portions310and320and the via electrode900may be formed to include a metal having excellent electrical conductivity, and for example, may be formed of silver (Ag), palladium (Pd), aluminum (Al), nickel (Ni), titanium (Ti), gold (Au), copper (Cu), platinum (Pt), or alloys thereof.

The first and second lead portions410and420extend from the first and second coil portions310and320and are exposed to the first surface101and the second surface102of the body100, respectively. Referring toFIGS.1to3, one end of the first coil portion310is extended on one surface of the support substrate200to form the first lead portion410, and the first lead portion410is exposed to the first surface101of the body100. In addition, one end of the second coil portion320is extended on the other surface of the support substrate200to form the second lead portion420, and the second lead portion420is exposed to the second surface102of the body100.

The first and second auxiliary lead portions810and820may be disposed to correspond to the first and second lead portions410and420, on the other surface and one surface of the support substrate200, respectively. The first lead portion410is disposed on one surface of the support substrate200, and the first auxiliary lead portion810is disposed on the other surface of the support substrate200. The second lead portion420is disposed on the other surface of the support substrate200, and the second auxiliary lead portion820is disposed on one surface of the support substrate200. Although not illustrated in detail, a connection via (not illustrated) connecting the first lead portion410and the first auxiliary lead portion810, and a connecting via (not illustrated) connecting the second lead portion420and the second auxiliary lead portion820may be formed respectively. As a result, the first lead portion410and the first auxiliary lead portion810may be electrically connected to each other, and the second lead portion420and the second auxiliary lead portion820may be electrically connected to each other.

The first auxiliary lead portion810is disposed to correspond to the first lead portion410based on the support substrate200, and the second auxiliary lead portion820is disposed to correspond to the second lead portion420, based on the support substrate200. On the other hand, the first and second auxiliary lead portions810and820may be exposed to the surface of the body100together with the first and second lead portions410and420. Accordingly, the first and second external electrodes610and620are formed not only on the exposed surfaces of the first and second lead portions410and420, but also on the exposed surfaces of the first and second auxiliary lead portions810and820. Although not illustrated in detail, since the bonding force between the surface insulating layer500and the metal is weaker than the bonding force between the surface insulating layer500and the body100, the opening P, which will be described later, may also be formed on the exposed surfaces of the first and second auxiliary lead portions810and820. Therefore, of the surface of the body100, the area of a region thereof in which the first and second external electrodes610and620may be metal-bonded increases, thereby increasing the bonding force between the body100and the first and second external electrodes610and620.

At least one of the coil portions310and320, the via electrode900, the lead portions410and420, and the auxiliary lead portions810and820may include at least one or more conductive layers.

For example, when the first coil portion310, the first lead portion410, the first auxiliary lead portion810and the via electrode900are formed by plating on one surface side of the support substrate200, the first coil portion310, the first lead portion410, the first auxiliary lead portion810, and the via electrode900may each include a seed layer such as an electroless plating layer or the like, and an electroplating layer. In this case, the electroplating layer may have a single layer structure or a multilayer structure. The multilayer electroplating layer may be formed of a conformal film structure in which one electroplating layer is covered by the other electroplating layer, or may be formed to have a shape in which the other electroplating layer is laminated only on one surface of one electroplating layer. In the above-described example, the seed layer of the first coil portion310, the seed layer of the first lead portion410, the seed layer of the first auxiliary lead portion810and the seed layer of the via electrode900may be integrally formed, so that a boundary therebetween is not formed, but the embodiment is not limited thereto. In addition, in the above-described example, the electroplating layer of the first coil portion310, the electroplating layer of the first lead portion410, the electroplating layer of the first auxiliary lead portion810and the electroplating layer of the via electrode900may be integrally formed, so that a boundary therebetween is not formed, but the embodiment is not limited thereto.

The coil portions310and320, the lead portions410and420, the auxiliary lead portions810and820, and the via electrode900, respectively, may be formed of a conductive material such as copper (Cu), aluminum (Al), silver (Ag), tin (Sn), gold (Au), nickel (Ni), lead (Pb), titanium (Ti), or alloys thereof, but the embodiment is not limited thereto.

The surface insulating layer500is disposed on the surface of the body100and has an opening P exposing the first and second lead portions410and420. The opening P refers to a region in the first and second surfaces101and102of the body100, in which the first and second lead portions410and420are exposed.

Referring toFIGS.1to3, the surface insulating layer500includes a first surface insulating layer510formed on a region of the body100except for regions in which the first and second lead portions410and420are exposed among the first and second surfaces101and102of the body100, and a second surface insulating layer520disposed on the third surface103and the fourth surface104, and the fifth surface105and the sixth surface106, of the body100.

Referring toFIG.3, the second surface insulating layer520is formed to reach both ends of the body100, opposing each other in the longitudinal direction X, respectively from the third surface103, the fourth surface104, the fifth surface105, and the sixth surface106of the body100.

The surface insulating layer500may be formed of an insulating material. As an example, the insulating material may be a thermosetting resin such as an epoxy resin, a thermoplastic resin such as polyimide, a photoimageable resin, or a liquid crystal crystalline polymer (LCP), but the material is not limited thereto. For example, the surface insulating layer500may be formed as a plating resist for the plating of the first and second external electrodes610and620to be described later. In addition, the surface insulating layer500may be formed by applying or printing such an insulating material on the surface of the body100. Therefore, the surface insulating layer500may be formed in a region of the surface of the body100except for regions in which the first and second lead portions410and420are exposed. On the other hand, the surface insulating layer500may be formed of a thin parylene film, or may be formed using various insulating materials such as a silicon oxide film (SiO2), a silicon nitride film (Si3N4), and a silicon oxynitride film (SiON). When the insulating layer500is formed using these materials, various methods such as vapor deposition or the like may be used. Thus, the surface insulating layer500may be disposed to continuously cover the magnetic metal powder particles and the resin of the body100, on the surface of the body100.

Recently, as the mobile communication speed has increased, the driving frequency of coil components used in mobile devices has also tended to increase. To smoothly use the coil component in the high frequency region, there is a need to reduce the parasitic capacitance in the coil component. On the other hand, the shorter the separation distance between the coil portions310and320and the external electrodes610and620is, the larger the contact area between the body100and the external electrodes610and620is, the parasitic capacitance in the coil component increases. In this embodiment, by forming the surface insulating layer500on the surface of the body100, the separation distance between the coil portions310and320and the external electrodes610and620is increased to significantly reduce parasitic capacitance occurring between the coil portions310and320and the external electrodes610and620.

The first and second external electrodes610and620are disposed on the surface of the body100to cover the first and second lead portions410and420. For example, the first and second external electrodes610and620are disposed on the surface insulating layer500and are connected to the first and second lead portions410and420exposed through the opening P, respectively.

Referring toFIGS.1to3, since the first lead portion410is exposed to the first surface101of the body100, the first external electrode610may be formed on the first surface101of the body100to contact the first lead portion410. Since the second lead portion420is exposed to the second surface102of the body100, the second external electrode620may be formed on the second surface102of the body100to contact the second lead portion420. Although not illustrated in detail, the width of each of the first and second external electrodes610and620may be less than the width of the body100. As described above, the parasitic capacitance in the coil component1000increases as the area of contact between the body100and the external electrodes610and620increases. In this embodiment, by reducing the contact area between the body100and the external electrodes610and620on the first and second surfaces101and102, the parasitic capacitance occurring between the body100and the external electrodes610and620may be significantly reduced.

Referring toFIG.3, the first and second external electrodes610and620include first metal layers611and621directly contacting the first and second lead portions410and420and filling the opening P, respectively. Since the first metal layers611and621are formed by plating directly on the surface insulating layer500, the first metal layers611and621are formed of a metal. The first metal layers611and621may be copper (Cu) metal layers having excellent electrical conductivity and low material costs, but the embodiment is not limited thereto. On the other hand, the first metal layers611and621are formed by plating, and thus, may not contain a glass component or a resin. In the case in which the body100is generally manufactured by curing the magnetic metal powder-resin composite, the external electrodes610and620may be formed using a conductive resin paste containing a conductive metal and a resin. In this case, as the conductive metal contained in the conductive resin paste, silver (Ag) having a low specific resistance is mainly used, but silver (Ag) has a high material cost as well as frequent contact failures with the coil portions310and320, and thus, excessive contact resistance may rise. Therefore, in the case of this embodiment of the present disclosure, since the first metal layers611and621are directly formed on the surface insulating layer500, contact failure between the coil portions310and320and the external electrodes610and620may be prevented. In addition, in the case in which the external electrodes610and620are formed using the conductive resin paste, adjusting the coating thickness of the conductive resin paste is difficult, and thus, the external electrodes610and620may be formed thick, causing a problem such as reduction in the volume of the body100thereby. However, in this embodiment of the present disclosure, since the external electrodes610and620are formed by plating a metal on the surface of the body100, the thickness of the external electrodes610and620may be adjusted to be relatively thinner. Accordingly, the volume of the body100may be increased, and inductance characteristics of the entirety of the component may be improved.

Referring toFIG.3, the first and second external electrodes610and620further include first and second conductive resin layers612and622disposed on the third surface103or the fourth surface104of the body100and formed between the second surface insulating layer520and the first metal layers611and621, respectively. The first and second conductive resin layers612and622may include any one or more conductive metals selected from the group consisting of copper (Cu), nickel (Ni), and silver (Ag), and a thermosetting resin. The first and second conductive resin layers612and622are formed by applying and curing a conductive paste containing a conductive metal such as silver (Ag) and a resin. Referring toFIG.3, the first and second conductive resin layers612and622are disposed on the third surface103or the fourth surface104of the body100to be disposed between the second surface insulating layer520and the first metal layers611and621. Although not illustrated in detail, by forming the above-described surface insulating layer500on the third surface103or the fourth surface104of the body100with a plating resist, the first metal layers611and621may cover only portions of the first and second conductive resin layers612and622. By using the thermosetting resin included in the first and second conductive resin layers612and622and the body100with the same thermosetting resin, for example, an epoxy resin, bonding strength between the body100and the external electrodes610and620may be improved. Among the first surface101, the third surface103, and the fourth surface104, the first conductive resin layer612is disposed only on the third surface103, or the fourth surface104, or both the third and fourth surfaces103and104. Among the second surface101, the third surface103, and the fourth surface104, the second conductive resin layer622is disposed only on the third surface103, or the fourth surface104, or both the third and fourth surfaces103and104.

The first and second external electrodes610and620further include second metal layers613and623disposed on the first metal layers611and621and formed of a different metal from that of the first metal layers611and621. The second metal layers613and623may include sequentially a first layer (not illustrated) containing nickel (Ni) or a second layer (not illustrated) including tin (Sn). The second layer (not illustrated), which is an outermost layer of the first and second external electrodes610and620, is formed of a tin (Sn) plating layer, thereby improving bonding force with solder when mounting the coil component1000on a printed circuit board. In addition, by forming the first layer (not illustrated) as a nickel (Ni) plating layer, the connectivity between the first metal layers611and621formed of a copper (Cu) plating layer and the second layer (not illustrated) formed of a tin (Sn) plating layer may be improved.

Second Embodiment

FIG.5is a view schematically illustrating a coil component according to a second embodiment.FIG.6is a view schematically illustrating the arrangement structure of a surface insulating layer, an external electrode, and an additional insulating layer formed in the coil component ofFIG.5.FIG.7is a view illustrating a cross section taken along line III-III′ ofFIG.5.

FIG.5mainly illustrates a body applied to the coil component according to the second embodiment, andFIG.6mainly illustrates a surface insulating layer, an external electrode, and an additional insulating layer applied to the coil component according to the second embodiment.

Compared to the coil component1000according to the first embodiment, the presence or absence of an additional insulating layer700is different in a coil component2000according to this embodiment. Therefore, in describing this embodiment, only the additional insulating layer700different from the first embodiment will be described. The rest of the configuration of this embodiment may be applied as described in the first embodiment.

Referring toFIGS.5and7, the coil component2000of this embodiment further includes the additional insulating layer700disposed on the first metal layers611and621. The additional insulating layer700is interposed between the first metal layers611and621and the second metal layers612and622. The width of the additional insulating layer700in the Y direction may be substantially the same as the width of the body100in the Y direction. As described above, the parasitic capacitance in the coil component increases as the separation distance between the coil portions310and320and the external electrodes610and620is relatively shorter. In this embodiment, by further disposing the additional insulating layer700on the first surface101and the second surface102of the body100, the separation distance between the coil portion310and320and the external electrodes610and620may increase, thereby significantly reducing parasitic capacitance occurring between the coil portions310and320and the external electrodes610and620. To ensure a connection between the first metal layer611and the second metal layers613and a connection between the first metal layer621and the second metal layers623, the additional insulating layer700may not be disposed on the first surface101and the second surface102.

As set forth above, according to an exemplary embodiment, parasitic capacitance may be reduced by adjusting a distance between a coil portion and an external electrode or an area of contact between a body and an external electrode.

In addition, according to an exemplary embodiment, the reduction in the volume of a magnetic substance of a body may be effectively prevented.