MULTILAYER COIL COMPONENT

A multilayer coil component includes: an element body having a pair of first side surfaces opposite to each other in a first direction and a pair of second side surfaces opposite to each other in a second direction orthogonal to the first direction; and a coil disposed inside the element body and having a coil axis extending in a third direction orthogonal to the first direction and the second direction, in which one of the pair of first side surfaces is a mounting surface, and a ratio of a first gap in the first direction between the coil and the mounting surface to a size of the element body in the first direction is 12 to 30% in a cross section viewed in the third direction.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No. 2023-163134 filed on Sep. 26, 2023, the entire contents of which are incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to a multilayer coil component.

BACKGROUND

A multilayer coil component including an element body and a coil disposed inside the element body is known (for example, Japanese Unexamined Patent Publication No. 2012-060049). In Japanese Unexamined Patent Publication No. 2012-060049, the coil has a coil axis extending in a predetermined direction. When viewed in the extending direction of the coil axis, the coil has a right-angled quadrilateral shape.

SUMMARY

The multilayer coil component having the above configuration is mounted on a mounting substrate in such an arrangement that the coil axis extends along the mounting substrate. The multilayer coil component is mounted with one side surface of the element body as a mounting surface facing the substrate. Here, when the multilayer coil component is mounted on the mounting substrate, there has been a possibility that a crack occurs in the element body due to stress applied to the mounting surface side.

An object of one aspect of the present invention is to provide a multilayer coil component capable of suppressing a crack due to stress at the time of mounting.

A multilayer coil component according to the present invention includes: an element body having a pair of first side surfaces opposite to each other in a first direction and a pair of second side surfaces opposite to each other in a second direction orthogonal to the first direction; and a coil disposed inside the element body and having a coil axis extending in a third direction orthogonal to the first direction and the second direction, in which one of the pair of first side surfaces is a mounting surface, and a ratio of a first gap in the first direction between the coil and the mounting surface to a size of the element body in the first direction is 12 to 30% in a cross section viewed in the third direction.

The multilayer coil component includes the coil disposed inside the element body and having the coil axis extending in the third direction orthogonal to the first direction and the second direction. In addition, one of the pair of first side surfaces opposite to each other in the first direction is the mounting surface. Therefore, the multilayer coil component is mounted in such an arrangement that the coil axis extends along a surface of a mounting substrate. At this time, stress is applied to the mounting surface of the multilayer coil component due to the influence of expansion, contraction, and the like of a conductor layer of the mounting substrate. On the other hand, in the cross section viewed in the third direction, the ratio of the first gap in the first direction between the coil and the mounting surface to the size of the element body in the first direction is 12 to 30%. In this case, a distance for suppressing a crack can be secured between the mounting surface, which is easily distorted by stress, and the coil in the element body. As described above, a crack due to stress at the time of mounting can be suppressed.

In the cross section viewed in the third direction, the first gap may be larger than a second gap in the second direction between the coil and the second side surfaces. In this case, a distance for suppressing a crack can be secured between the mounting surface, which is easily distorted by stress, and the coil in the element body.

The first gap may be 1.2 to 6.0 times the second gap. In this case, a distance for suppressing a crack can be secured between the mounting surface, which is easily distorted by stress, and the coil in the element body.

A surface layer region constituting the mounting surface and an internal region on the inner side of the surface layer region may be formed in a first region between the mounting surface and the coil in the element body, and the surface layer region may have a larger average crystal grain size than the internal region. In this case, the occurrence of a crack on the mounting surface can be suppressed in the surface layer region having a large average crystal grain size. On the other hand, even when a crack occurs on the mounting surface, the internal region having a small average crystal grain size and having pores can suppress the progress of the crack to the inside.

The surface layer region may be 2 to 25% of the first region. In this case, the effect of suppressing the occurrence of a crack on the mounting surface in the surface layer region and the effect of suppressing the progress of the crack in the internal region can be obtained in a well-balanced manner.

A multilayer coil component according to the present invention includes: an element body having a pair of first side surfaces opposite to each other in a first direction and a pair of second side surfaces opposite to each other in a second direction orthogonal to the first direction; and a coil disposed inside the element body and having a coil axis extending in a third direction orthogonal to the first direction and the second direction, in which one of the pair of first side surfaces is a mounting surface, and a first gap in the first direction between the coil and the mounting surface may be larger than a second gap in the second direction between the coil and the second side surface in a cross section viewed in the third direction.

The multilayer coil component includes the coil disposed inside the element body and having the coil axis extending in the third direction orthogonal to the first direction and the second direction. In addition, one of the pair of first side surfaces opposite to each other in the first direction is the mounting surface. Therefore, the multilayer coil component is mounted in such an arrangement that the coil axis extends along a surface of a mounting substrate. At this time, stress is applied to the mounting surface of the multilayer coil component due to the influence of expansion, contraction, and the like of a conductor layer of the mounting substrate. On the other hand, in the cross section viewed in the third direction, the first gap in the first direction between the coil and the mounting surface may be larger than the second gap in the second direction between the coil and the second side surface. In this case, a distance for suppressing a crack can be secured between the mounting surface, which is easily distorted by stress, and the coil in the element body. As described above, a crack due to stress at the time of mounting can be suppressed.

The first gap may be 1.2 to 6.0 times the second gap. In this case, a distance for suppressing a crack can be secured between the mounting surface, which is easily distorted by stress, and the coil in the element body.

According to the present invention, a crack due to stress at the time of mounting can be suppressed.

DETAILED DESCRIPTION

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the same or corresponding elements in the description of the drawings are denoted by the same reference signs, and redundant description is omitted.

FIG.1is a perspective view illustrating a multilayer coil component according to an embodiment.FIG.2is an exploded perspective view illustrating a layer structure of the multilayer coil component illustrated inFIG.1.FIG.3is a cross-sectional view of a mounting structure when the multilayer coil component is mounted on a mounting substrate.

As illustrated inFIG.1, a multilayer coil component1includes an element body2having a substantially rectangular parallelepiped shape and a pair of external electrodes4and5disposed at both end portions of the element body2. The element body2has, as outer surfaces, a pair of end surfaces2aand2bopposite to each other, and four side surfaces2c,2d,2e, and2fextending along a direction in which the pair of end surfaces2aand2bare opposite to each other so as to connect the pair of end surfaces2aand2b. Here, the direction in which the end surfaces2aand2bare opposite to each other is defined as a Y-axis direction (third direction). A direction in which the side surfaces2cand2dare opposite to each other is defined as a Z-axis direction (first direction). A direction in which the side surfaces2eand2fare opposite to each other is defined as an X-axis direction (second direction). The X-axis direction is a direction orthogonal to the Z-axis direction. The Y-axis direction is a direction orthogonal to the X-axis direction and the Z-axis direction. The end surface2ais disposed on the positive side in the Y-axis direction, and the end surface2bis disposed on the negative side. The side surface2cis disposed on the positive side in the Z-axis direction, and the side surface2dis disposed on the negative side. The side surface2eis disposed on the positive side in the X-axis direction, and the side surface2fis disposed on the negative side.

As illustrated inFIG.2, the element body2is formed by stacking a plurality of insulator layers11. Each of the insulator layers11has a right-angled quadrilateral shape (in the present embodiment, a rectangular shape) and has four sides11c,11d,11e, and11fthat define the side surfaces2c,2d,2e, and2f. Each of the insulator layers11is an insulator having electrical insulation properties, and is formed of a sintered body of an insulator green sheet. In the actual element body2, the insulator layers11are integrated to such an extent that boundaries between the layers cannot be visually recognized.

The size of the element body2in the Z-axis direction is defined as a dimension L1. The dimension L1is a distance between the side surfaces2cand2din the Z-axis direction. The size of the element body2in the X-axis direction is defined as a dimension L2. The dimension L2is a distance between the side surfaces2eand2fin the X-axis direction. The size of the element body2in the Y-axis direction is defined as a dimension L3(seeFIG.3). The dimension L3is a distance between the end surfaces2aand2bin the Y-axis direction. The dimension L1may be 200 μm or more, and may be 250 μm or more. In addition, the dimension L1may be 450 μm or less, and 300 μm or less. The dimension L2may be 120 μm or more, and may be 170 μm or more. In addition, the dimension L2may be 320 μm or less, and may be 210 μm or less. The dimension L3may be 250 μm or more, and may be 340 μm or more. In addition, the dimension L3may be 600 μm or less, and may be 380 μm or less. However, the dimensions are not limited to these ranges.

The external electrode4is formed so as to cover the entire one end surface2aand a part of the four side surfaces2c,2d,2e, and2f. The external electrode5is formed so as to cover the entire other end surface2band a part of the four side surfaces2c,2d,2e, and2f. The stacking direction of the plurality of insulator layers11coincides with the direction in which the pair of end surfaces2aand2bare opposite to each other. Therefore, the pair of external electrodes4and5are disposed at both end portions of the element body2in the stacking direction of the plurality of insulator layers11. The external electrode4is disposed on the positive side in the Y-axis direction. The external electrode5is disposed on the negative side in the Y-axis direction.

Each of the external electrodes4and5is formed by applying a conductive paste containing copper, silver, gold, nickel, chromium, or the like as a main component to the outer surfaces of the element body2, baking the paste, and further electroplating the outer surfaces. For electroplating, Cu, Ni, Sn, or the like can be used. The conductive paste is applied by, for example, a dipping method, a printing method, or a transfer method. The plating treatment is, for example, electrolytic plating or electroless plating. By this plating treatment, a plating layer is formed on the outer surface of the conductive paste.

As illustrated inFIG.2, the multilayer coil component1includes a plurality of coil patterns12and a connection portion13. The connection portion13includes a lead conductor14and a connection conductor15. The plurality of coil patterns12, the lead conductor14, and the connection conductor15are placed side by side in the stacking direction of the insulator layers11in the element body2. Each of the coil patterns12, the lead conductor14, and the connection conductor15include a conductive material such as copper, silver, gold, nickel, palladium, or chromium. Each of the coil patterns12, the lead conductor14, and the connection conductor15are formed as a sintered body of a conductive paste containing the conductive material. Conductor patterns to be the conductors12,14, and15are formed by screen-printing the conductive paste using screen plates in which openings corresponding to the conductor patterns are formed.

Each of the conductor patterns21forming the coil patterns12is formed in a substantially U shape. A pad portion23having a substantially circular shape and corresponding to a through-hole conductor22is formed at each of one end portion and the other end portion of the conductor pattern21. The conductor patterns21are connected in series via the through-hole conductor22in a state where the phase of the conductor pattern is shifted by 90 degrees, and form a coil10in which a coil axis L (seeFIG.3), which is a central axis, extends along the stacking direction. The coil axis L of the coil10extends in the Y-axis direction. Note that the number of windings of the coil10is not particularly limited.

A conductor pattern24forming the lead conductor14includes a pad portion (pad conductor)26having a substantially circular shape and corresponding to a through-hole conductor25. That is, the lead conductor14includes the through-hole conductor25and the pad portion26provided integrally with the through-hole conductor25. An outer end portion of the lead conductor14is exposed to the end surfaces2aand2bof the element body2in the stacking direction and connected to the external electrodes4and5. The lead conductor14is disposed at the center of the insulator layer11.

A conductor pattern27forming the connection conductor15is formed linearly so as to connect a position corresponding to one pad portion23of the coil pattern12and a position corresponding to the pad portion26of the lead conductor14. A pad portion28having a substantially circular shape and corresponding to the through-hole conductor25is formed coaxially with and substantially in the same shape as the pad portion26of the lead conductor14at one end portion of the conductor pattern27, and a pad portion29having a substantially circular shape and corresponding to the through-hole conductor22is formed coaxially with and substantially in the same shape as the pad portion23of the coil pattern12at the other end portion of the conductor pattern27. As illustrated inFIG.2, the one end portion of the conductor pattern27is connected to the other end portion of the lead conductor14via the through-hole conductor25, and the other end portion of the conductor pattern27is connected to an end portion of the coil pattern12via the through-hole conductor22.

As illustrated inFIG.3, the multilayer coil component1is mounted on a mounting substrate100. The mounting substrate100includes a substrate101, conductor layers102and103, and resists104and105. The substrate101is a flat plate member that serves as a base member of the mounting substrate100. The conductor layers102and103are formed on the surface of the substrate101with a conductive material. The conductor layer102and the conductor layer103are disposed apart from each other in the Y-axis direction. The resists104and105are insulating layers that cover the surfaces of the conductor layers102and103. The resists104and105expose the conductor layers102and103. The multilayer coil component1is mounted on the mounting substrate100with one side surface2dof the pair of side surfaces2cand2das a mounting surface MF. The external electrode4is electrically connected to the conductor layer102, and the external electrode5is electrically connected to the conductor layer103. The external electrode4and the conductor layer102are fixed by solder106. The external electrode5and the conductor layer103are fixed by solder107. The multilayer coil component1is mounted on the mounting substrate100in a state where the coil axis L extends along the surface of the substrate101.

Next, a configuration of the conductor pattern21forming the coil pattern12will be described in detail with reference toFIG.4A. As illustrated inFIG.4A, a cross section of the element body2and the coil10have a rectangular shape with the Z-axis direction as the longitudinal direction and the X-axis direction as the lateral direction. The coil10includes a pair of coil conductors31and32extending in the X-axis direction, which is the lateral direction, and a pair of coil conductors33and34extending in the Z-axis direction, which is the longitudinal direction. Note that cross-sectional shapes of the element body2and the coil10are not particularly limited, and may be a rectangular shape in which the X-axis direction is the longitudinal direction and the Z-axis direction is the lateral direction, or may be a square shape.

The coil conductors31and32are apart from each other in the Z-axis direction, the coil conductor31is disposed on the positive side in the Z-axis direction, and the coil conductor32is disposed on the negative side in the Z-axis direction. The coil conductor31is disposed at a position apart from the side surface2ctoward the negative side in the Z-axis direction. The coil conductor32is disposed at a position apart from the side surface2dtoward the positive side in the Z-axis direction. The coil conductors33and34are apart from each other in the X-axis direction, the coil conductor33is disposed on the positive side in the X-axis direction, and the coil conductor34is disposed on the negative side in the X-axis direction. The coil conductor33is disposed at a position apart from the side surface2etoward the negative side in the X-axis direction. The coil conductor34is disposed at a position apart from the side surface2ftoward the positive side in the X-axis direction.

End portions of the coil conductor33on the positive side and the negative side in the Z-axis direction are connected to end portions of the coil conductors31and32on the positive side in the X-axis direction. End portions of the coil conductor34on the positive side and the negative side in the Z-axis direction are connected to end portions of the coil conductors31and32on the negative side in the X-axis direction. As a result, the coil conductors31,32,33, and34form a rectangular annular shape as viewed in the Y-axis direction. Note that the coil pattern12illustrated inFIG.4Aincludes the coil conductors32,33, and34, and is opened on the positive side in the Z-axis direction. Regarding the dimensional relationship described below, the same relationship holds for other than the coil pattern12illustrated inFIG.4A.

Next, a dimensional relationship of the multilayer coil component1will be described. The size of a gap in the Z-axis direction between the coil10and the mounting surface MF in a cross section viewed in the Y-axis direction is defined as a first gap G1. The size of a gap in the X-axis direction between the coil10and the side surfaces2eand2fin the cross section viewed in the Y-axis direction is defined as a second gap G2. The size of the first gap G1is a dimension in the Z-axis direction between an edge portion of the coil conductor32on the negative side in the Z-axis direction and the side surface2d. The size of the second gap G2is a dimension in the X-axis direction between an edge portion of the coil conductor33on the positive side in the X-axis direction and the side surface2e. Alternatively, the size of the second gap G2is a dimension in the X-axis direction between an edge portion of the coil conductor34on the negative side in the X-axis direction and the side surface2f. Note that the second gap G2on the coil conductor33side and the second gap G2on the coil conductor34side are not necessarily the same, and may be different from each other. In this case, an average value of the second gap on the coil conductor33side and the second gap on the coil conductor34side is adopted as the second gap G2. Note that when a dimension in the Z-axis direction between an edge portion of the coil conductor31on the positive side in the Z-axis direction and the side surface2cis defined as a third gap G3, the third gap G3may have the same dimension as the first gap G1. However, the third gap G3may have a dimension different from that of the first gap G1. The third gap G3may have the same dimensional condition as the first gap G1described below. However, a dimensional relationship of the third gap G3is not particularly limited, and may not have the dimensional condition of the first gap G1.

In the cross section viewed in the Y-axis direction, the first gap G1in the Z-axis direction between the coil10and the mounting surface MF is larger than the second gap G2in the X-axis direction between the coil10and the side surfaces2eand2f. Specifically, the first gap G1may be 1.2 times or more, and may be 1.8 times or more the second gap G2. As a result, a distance for suppressing a crack can be secured between the mounting surface MF, which is distorted by stress, and the coil10in the element body2. The first gap G1may be 6.0 times or less, and may be 3.0 times or less the second gap G2. As a result, it is possible to suppress a deterioration in inductance characteristics due to a decrease in the inner diameter of the coil. When the upper limit is exceeded, the inner diameter of the coil may be reduced, leading to a deterioration in inductance characteristics.

In the cross section viewed in the Y-axis direction, the ratio of the first gap G1to the dimension L1, which is the size of the element body2in the Z-axis direction, may be 12% or more, and may be 18% or more. As a result, a distance for suppressing a crack can be secured between the mounting surface MF, which is distorted by stress, and the coil10in the element body2. In addition, in the cross section viewed in the Y-axis direction, the ratio of the first gap G1to the dimension L1, which is the size of the element body2in the Z-axis direction, may be 30% or less, and may be 25% or less. As a result, it is possible to suppress a deterioration in inductance characteristics due to a decrease in the inner diameter of the coil. When the upper limit is exceeded, the inner diameter of the coil may be reduced, leading to a deterioration in inductance characteristics.

FIG.5is an enlarged cross-sectional view of the vicinity of the mounting surface MF as viewed in the Y-axis direction. As illustrated inFIG.5, in a first region E1between the mounting surface MF and the coil10in the element body2, a surface layer region EA constituting the mounting surface MF and an internal region EB on the inner side of the surface layer region EA are formed. The surface layer region EA is a region having a predetermined thickness from the side surface2dtoward the positive side in the Z-axis direction. The internal region EB is a region on the positive side of the surface layer region EA in the Z-axis direction. The surface layer region EA and the internal region EB may be formed substantially in the entire region of the element body2in the Y-axis direction. The surface layer region EA is a region having a larger average crystal grain size than the internal region EB. Such a surface layer region EA is formed by making the sinterability of the surface layer region EA higher than that of the internal region EB. The ratio of the average crystal grain size of the surface layer region EA to the average crystal grain size of the internal region EB may be in a range of 1.2 to 2.0. Note that the average crystal grain size of the surface layer region EA is not particularly limited, but may be set to 0.5 to 3.0 μm. The thickness of the surface layer region EA is not particularly limited, but may be set to 2 to 8 μm.

The surface layer region EA may be 2% or more, and may be 3% or more of the first region E1. In this case, the surface layer region EA can secure a thickness for suppressing the occurrence of a crack. The surface layer region EA may be 25% or less, and may be 20% or less of the first region E1. Note that the ratio of the surface layer region EA to the first region E1may be an average value of the ratio of the thickness of the surface layer region EA to the thickness of the first region E1in the Z-axis direction at each position in the X-axis direction. In this case, it is possible to secure the thickness of the internal region EB sufficient for suppressing the progress of a crack. Note that a second region E2between the side surface2cand the coil10in the element body2, a third region E3between the side surface2eand the coil10in the element body2, and a fourth region E4between the side surface2fand the coil10in the element body2may have the same layer structure as the first region E1.

Next, functions and effects of the multilayer coil component1according to the present embodiment will be described.

The multilayer coil component1includes the coil10disposed inside the element body2and having the coil axis L extending in the Y-axis direction orthogonal to the Z-axis direction and the X-axis direction. In addition, the side surface2d, which is one of the pair of side surfaces2cand2dopposite to each other in the Z-axis direction, is the mounting surface MF. Therefore, the multilayer coil component1is mounted in such an arrangement that the coil axis L extends along the surface of the mounting substrate100(seeFIG.3). At this time, stress is applied to the mounting surface MF of the multilayer coil component1due to the influence of expansion, contraction, and the like of the conductor layers102and103of the mounting substrate100.

Here, a multilayer coil component200according to a comparative example will be described with reference toFIGS.4B,6A,6B, and6C. As illustrated inFIG.4B, in the multilayer coil component200, the first gap G1is equal to the second gap G2. In addition, the ratio of the first gap G1to the dimension L1of the element body2is less than 12%. Next, with reference toFIGS.6A to6C, a principle in which a crack may occur at the time of mounting the multilayer coil component will be described. First, as illustrated inFIG.6A, cream solder108is applied onto the conductor layers102and103of the mounting substrate100. Then, the multilayer coil component200is mounted on the conductor layers102and103via the cream solder108. Next, as illustrated inFIG.6B, when solder reflow mounting is performed, the conductor layers102and103of the mounting substrate100expand in a reflow furnace at a high temperature. The conductor layers102and103expand so as to approach the central position of the element body2. Next, as illustrated inFIG.6C, when the reflow is completed and the temperature decreases, the conductor layers102and103contract so as to move away from the central position of the element body2. The contraction stress of the conductor layers102and103applies stress so as to horizontally extend the mounting surface MF of the multilayer coil component1mounted via the solders106and107. At this time, when the strength of the element body2is insufficient, a crack CR1occurs in the vertical direction. In addition, a crack CR2reaching the coil10is formed in the vicinity of a corner portion of the element body2from an end portion of a wraparound portion of the external electrodes4and5toward the mounting surface MF side. Note that a mounting procedure as illustrated inFIGS.6A to6Cis also applied to the multilayer coil component1according to the present embodiment.

On the other hand, in the cross section viewed in the Y-axis direction, the ratio of the first gap G1in the Z-axis direction between the coil10and the mounting surface MF to the size of the element body2in the Z-axis direction is 12 to 30%. In this case, a distance for suppressing a crack can be secured between the mounting surface MF, which is easily distorted by stress, and the coil10in the element body2. As described above, a crack due to stress at the time of mounting can be suppressed.

In the cross section viewed in the Y-axis direction, the first gap G1may be larger than the second gap G2in the X-axis direction between the coil10and the side surfaces2eand2f. In this case, a distance for suppressing a crack can be secured between the mounting surface MF, which is easily distorted by stress, and the coil10in the element body2.

The first gap G1may be 1.2 to 6.0 times the second gap G2. In this case, a distance for suppressing a crack can be secured between the mounting surface MF, which is easily distorted by stress, and the coil10in the element body2.

Here, the effect of suppressing a crack by increasing the first gap G1will be described in more detail. As illustrated inFIG.3, in an insulator material portion on the outer peripheral side of the coil10, a region DE1(illustrated in gray inFIG.3) having the mounting surface MF is a region that is easily distorted by stress due to expansion and contraction of the conductor layers102and103. Since a distance of the region DE1in the Z-axis direction is large, the stress acting per unit volume in the region DE1is reduced. As a result, the occurrence of the cracks CR1and CR2(seeFIG.6C) is suppressed. In addition, even if the crack CR2occurs at the corner portion, the coil pattern12of the coil10is largely separated from the mounting surface MF, so that it is possible to prevent the crack CR2from reaching the coil pattern12and disconnecting the coil pattern12. In addition, it is possible to prevent the crack CR2from blocking a magnetic flux B generated in the coil10.

FIG.8illustrates a result of an experiment for confirming the effect of increasing the first gap G1. In this experiment, the dimension L1=275 μm, the dimension L2=185 μm, the dimension L3=360 μm, and the gap G2=15 μm. On the other hand, six types of multilayer coil components having different first gaps G1were prepared. One hundred pieces were prepared for each type and mounted on mounting substrates. When the crack CR1extending in the vertical direction (seeFIG.6C) could be observed in appearance, it was regarded as “crack occurrence”, and the ratio was calculated. A graph of the calculation result is illustrated inFIG.8. InFIG.8, the vertical axis represents the crack occurrence rate, which is the ratio of the number of cracks that occurred in the 100 pieces. The horizontal axis represents the ratio of the gap G1to the dimension L1. As illustrated inFIG.8, by setting the ratio of the gap G1to the dimension L1to 12% or more, it was possible to confirm the effect of suppressing the crack occurrence. A plot of the ratio “G1/L1=9%”, that is, the leftmost plot in the graph is the conventional structure according to the comparative example. It was possible to confirm that when the ratio was set to 12% or more, the crack occurrence rate (crack occurrence risk) could be suppressed to about half as compared with the comparative example.

In the first region E1between the mounting surface MF and the coil10in the element body2, the surface layer region EA constituting the mounting surface MF and the internal region EB on the inner side of the surface layer region EA are formed, and the surface layer region EA may have a larger average crystal grain size than the internal region EB. In this case, the occurrence of a crack on the mounting surface MF can be suppressed in the surface layer region EA having a large average crystal grain size. On the other hand, even when a crack occurs on the mounting surface MF, the internal region EB having a small average crystal grain size and having pores can suppress the progress of the crack to the inside.

The surface layer region EA may be 2 to 25% of the first region E1. In this case, the effect of suppressing the occurrence of a crack on the mounting surface MF in the surface layer region EA and the effect of suppressing the progress of the crack in the internal region EB can be obtained in a well-balanced manner.FIGS.7A and7Billustrate enlarged photographs of the vicinity of the surface layer region EA. As illustrated inFIG.7B, in the surface layer region EA serving as a starting point of the crack CR, the strength is high because there are few pores BA, and the crack CR is less likely to occur. Even if the crack CR occurs, there are many pores BA in the internal region EB, so that the crack CR does not proceed straight toward the inside but extends in a random direction so as to run between the pores BA. Therefore, the progress of the crack CR is suppressed in the internal region EB.

For example, configurations illustrated inFIGS.9A and9Bmay be adopted. As illustrated inFIGS.9A and9B, the element body2may have buffer portions50having a high cushioning property on both sides in the Y-axis direction. The buffer portion50is provided at each of places having the end surfaces2aand2bin the element body2. The buffer portion50has a structure having a low Young's modulus. A standard portion sandwiched between the pair of buffer portions50is a portion whose Young's modulus is set to a standard value of the element body2, and has a Young's modulus higher than that of the buffer portion50. The size of the buffer portion50is not particularly limited, and the buffer portion50may extend to the coil10as illustrated inFIG.9A, or the buffer portion50may be formed in a range not extending to the coil10as illustrated inFIG.9B.

REFERENCE SIGNS LIST