Inductor Components

Abstract

To provide an inductor component that can prevent disconnection between a via wiring layer and a coil wiring layer.SOLUTION: An inductor component 1 includes an element assembly 10, a coil 20 provided in the element assembly and wound in a spiral shape along an axis, and a first external electrode 30 and a second external electrode 40 provided in the element assembly and electrically connected to the coil. The coil 20 includes a plurality of coil wiring layers stacked along the axis, and a plurality of via wiring layers 61 to 66 connecting the coil wiring layers adjacent to each other in the axis direction. When seen from an axis AX direction, the via wiring layers include bottom surface side via wiring layers 61, 62, 65, and 66 extending along a spiral direction of the coil 20 and existing on a bottom surface side with respect to a central line N between a top surface 18 and a bottom surface 17 of the element assembly 10, and top surface side via wiring layers 63 and 64 existing on a top surface side with respect to the central line N. A contact area between the bottom surface side via wiring layer and the coil wiring layer is large than a contact area between the top surface side via wiring layer and the coil wiring layer.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to inductor components. [Background technology]

[0002] A conventional inductor component is described in Japanese Patent Laid-Open No. 2000-286125 (Patent Document 1). This inductor component has an element body, a coil provided within the element body and wound spirally along an axis, and first and second external electrodes provided on the element body and electrically connected to the coil. The coil has multiple coil wiring layers stacked along the axis and multiple via wiring layers connecting adjacent coil wiring layers in the axial direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-286125 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, efforts have been made to miniaturize inductor components. In this situation, when mounting the conventional inductor components described above on a mounting board, it has been found that large stress is applied to the connection between the via wiring layer and the coil wiring layer due to thermal stress and bending stress from the mounting board, which may cause the connection between the via wiring layer and the coil wiring layer to peel off.

[0005] Therefore, an object of the present disclosure is to provide an inductor component that can prevent separation of the connection between a via wiring layer and a coil wiring layer. [Means for solving the problem]

[0006] In order to solve the above problems, an inductor component according to one aspect of the present disclosure comprises: The base body and a coil provided within the element body and wound spirally along an axis; a first external electrode and a second external electrode provided on the element body and electrically connected to the coil; Equipped with the element body includes a first end face and a second end face facing each other, a first side face and a second side face facing each other, a bottom face connected between the first end face and the second end face and between the first side face and the second side face, and a top face facing the bottom face, the first external electrode and the second external electrode are provided at least on the bottom surface, the axis is parallel to the bottom surface and intersects the first side surface and the second side surface; the coil has a plurality of coil wiring layers stacked along the axis and a plurality of via wiring layers connecting adjacent coil wiring layers in the axial direction, When viewed from the axial direction, the plurality of via wiring layers extend along a spiral direction of the coil, and the plurality of via wiring layers include a bottom surface-side via wiring layer located on the bottom surface side with respect to a center line between the top surface and the bottom surface of the element body, and a top surface-side via wiring layer located on the top surface side with respect to the center line, The contact area between the bottom surface side via wiring layer and the coil wiring layer is larger than the contact area between the top surface side via wiring layer and the coil wiring layer.

[0007] Here, a bottom-side via wiring layer located on the bottom side of the center line of the element body refers to a via wiring layer among the multiple via wiring layers, the center point of which along the extension direction of the via wiring layer as viewed from the axial direction is located on the bottom side of the center line of the element body that passes through the center of gravity of the element body and is parallel to the bottom and top surfaces.Similarly, a top-side via wiring layer located on the top side of the center line of the element body refers to a via wiring layer among the multiple via wiring layers, the center point of which along the extension direction of the via wiring layer as viewed from the axial direction is located on the top side of the center line of the element body that passes through the center of gravity of the element body and is parallel to the bottom and top surfaces.

[0008] The contact area between the bottom-side via wiring layer and the coil wiring layer is the average of all the contact areas measured between each bottom-side via wiring layer and the coil wiring layer when there are multiple bottom-side via wiring layers.Similarly, the contact area between the top-side via wiring layer and the coil wiring layer is the average of all the contact areas measured between each top-side via wiring layer and the coil wiring layer when there are multiple top-side via wiring layers.

[0009] According to the above aspect, the contact area between the bottom-side via wiring layer and the coil wiring layer is larger than the contact area between the top-side via wiring layer and the coil wiring layer. Therefore, when mounting an inductor component on a mounting board so that the bottom side of the element body faces the mounting board, the connection strength between the bottom-side via wiring layer closer to the mounting board and the coil wiring layer can be further improved.

[0010] This prevents the bottom-side via wiring layer from peeling off from the coil wiring layer even when a large stress is applied to the connection between the bottom-side via wiring layer and the coil wiring layer due to thermal stress or bending stress from the mounting substrate during mounting, and therefore prevents the bottom-side via wiring layer from peeling off from the coil wiring layer even in the current trend toward miniaturization of inductor components. [Effects of the Invention]

[0011] According to the inductor component of one aspect of the present disclosure, it is possible to prevent separation of the connection between the via wiring layer and the coil wiring layer. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a perspective view showing a first embodiment of an inductor component. [Figure 2] 3 is a perspective front view of the inductor component as seen from a first side surface side. FIG. [Figure 3A] FIG. 2 is an exploded plan view of the inductor component. [Figure 3B] FIG. 2 is an exploded plan view of the inductor component. [Figure 3C] FIG. 2 is an exploded plan view of the inductor component. [Figure 4]10 is a perspective front view of an inductor component according to a second embodiment of the present invention, seen from a first side surface side of the inductor component. FIG. [Figure 5A] FIG. 2 is an exploded plan view of the inductor component. [Figure 5B] FIG. 2 is an exploded plan view of the inductor component. [Figure 5C] FIG. 2 is an exploded plan view of the inductor component. [Figure 6] 10 is a perspective front view of an inductor component according to a third embodiment, seen from a first side surface side of the inductor component. FIG. [Figure 7A] FIG. 2 is an exploded plan view of the inductor component. [Figure 7B] FIG. 2 is an exploded plan view of the inductor component. [Figure 7C] FIG. 2 is an exploded plan view of the inductor component. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, an inductor component according to one aspect of the present disclosure will be described in detail with reference to the illustrated embodiments. Note that the drawings include some schematic views and may not reflect actual dimensions or proportions.

[0014] (First embodiment) FIG. 1 is a perspective view showing a first embodiment of an inductor component. FIG. 2 is a see-through front view of the inductor component as seen from a first side surface. FIGS. 3A, 3B, and 3C are exploded plan views of the inductor component. As shown in FIGS. 1, 2, 3A, 3B, and 3C, the inductor component 1 includes an element body 10, a coil 20 provided within the element body 10 and wound spirally along an axis AX, and a first external electrode 30 and a second external electrode 40 provided in the element body 10 and electrically connected to the coil 20. For convenience, the element body and coil are depicted as transparent in FIG. 2 to facilitate understanding of the structure, but they may also be translucent or opaque.

[0015] The inductor component 1 is electrically connected to wiring on a circuit board (not shown) via first and second external electrodes 30, 40. The inductor component 1 is used, for example, as an impedance matching coil (matching coil) for high-frequency circuits, and is used in electronic devices such as personal computers, DVD players, digital cameras, TVs, mobile phones, car electronics, and medical and industrial machinery. However, the uses of the inductor component 1 are not limited to this, and it can also be used, for example, in tuning circuits, filter circuits, rectifying and smoothing circuits, and the like.

[0016] The element body 10 is formed in a substantially rectangular parallelepiped shape. The surfaces of the element body 10 include a first end face 15 and a second end face 16 that face each other, a first side face 13 and a second side face 14 that face each other, a bottom face 17 that is connected between the first end face 15 and the second end face 16 and between the first side face 13 and the second side face 14, and a top face 18 that faces the bottom face 17. The bottom face 17 is the face that faces the mounting board (not shown) when the inductor component 1 is mounted on the mounting board.

[0017] As shown in the figure, the X direction is perpendicular to the first end face 15 and the second end face 16 and is the direction from the first end face 15 to the second end face 16. The Y direction is perpendicular to the first side face 13 and the second side face 14 and is the direction from the second side face 14 to the first side face 13. The Z direction is perpendicular to the bottom face 17 and the top face 18 and is the direction from the bottom face 17 to the top face 18. The X direction is also referred to as the length direction of the element body 10, the Y direction is also referred to as the width direction of the element body 10, and the Z direction is also referred to as the height direction of the element body 10. The X direction, Y direction, and Z direction are perpendicular to each other and, when arranged in the order X, Y, Z, form a left-handed system.

[0018] The element body 10 is formed by stacking multiple insulating layers 11. The insulating layers 11 are made of, for example, a material primarily composed of borosilicate glass, ferrite, resin, or other material. The stacking direction of the insulating layers 11 is a direction (Y direction) parallel to the first and second end faces 15 and 16 and the bottom face 17 of the element body 10. That is, the insulating layers 11 are layered and extend across the XZ plane. In this application, "parallel" is not limited to a strict parallel relationship, but also includes a substantial parallel relationship, taking into account a realistic range of variation. Note that in the element body 10, the interfaces between the multiple insulating layers 11 may not be clear due to firing or other reasons. Note that in Figures 3A, 3B, and 3C, the stacking direction (Y direction) is from top to bottom.

[0019] The first external electrode 30 and the second external electrode 40 are made of a conductive material such as Ag, Cu, Au, or an alloy containing any of these as its main components. The first external electrode 30 is L-shaped and extends from the first end face 15 to the bottom face 17. The first external electrode 30 is embedded in the element body 10 so as to be exposed from the first end face 15 and the bottom face 17. The first external electrode 30 has a first end face portion 31 that extends along the first end face 15, and a first bottom face portion 32 that is connected to the first end face portion 31 and extends along the bottom face 17.

[0020] The second external electrode 40 has an L-shape extending from the second end face 16 to the bottom face 17. The second external electrode 40 is embedded in the element body 10 so as to be exposed from the second end face 16 and the bottom face 17. The second external electrode 40 has a second end face portion 41 extending along the second end face 16, and a second bottom face portion 42 connected to the second end face portion 41 and extending along the bottom face 17.

[0021] The first external electrode 30 has a configuration in which a plurality of first external electrode conductor layers 33 embedded in the element body 10 (insulating layer 11) are laminated. The second external electrode 40 has a configuration in which a plurality of second external electrode conductor layers 43 embedded in the element body 10 (insulating layer 11) are laminated. The first external electrode conductor layers 33 extend along the first end face 15 and the bottom face 17, and the second external electrode conductor layers 43 extend along the second end face 16 and the bottom face 17.

[0022] This allows the first and second external electrodes 30, 40 to be embedded within the element body 10, thereby making it possible to reduce the size of the inductor component compared to a configuration in which external electrodes are externally attached to the element body 10. Furthermore, the coil 20 and the external electrodes 30, 40 can be formed in the same process, reducing variation in the positional relationship between the coil 20 and the external electrodes 30, 40, thereby reducing variation in the electrical characteristics of the inductor component 1.

[0023] The first external electrode 30 may be composed of a first bottom surface portion 32 without having a first end surface portion 31, and similarly, the second external electrode 40 may be composed of a second bottom surface portion 42 without having a second end surface portion 41. In other words, it is sufficient that the first external electrode 30 and the second external electrode 40 are provided at least on the bottom surface 17 of the element body 10.

[0024] The coil 20 is made of, for example, the same conductive material as the first and second external electrodes 30, 40. The coil 20 is wound spirally along the lamination direction of the insulating layers 11. A first end of the coil 20 is connected to the first external electrode 30, and a second end of the coil 20 is connected to the second external electrode 40. In this embodiment, the coil 20 and the first and second external electrodes 30, 40 are integrated and no clear boundary exists between them, but this is not limiting, and a boundary may exist between them by forming the coil and the external electrodes using different materials or different manufacturing methods.

[0025] The coil 20 is wound along the axis AX so that the axis AX is parallel to the bottom surface 17 and intersects the first side surface 13 and the second side surface 14. The axis AX of the coil 20 coincides with the lamination direction (Y direction) of the insulating layers 11. The axis AX of the coil 20 refers to the central axis of the spiral shape of the coil 20.

[0026] The coil 20 has a winding portion 20a, a first lead portion 20b connected between a first end of the winding portion 20a and the first external electrode 30, and a second lead portion 20c connected between a second end of the winding portion 20a and the second external electrode 40. In this embodiment, the winding portion 20a and the first and second lead portions 20b, 20c are integrated together, and no clear boundary exists between them, but this is not limiting, and a boundary may exist between the winding portion and the lead portions by forming them using different materials or different manufacturing methods.

[0027] The winding portion 20a is wound spirally along the axis AX. That is, the winding portion 20a refers to the spirally wound portion where the coils 20 overlap each other when viewed parallel to the axis AX. The first and second lead-out portions 20b and 20c refer to the portions outside the overlapping portions.

[0028] When viewed in the direction of the axis AX of the coil 20, the shape of the coil 20 is symmetrical with respect to a line that passes through the axis AX of the coil 20 and is parallel to the Z direction. This makes it possible to suppress variations in the characteristics of the inductor component 1.

[0029] 3A, 3B, and 3C, the coil 20 has a plurality of coil wiring layers 51-57 stacked along the axis AX, and a plurality of via wiring layers 61-66 located between adjacent coil wiring layers in the direction of the axis AX and connecting the adjacent coil wiring layers in the direction of the axis AX. The plurality of coil wiring layers 51-57 are each provided on an insulating layer 11, and the plurality of via wiring layers 61-66 are each provided on an insulating layer 11. When viewed in the direction of the axis AX, the plurality of coil wiring layers 51-57 and the plurality of via wiring layers 61-66 extend along the spiral direction of the coil 20.

[0030] The multiple coil wiring layers 51-57 are each wound along a plane and electrically connected in series to form a spiral. The multiple coil wiring layers 51-57 are wound on the main surface (XZ plane) of the insulating layer 11 that is perpendicular to the axial direction AX (Y direction). The number of turns of each coil wiring layer 51-57 is less than one turn, but may be one or more turns.

[0031] The via wiring layers 61 to 66 penetrate the insulating layer 11 in the thickness direction (Y direction). The coil wiring layers adjacent to each other in the stacking direction are electrically connected in series through the via wiring layers. In this way, the coil wiring layers 51 to 57 are electrically connected in series to each other and form a spiral.

[0032] Specifically, the first coil wiring layer 51, the second coil wiring layer 52, the third coil wiring layer 53, the fourth coil wiring layer 54, the fifth coil wiring layer 55, the sixth coil wiring layer 56, and the seventh coil wiring layer 57 are stacked in this order along the Y direction. An end of the first coil wiring layer 51 is connected to the first external electrode conductor layer 33 of the first external electrode 30. An end of the seventh coil wiring layer 57 is connected to the second external electrode conductor layer 43 of the second external electrode 40.

[0033] The first via wiring layer 61 is located between the first coil wiring layer 51 and the second coil wiring layer 52, and connects an end of the first coil wiring layer 51 to an end of the second coil wiring layer 52. The second via wiring layer 62 is located between the second coil wiring layer 52 and the third coil wiring layer 53, and connects an end of the second coil wiring layer 52 to an end of the third coil wiring layer 53. The third via wiring layer 63 is located between the third coil wiring layer 53 and the fourth coil wiring layer 54, and connects an end of the third coil wiring layer 53 to an end of the fourth coil wiring layer 54.

[0034] The fourth via wiring layer 64 is located between the fourth coil wiring layer 54 and the fifth coil wiring layer 55, and connects an end of the fourth coil wiring layer 54 to an end of the fifth coil wiring layer 55. The fifth via wiring layer 65 is located between the fifth coil wiring layer 55 and the sixth coil wiring layer 56, and connects an end of the fifth coil wiring layer 55 to an end of the sixth coil wiring layer 56. The sixth via wiring layer 66 is located between the sixth coil wiring layer 56 and the seventh coil wiring layer 57, and connects an end of the sixth coil wiring layer 56 to an end of the seventh coil wiring layer 57.

[0035] 2, 3A, 3B, and 3C, when viewed in the direction of axis AX, the multiple via wiring layers 61-66 include a bottom-side via wiring layer located on the bottom surface 17 side of a center line N between the top surface 18 and bottom surface 17 of the element body 10, and a top-side via wiring layer located on the top surface 18 side of the center line N. The center line N is a straight line that passes through the center of gravity of the element body 10 and is parallel to the top surface 18 and the bottom surface 17. In FIG. 2, the center line N passes through the axis AX and overlaps with the center of gravity of the element body 10, but the center line N or the center of gravity of the element body 10 may be spaced apart from the axis AX. Note that the center of gravity here refers to the center point of the length, height, and width dimensions of the element body 10, and the weight of the component is not taken into consideration.

[0036] The bottom surface side via wiring layer is a via wiring layer among the multiple via wiring layers 61 to 66, the center point of the extension direction of the via wiring layer as viewed from the axis AX direction being located closer to the bottom surface 17 than the center line N of the element body 10. Specifically, the bottom surface side via wiring layers are the first via wiring layer 61, the second via wiring layer 62, the fifth via wiring layer 65, and the sixth via wiring layer 66.

[0037] A center point 61a of the center line (shown by a dashed line) along the extension direction of the first via wiring layer 61 is located closer to the bottom surface 17 than the center line N. A center point 62a of the center line (shown by a dashed line) along the extension direction of the second via wiring layer 62 is located closer to the bottom surface 17 than the center line N. A center point 65a of the center line (shown by a dashed line) along the extension direction of the fifth via wiring layer 65 is located closer to the bottom surface 17 than the center line N. A center point 66a of the center line (shown by a dashed line) along the extension direction of the sixth via wiring layer 66 is located closer to the bottom surface 17 than the center line N.

[0038] The top surface side via wiring layer is a via wiring layer among the multiple via wiring layers 61 to 66, the center point of the extension direction of the via wiring layer being located closer to the top surface 18 than the center line N of the element body 10 when viewed from the axis AX direction. Specifically, the top surface side via wiring layers are the third via wiring layer 63 and the fourth via wiring layer 64.

[0039] The center point 63a of the center line (shown by the dashed line) along the extension direction of the third via wiring layer 63 is located closer to the top surface 18 than the center line N. The center point 64a of the center line (shown by the dashed line) along the extension direction of the fourth via wiring layer 64 is located closer to the top surface 18 than the center line N.

[0040] The contact area between the bottom-side via wiring layer and the coil wiring layer is larger than the contact area between the top-side via wiring layer and the coil wiring layer. Because there are multiple bottom-side via wiring layers, i.e., the first via wiring layer 61, the second via wiring layer 62, the fifth via wiring layer 65, and the sixth via wiring layer 66, the contact area between the bottom-side via wiring layer and the coil wiring layer is calculated by measuring the contact area between each bottom-side via wiring layer and the coil wiring layer and averaging all of these contact areas. Similarly, because there are multiple top-side via wiring layers, i.e., the third via wiring layer 63 and the fourth via wiring layer 64, the contact area between the top-side via wiring layer and the coil wiring layer is calculated by measuring the contact area between each top-side via wiring layer and the coil wiring layer and averaging all of these contact areas.

[0041] Specifically, the first coil wiring layer 51 has a first contact surface S1 in contact with the first via wiring layer 61. The second coil wiring layer 52 has a second contact surface S2 in contact with the first via wiring layer 61 and a third contact surface S3 in contact with the second via wiring layer 62. The third coil wiring layer 53 has a fourth contact surface S4 in contact with the second via wiring layer 62 and a fifth contact surface S5 in contact with the third via wiring layer 63. The fourth coil wiring layer 54 has a sixth contact surface S6 in contact with the third via wiring layer 63 and a seventh contact surface S7 in contact with the fourth via wiring layer 64. The fifth coil wiring layer 55 has an eighth contact surface S8 in contact with the fourth via wiring layer 64 and a ninth contact surface S9 in contact with the fifth via wiring layer 65. The sixth coil wiring layer 56 has a tenth contact surface S10 in contact with the fifth via wiring layer 65 and an eleventh contact surface S11 in contact with the sixth via wiring layer 66. The seventh coil wiring layer 57 has a twelfth contact surface S12 in contact with the sixth via wiring layer 66.

[0042] The contact surfaces between the bottom-side via wiring layer and the coil wiring layer are the first contact surface S1, the second contact surface S2, the third contact surface S3, the fourth contact surface S4, the ninth contact surface S9, the tenth contact surface S10, the eleventh contact surface S11, and the twelfth contact surface S12. Therefore, the contact area between the bottom-side via wiring layer and the coil wiring layer is the average value of the area of the first contact surface S1, the area of the second contact surface S2, the area of the third contact surface S3, the area of the fourth contact surface S4, the area of the ninth contact surface S9, the area of the tenth contact surface S10, the area of the eleventh contact surface S11, and the area of the twelfth contact surface S12.

[0043] The contact surfaces between the top surface-side via wiring layer and the coil wiring layer are the fifth contact surface S5, the sixth contact surface S6, the seventh contact surface S7, and the eighth contact surface S8. Therefore, the contact surface between the top surface-side via wiring layer and the coil wiring layer is the average area of the fifth contact surface S5, the sixth contact surface S6, the seventh contact surface S7, and the eighth contact surface S8.

[0044] The area of each contact surface can be measured, for example, by polishing the inductor component 1 along the XZ plane. If the entire surface of the via wiring layer is in contact with the coil wiring layer, the cross-sectional area of any cross section of the via wiring layer along the XZ plane may be used as the contact area.

[0045] According to the above configuration, the contact area between the bottom-side via wiring layer and the coil wiring layer is larger than the contact area between the top-side via wiring layer and the coil wiring layer. Therefore, when the inductor component 1 is mounted on a mounting board so that the bottom surface 17 side of the base body 10 faces the mounting board, the connection strength between the bottom-side via wiring layer closer to the mounting board and the coil wiring layer can be further improved.

[0046] This prevents the bottom-side via wiring layer from peeling off from the coil wiring layer even when a large stress is applied to the connection between the bottom-side via wiring layer and the coil wiring layer due to thermal stress or bending stress from the mounting substrate during mounting, and therefore prevents the bottom-side via wiring layer from peeling off from the coil wiring layer even in the current trend toward miniaturization of inductor components.

[0047] The inventors of the present application have found that the stress acting on the side closer to the mounting substrate, i.e., the bottom side, is greater than the stress acting on the side farther from the mounting substrate, i.e., the top side, resulting in significant separation between the bottom-side via wiring layer and the coil wiring layer. Based on this finding, the inventors have conceived of making the contact area between the bottom-side via wiring layer and the coil wiring layer larger than the contact area between the top-side via wiring layer and the coil wiring layer to prevent separation between the bottom-side via wiring layer and the coil wiring layer.

[0048] Furthermore, since the via wiring layer extends along the spiral direction of the coil 20, it is possible to ensure a sufficient contact area between the via wiring layer and the coil wiring layer, thereby improving connection reliability. Furthermore, since the via wiring layer extends along the spiral direction of the coil, it is possible to eliminate via pad portions at the ends of the coil wiring, thereby preventing a decrease in the Q value due to the provision of via pad portions.

[0049] Preferably, the contact area of each of all bottom-side via wiring layers is larger than the contact area of each of all top-side via wiring layers. Specifically, the areas of the first contact surface S1, the second contact surface S2, the third contact surface S3, the fourth contact surface S4, the ninth contact surface S9, the tenth contact surface S10, the eleventh contact surface S11, and the twelfth contact surface S12 are each larger than the areas of the fifth contact surface S5, the sixth contact surface S6, the seventh contact surface S7, and the eighth contact surface S8, respectively.

[0050] Preferably, the total contact area of each bottom-side via wiring layer is larger than the total contact area of each top-side via wiring layer. Specifically, the total of the areas of the first contact surface S1, the second contact surface S2, the third contact surface S3, the fourth contact surface S4, the ninth contact surface S9, the tenth contact surface S10, the eleventh contact surface S11, and the twelfth contact surface S12 is larger than the total of the areas of the fifth contact surface S5, the sixth contact surface S6, the seventh contact surface S7, and the eighth contact surface S8.

[0051] As shown in Figures 3A, 3B, and 3C, the length of the bottom-side via wiring layer is longer than the length of the top-side via wiring layer when viewed from the direction of axis AX. The length of the bottom-side via wiring layer is the length of the center line along the extension direction of the bottom-side via wiring layer when viewed from the direction of axis AX. Since there are multiple bottom-side via wiring layers, the length of the bottom-side via wiring layer is measured and the average value of all the lengths. Similarly, the length of the top-side via wiring layer is the length of the center line along the extension direction of the top-side via wiring layer when viewed from the direction of axis AX. Since there are multiple top-side via wiring layers, the length of the top-side via wiring layer is measured and the average value of all the lengths.

[0052] Specifically, the length of the bottom surface side via wiring layer is the average value (hereinafter referred to as the first average value) of the first length L1 of the first via wiring layer 61, the second length L2 of the second via wiring layer 62, the fifth length L5 of the fifth via wiring layer 65, and the sixth length L6 of the sixth via wiring layer 66. The length of the top surface side via wiring layer is the average value (hereinafter referred to as the second average value) of the third length L3 of the third via wiring layer 63 and the fourth length L4 of the fourth via wiring layer 64. The first average value is longer than the second average value.

[0053] The length of each via wiring layer is measured, for example, by polishing the inductor component 1 along the XZ plane and measuring the length of each via wiring layer.

[0054] According to the above configuration, the length of the bottom-side via wiring layer is longer than the length of the top-side via wiring layer when viewed from the direction of the axis AX, so that the strength of the bottom-side via wiring layer can be improved, and even if a large stress is applied to the bottom-side via wiring layer, damage such as cracks can be prevented from occurring in the bottom-side via wiring layer.

[0055] Preferably, the length of each of all bottom-side via wiring layers is longer than the length of each of all top-side via wiring layers. Specifically, the first length L1, the second length L2, the fifth length L5, and the sixth length L6 are each longer than the third length L3 and the fourth length L4.

[0056] Preferably, the total length of each of the bottom-side via wiring layers is longer than the total length of each of the top-side via wiring layers. Specifically, the total of each of the first length L1, the second length L2, the fifth length L5, and the sixth length L6 is longer than the total of each of the third length L3 and the fourth length L4.

[0057] 2, 3A, 3B, and 3C, the spiral distance between the coils 20 in all of the via wiring layers 61 to 66 is equal when viewed from the direction of the axis AX. The spiral distance between the coils 20 in all of the via wiring layers 61 to 66 refers to the length of the coil wiring layer located between the end of one via wiring layer and the end of the other via wiring layer, in the via wiring layers adjacent to each other in the spiral direction of the coils 20 when viewed from the direction of the axis AX. The length of the coil wiring layer refers to the length of the center line along the extension direction of the coil wiring layer.

[0058] Specifically, when viewed from the direction of the axis AX, the first via wiring layer 61 and the fifth via wiring layer 65 overlap, and the second via wiring layer 62 and the sixth via wiring layer 66 overlap. When viewed from the direction of the axis AX, the distance between the first via wiring layer 61 and the second via wiring layer 62 and the distance between the fifth via wiring layer 65 and the sixth via wiring layer 66 are equal, and this distance is defined as a first distance K1. Furthermore, the distance between the second via wiring layer 62 and the third via wiring layer 63 and the distance between the sixth via wiring layer 66 and the third via wiring layer 63 are equal, and this distance is defined as a second distance K2. Furthermore, the distance between the third via wiring layer 63 and the fourth via wiring layer 64 is defined as a third distance K3. Furthermore, the distance between the fourth via wiring layer 64 and the first via wiring layer 61 and the distance between the fourth via wiring layer 64 and the fifth via wiring layer 65 are equal, and this distance is defined as a fourth distance K4. The first distance K1, the second distance K2, the third distance K3, and the fourth distance K4 are all equal. Note that, in the first via wiring layer 61 and the fifth via wiring layer 65 that overlap each other when viewed in the direction of the axis AX, the distance between the first via wiring layer 61 and the fifth via wiring layer 65 is not measured. In addition, in the second via wiring layer 62 and the sixth via wiring layer 66 that overlap each other when viewed in the direction of the axis AX, the distance between the second via wiring layer 62 and the sixth via wiring layer 66 is not measured.

[0059] The method for measuring the distance between the via wiring layers is, for example, to polish the inductor component 1 along the XZ plane and measure the distance between the via wiring layers.

[0060] According to the above configuration, it is possible to disperse current concentration points in the current path of the coil 20, making it difficult for current loss to occur. In other words, when viewed from the direction of the axis AX, the portions between adjacent via wiring layers in the spiral direction of the coil, where current concentration is likely to occur, can be evenly arranged in the spiral direction of the coil 20, thereby dispersing the current concentration points.

[0061] As shown in Figures 2, 3A, 3B, and 3C, the number of bottom-side via wiring layers is different from the number of top-side via wiring layers. Preferably, the number of bottom-side via wiring layers is greater than the number of top-side via wiring layers. Specifically, the bottom-side via wiring layers are the first via wiring layer 61, the second via wiring layer 62, the fifth via wiring layer 65, and the sixth via wiring layer 66, so the number of bottom-side via wiring layers is four. The top-side via wiring layers are the third via wiring layer 63 and the fourth via wiring layer 64, so the number of top-side via wiring layers is two. The above configuration can improve design freedom.

[0062] 2, 3A, 3B, and 3C, the length of the bottom-side via wiring layer is preferably 110% or more and 195% or less of the length of the top-side via wiring layer when viewed in the direction of axis AX. Specifically, the length of the bottom-side via wiring layer is a first average value, and the length of the top-side via wiring layer is a second average value. The first average value is 110% or more and 195% or less of the second average value.

[0063] According to the above configuration, the length of the bottom-side via wiring layer can be increased to improve the strength of the bottom-side via wiring layer. In addition, since the length of the bottom-side via wiring layer is not excessively long, the parallel connection area of the coil wiring layers adjacent to each other in the axial direction AX is not excessively long.

[0064] Preferably, the length of each of all bottom-side via wiring layers is 110% to 195% of the length of each of all top-side via wiring layers. Specifically, the first length L1, the second length L2, the fifth length L5, and the sixth length L6 are 110% to 195% of the third length L3 and the fourth length L4, respectively.

[0065] 2, 3A, 3B, and 3C, preferably, the ratio of the number of bottom-side via wiring layers to the number of top-side via wiring layers is 2:1, and the length of the bottom-side via wiring layer is 110% or more and 125% or less of the length of the top-side via wiring layer as viewed in the direction of axis AX. Specifically, the number of bottom-side via wiring layers is four, and the number of top-side via wiring layers is two. The first average value is 110% or more and 125% or less of the second average value.

[0066] According to the above configuration, the length of the bottom-side via wiring layer can be increased to improve the strength of the bottom-side via wiring layer. In addition, since the length of the bottom-side via wiring layer is not excessively long, the parallel connection area of the coil wiring layers adjacent to each other in the axial direction AX is not excessively long.

[0067] Preferably, the length of each of all bottom-side via wiring layers is 110% to 125% of the length of each of all top-side via wiring layers. Specifically, the first length L1, the second length L2, the fifth length L5, and the sixth length L6 are 110% to 125% of the third length L3 and the fourth length L4, respectively.

[0068] Next, a method for manufacturing the inductor element 1 will be described.

[0069] 3A, 3B, and 3C, the inductor component 1 is manufactured by alternately stacking the first to seventh coil wiring layers 51-57 and the first to sixth via wiring layers 61-66 together with the insulating layer 11 from top to bottom in the figures. The coil wiring layers 51-57 are provided on the insulating layer 11 by, for example, screen printing. Openings are provided in the insulating layer 11 by, for example, photolithography or laser processing, and the via wiring layers 61-66 are provided in the openings by, for example, screen printing.

[0070] (Second embodiment) Fig. 4 is a perspective front view of the inductor component according to a second embodiment, seen from the first side of the inductor component. Figs. 5A, 5B, and 5C are exploded plan views of the inductor component. The second embodiment differs from the first embodiment in the number and length of via wiring layers. This difference in configuration will be described below. The other components are the same as those of the first embodiment, and the same reference numerals as those of the first embodiment will be used, and their description will be omitted.

[0071] 4, 5A, 5B, and 5C, in an inductor component 1A of the second embodiment, a coil 20A has eight coil wiring layers 51 to 58 and seven via wiring layers 61 to 67. Specifically, along the Y direction, a first coil wiring layer 51, a first via wiring layer 61, a second coil wiring layer 52, a second via wiring layer 62, a third coil wiring layer 53, a third via wiring layer 63, a fourth coil wiring layer 54, a fourth via wiring layer 64, a fifth coil wiring layer 55, a fifth via wiring layer 65, a sixth coil wiring layer 56, a sixth via wiring layer 66, a seventh coil wiring layer 57, a seventh via wiring layer 67, and an eighth coil wiring layer 58 are stacked in this order along the Y direction.

[0072] The bottom surface side via wiring layers are a first via wiring layer 61, a second via wiring layer 62, a sixth via wiring layer 66, and a seventh via wiring layer 67. Specifically, a center point 61a of the first via wiring layer 61 is located closer to the bottom surface 17 than the center line N. A center point 62a of the second via wiring layer 62 is located closer to the bottom surface 17 than the center line N. A center point 66a of the sixth via wiring layer 66 is located closer to the bottom surface 17 than the center line N. A center point 67a of the seventh via wiring layer 67 is located closer to the bottom surface 17 than the center line N.

[0073] The top surface side via wiring layers are a third via wiring layer 63, a fourth via wiring layer 64, and a fifth via wiring layer 65. Specifically, a center point 63a of the third via wiring layer 63 is located closer to the top surface 18 than the center line N. A center point 64a of the fourth via wiring layer 64 is located closer to the top surface 18 than the center line N. A center point 65a of the fifth via wiring layer 65 is located closer to the top surface 18 than the center line N.

[0074] As in the first embodiment, the contact area between the bottom-side via wiring layer and the coil wiring layer is larger than the contact area between the top-side via wiring layer and the coil wiring layer. Specifically, the contact area between the bottom-side via wiring layer and the coil wiring layer is the average of the contact surface areas between the first, second, sixth, and seventh via wiring layers 61, 62, 66, and 67 and the first, second, third, sixth, seventh, and eighth coil wiring layers 51, 52, 53, 56, 57, and 58. The contact area between the top-side via wiring layer and the coil wiring layer is the average of the contact surface areas between the third, fourth, and fifth via wiring layers 63, 64, and 65 and the third, fourth, fifth, and sixth coil wiring layers 53, 54, 55, and 56. Therefore, when the inductor component 1A is mounted on a mounting substrate so that the bottom surface 17 of the element body 10 faces the mounting substrate, the connection strength between the bottom-side via wiring layer closer to the mounting substrate and the coil wiring layer can be further improved.

[0075] As in the first embodiment, the length of the bottom-side via wiring layer is longer than the length of the top-side via wiring layer when viewed from the axis AX direction. Specifically, the length of the bottom-side via wiring layer is the average value (hereinafter referred to as the first average value) of the first length L1 of the first via wiring layer 61, the second length L2 of the second via wiring layer 62, the sixth length L6 of the sixth via wiring layer 66, and the seventh length L7 of the seventh via wiring layer 67. The length of the top-side via wiring layer is the average value (hereinafter referred to as the second average value) of the third length L3 of the third via wiring layer 63, the fourth length L4 of the fourth via wiring layer 64, and the fifth length L5 of the fifth via wiring layer 65. The first average value is longer than the second average value. Therefore, the strength of the bottom-side via wiring layer can be improved, and even if a large stress is applied to the bottom-side via wiring layer, damage such as cracks can be prevented from occurring in the bottom-side via wiring layer.

[0076] As in the first embodiment, the spiral distances of the coils 20A in all of the via wiring layers 61 to 67 are equal when viewed along the axis AX. Specifically, when viewed along the axis AX, the first via wiring layer 61 and the sixth via wiring layer 66 overlap, and the second via wiring layer 62 and the seventh via wiring layer 67 overlap. When viewed from the direction of the axis AX, the distance between the first via wiring layer 61 and the second via wiring layer 62, the distance between the sixth via wiring layer 66 and the seventh via wiring layer 67, the distance between the second via wiring layer 62 and the third via wiring layer 63, the distance between the seventh via wiring layer 67 and the third via wiring layer 63, the distance between the third via wiring layer 63 and the fourth via wiring layer 64, the distance between the fourth via wiring layer 64 and the fifth via wiring layer 65, the distance between the fifth via wiring layer 65 and the first via wiring layer 61, and the distance between the fifth via wiring layer 65 and the sixth via wiring layer 66 are all equal. Therefore, current concentration points can be dispersed in the current path of the coil 20A, making it difficult for current loss to occur.

[0077] 4, 5A, 5B, and 5C, the ratio of the number of bottom-side via wiring layers to the number of top-side via wiring layers is 4:3, and the length of the bottom-side via wiring layers is 180% or more and 195% or less of the length of the top-side via wiring layers as viewed in the direction of axis AX. Specifically, the number of bottom-side via wiring layers is four, and the number of top-side via wiring layers is three. The first average value is 180% or more and 195% or less of the second average value.

[0078] According to the above configuration, the length of the bottom-side via wiring layer can be increased to improve the strength of the bottom-side via wiring layer. In addition, since the length of the bottom-side via wiring layer is not excessively long, the area of parallel connection of adjacent coil wiring layers in the AX direction is not excessively long.

[0079] Preferably, the length of each of all bottom-side via wiring layers is 180% to 195% of the length of each of all top-side via wiring layers. Specifically, the first length L1, the second length L2, the sixth length L6, and the seventh length L7 are 180% to 195% of the third length L3, the fourth length L4, and the fifth length L5, respectively.

[0080] (Third embodiment) Fig. 6 is a perspective front view of the inductor component according to a third embodiment, seen from the first side of the inductor component. Figs. 7A, 7B, and 7C are exploded plan views of the inductor component. The third embodiment differs from the first embodiment in the width of the coil wiring layer. This difference in configuration will be described below. The other components are the same as those in the first embodiment, and the same reference numerals as those in the first embodiment will be used, and their description will be omitted.

[0081] 6, 7A, 7B, and 7C, in the coil 20B of the inductor component 1B of the third embodiment, when viewed from the direction of the axis AX, the coil wiring layer in contact with the bottom-side via wiring layer has a bottom-side contact portion in contact with the bottom-side via wiring layer, and the coil wiring layer in contact with the top-side via wiring layer has a top-side contact portion in contact with the top-side via wiring layer.

[0082] Specifically, the bottom surface side via wiring layers are a first via wiring layer 61, a second via wiring layer 62, a fifth via wiring layer 65, and a sixth via wiring layer 66. The top surface side via wiring layers are a third via wiring layer 63 and a fourth via wiring layer 64.

[0083] The first coil wiring layer 51 has a first contact portion 501 in contact with the first via wiring layer 61. The second coil wiring layer 52 has a second contact portion 502 in contact with the first via wiring layer 61 and a third contact portion 503 in contact with the second via wiring layer 62. The third coil wiring layer 53 has a fourth contact portion 504 in contact with the second via wiring layer 62 and a fifth contact portion 505 in contact with the third via wiring layer 63. The fourth coil wiring layer 54 has a sixth contact portion 506 in contact with the third via wiring layer 63 and a seventh contact portion 507 in contact with the fourth via wiring layer 64. The fifth coil wiring layer 55 has an eighth contact portion 508 in contact with the fourth via wiring layer 64 and a ninth contact portion 509 in contact with the fifth via wiring layer 65. The sixth coil wiring layer 56 has a tenth contact portion 510 in contact with the fifth via wiring layer 65 and an eleventh contact portion 511 in contact with the sixth via wiring layer 66. The seventh coil wiring layer 57 has a twelfth contact portion 512 in contact with the sixth via wiring layer 66.

[0084] The bottom surface contact portions are a first contact portion 501, a second contact portion 502, a third contact portion 503, a fourth contact portion 504, a ninth contact portion 509, a tenth contact portion 510, an eleventh contact portion 511, and a twelfth contact portion 512. The top surface contact portions are a fifth contact portion 505, a sixth contact portion 506, a seventh contact portion 507, and an eighth contact portion 508.

[0085] The width of the bottom-side contact portion is greater than the width of the top-side contact portion. The width of the bottom-side contact portion is the maximum width of the bottom-side contact portion (e.g., width W1 of first contact portion 501) in a direction perpendicular to the center line along the extension direction of the coil wiring layer when viewed from the direction of axis AX. There are multiple bottom-side contact portions, namely, first contact portion 501, second contact portion 502, third contact portion 503, fourth contact portion 504, ninth contact portion 509, tenth contact portion 510, eleventh contact portion 511, and twelfth contact portion 512. Therefore, the width of the bottom-side contact portion is the average value of all the measured widths of the bottom-side contact portions. In other words, the width of the bottom side contact portion is the average value of the widths of the first contact portion 501, the second contact portion 502, the third contact portion 503, the fourth contact portion 504, the ninth contact portion 509, the tenth contact portion 510, the eleventh contact portion 511, and the twelfth contact portion 512.

[0086] Similarly, the width of the top surface side contact portion is the maximum width of the top surface side contact portion (for example, width W2 of fifth contact portion 505) in a direction perpendicular to the center line along the extension direction of the coil wiring layer when viewed from the axis AX direction. Because there are multiple top surface side contact portions, namely, fifth contact portion 505, sixth contact portion 506, seventh contact portion 507, and eighth contact portion 508, the width of the top surface side contact portion is the average value of all the measured widths of the top surface side contact portions. In other words, the width of the top surface side contact portion is the average value of the widths of fifth contact portion 505, sixth contact portion 506, seventh contact portion 507, and eighth contact portion 508.

[0087] The width of each contact portion is measured, for example, by polishing the inductor component 1B along the XZ plane and measuring the width of each contact portion.

[0088] According to the above configuration, the width of the bottom surface side contact portion is larger than the width of the top surface side contact portion, thereby improving the strength of the bottom surface side contact portion and preventing damage such as cracks from occurring to the bottom surface side contact portion even if a large stress is applied to the bottom surface side contact portion.

[0089] Preferably, the width of each of all bottom contact portions is greater than the width of each of all top contact portions. Specifically, the width of the first contact portion 501, the second contact portion 502, the third contact portion 503, the fourth contact portion 504, the ninth contact portion 509, the tenth contact portion 510, the eleventh contact portion 511, and the twelfth contact portion 512 is greater than the width of the fifth contact portion 505, the sixth contact portion 506, the seventh contact portion 507, and the eighth contact portion 508, respectively.

[0090] The present disclosure is not limited to the above-described embodiments, and design modifications are possible within the scope of the present disclosure. For example, various combinations of the features of the first to third embodiments may be used. The number of coil wiring layers may be increased or decreased, and the number of via wiring layers may be increased or decreased. The number of bottom-side via wiring layers may be less than the number of top-side via wiring layers.

[0091] The present disclosure includes the following aspects. <1> The base body and a coil provided within the element body and wound spirally along an axis; a first external electrode and a second external electrode provided on the element body and electrically connected to the coil; Equipped with the element body includes a first end face and a second end face facing each other, a first side face and a second side face facing each other, a bottom face connected between the first end face and the second end face and between the first side face and the second side face, and a top face facing the bottom face, the first external electrode and the second external electrode are provided at least on the bottom surface, the axis is parallel to the bottom surface and intersects the first side surface and the second side surface; the coil has a plurality of coil wiring layers stacked along the axis and a plurality of via wiring layers connecting adjacent coil wiring layers in the axial direction, When viewed from the axial direction, the plurality of via wiring layers extend along a spiral direction of the coil, and the plurality of via wiring layers include a bottom surface-side via wiring layer located on the bottom surface side with respect to a center line between the top surface and the bottom surface of the element body, and a top surface-side via wiring layer located on the top surface side with respect to the center line, an inductor component, wherein a contact area between the bottom surface side via wiring layer and the coil wiring layer is larger than a contact area between the top surface side via wiring layer and the coil wiring layer; <2> When viewed from the axial direction, the length of the bottom surface side via wiring layer is longer than the length of the top surface side via wiring layer. <1> The inductor component according to claim 1. <3> When viewed from the axial direction, the coil wiring layer in contact with the bottom side via wiring layer has a bottom side contact portion in contact with the bottom side via wiring layer, and the coil wiring layer in contact with the top side via wiring layer has a top side contact portion in contact with the top side via wiring layer, The width of the bottom surface contact portion is greater than the width of the top surface contact portion. <1> or <2> The inductor component according to claim 1. <4> When viewed from the axial direction, the intervals of the coils in the spiral direction of all the via wiring layers are equal. <1> from <3> 10. An inductor component according to any one of the preceding claims. <5> the number of the bottom surface side via wiring layers is different from the number of the top surface side via wiring layers; <1> from <4> 10. An inductor component according to any one of the preceding claims. <6> the number of the bottom surface side via wiring layers is greater than the number of the top surface side via wiring layers; <1> from <5> 10. An inductor component according to any one of the preceding claims. <7> When viewed from the axial direction, the length of the bottom surface side via wiring layer is 110% or more and 195% or less of the length of the top surface side via wiring layer. <1> from <6> 10. An inductor component according to any one of the preceding claims. <8> the ratio of the number of the bottom surface side via wiring layers to the number of the top surface side via wiring layers is 2:1; When viewed from the axial direction, the length of the bottom surface side via wiring layer is 110% or more and 125% or less of the length of the top surface side via wiring layer. <1> from <6> 10. An inductor component according to any one of the preceding claims. <9> the ratio of the number of the bottom surface side via wiring layers to the number of the top surface side via wiring layers is 4:3; When viewed from the axial direction, the length of the bottom surface side via wiring layer is 180% or more and 195% or less of the length of the top surface side via wiring layer. <1> from <6> 10. An inductor component according to any one of the preceding claims. [Explanation of symbols]

[0092] 1, 1A, 1B inductor components 10 Base 11 Insulating layer 13 First aspect 14 Second aspect 15 First end surface 16 Second end face 17 Bottom 18 Top 20, 20A, 20B coils 20a Winding part 20b 1st drawer 20c 2nd drawer 30 1st external electrode 31 First end section 32 1st bottom part 33 First external electrode conductor layer 40 2nd external electrode 41 Second end section 42 2nd bottom part 43 Second external electrode conductor layer 51 to 58 1st to 8th coil wiring layers 501~512 1st~12th contact part 61-67 1st to 7th via wiring layers 61a~67a Center point AX axis N center line S1~S12 1st~12th contact surface L1~L7 1st to 7th lengths K1~K4 1st to 4th intervals

Claims

1. The base body and a coil provided within the element body and wound spirally along an axis; a first external electrode and a second external electrode provided on the element body and electrically connected to the coil; Equipped with the element body includes a first end surface and a second end surface facing each other, a first side surface and a second side surface facing each other, a bottom surface connected between the first end surface and the second end surface and between the first side surface and the second side surface, and a top surface facing the bottom surface, the first external electrode and the second external electrode are provided at least on the bottom surface, the axis is parallel to the bottom surface and intersects the first side surface and the second side surface; the coil has a plurality of coil wiring layers stacked along the axis and a plurality of via wiring layers connecting adjacent coil wiring layers in the axial direction, When viewed from the axial direction, the plurality of via wiring layers extend along a spiral direction of the coil, and the plurality of via wiring layers include a bottom surface-side via wiring layer located on the bottom surface side with respect to a center line between the top surface and the bottom surface of the element body, and a top surface-side via wiring layer located on the top surface side with respect to the center line, an inductor component, wherein a contact area between the bottom surface side via wiring layer and the coil wiring layer is larger than a contact area between the top surface side via wiring layer and the coil wiring layer;

2. The inductor component according to claim 1 , wherein the length of the bottom surface side via wiring layer is longer than the length of the top surface side via wiring layer when viewed in the axial direction.

3. When viewed from the axial direction, the coil wiring layer in contact with the bottom side via wiring layer has a bottom side contact portion in contact with the bottom side via wiring layer, and the coil wiring layer in contact with the top side via wiring layer has a top side contact portion in contact with the top side via wiring layer, 3. The inductor component according to claim 1, wherein the bottom contact portion has a width greater than a width of the top contact portion.

4. 3. The inductor component according to claim 1, wherein the coils of all the via wiring layers are spaced equally apart in the spiral direction as viewed in the axial direction.

5. The inductor component according to claim 1 , wherein the number of the bottom surface side via wiring layers is different from the number of the top surface side via wiring layers.

6. The inductor component according to claim 5 , wherein the number of the bottom surface side via wiring layers is greater than the number of the top surface side via wiring layers.

7. 3. The inductor component according to claim 1, wherein the length of the bottom surface side via wiring layer is 110% or more and 195% or less of the length of the top surface side via wiring layer when viewed in the axial direction.

8. the ratio of the number of the bottom surface side via wiring layers to the number of the top surface side via wiring layers is 2:1; 3. The inductor component according to claim 1, wherein the length of the bottom surface side via wiring layer is 110% or more and 125% or less of the length of the top surface side via wiring layer when viewed in the axial direction.

9. the ratio of the number of the bottom surface side via wiring layers to the number of the top surface side via wiring layers is 4:3; 3. The inductor component according to claim 1, wherein the length of the bottom surface side via wiring layer is 180% or more and 195% or less of the length of the top surface side via wiring layer when viewed in the axial direction.

Images