inductor

Abstract

The present application provides an inductor with less molten solidification. The inductor has a wiring and a magnetic layer. The magnetic layer has a via hole. The via hole has an inner circumferential surface. A percentage of molten solidification is 10% or less. In a cross section that cuts the via hole, an area of a quadrangle with a first point and a second point and a third point and a fourth point as vertices is obtained, the first point and the second point are located at positions that are separated from a first end edge on a thickness direction side of the inner circumferential surface by 50 μm on one side and the other side of a direction in which the first end edge extends, respectively, based on the first end edge on the thickness direction side of the inner circumferential surface, the third point and the fourth point are located at positions that are separated from a second end edge on the other side of the thickness direction of the inner circumferential surface by 50 μm on one side and the other side of the direction in which the second end edge extends, respectively, based on the second end edge on the other side of the thickness direction of the inner circumferential surface. An area of molten solidification located inside the quadrangle is obtained. A percentage of the area of the molten solidification with respect to the area of the quadrangle is calculated.

Description

TECHNICAL FIELD

[0001] The present application relates to an inductor. BACKGROUND

[0002] In the past, an inductor provided with a wiring and a magnetic layer covering the wiring is known (for example, refer to Patent Literature 1). The magnetic layer of Patent Literature 1 contains magnetic particles. The inductor of Patent Literature 1 is further provided with a slit. The slit is formed in the magnetic layer between two wirings. The slit is formed by laser.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Publication No. 2019-186365 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] However, in order to electrically connect the wiring with an external device, a through hole is sometimes formed in the inductor and a plating layer is formed inside the through hole. The through hole is provided so as to penetrate from the surface of the inductor toward the wiring.

[0008] However, if the through hole is formed by the method of Patent Literature 1, a large amount of fusion solidification of the magnetic particles remains on the inner peripheral surface of the through hole due to the irradiation of the laser to the magnetic layer. In that case, there is a problem that the plating layer cannot be stably formed inside the through hole due to the large amount of fusion solidification.

[0009] The present application provides an inductor with less fusion solidification.

[0010] MEANS FOR SOLVING THE PROBLEMS

[0011] The present application (1) provides an inductor including a wiring and a magnetic layer that buries the wiring and contains magnetic particles, wherein the magnetic layer has a first main surface that is disposed on a thickness direction side with a space from the wiring, a second main surface that is disposed on an opposite side of the first main surface from the wiring with a space in the thickness direction, and a via hole that is provided so as to penetrate from the first main surface toward the wiring, the via hole has an inner peripheral surface that is annular in view of the thickness direction, and a percentage of a molten solid obtained by a method described below is 10% or less. In a cross section that cuts the via hole, an area S0 of a quadrangle with a first point and a second point and a third point and a fourth point as vertices is obtained, the first point and the second point are located at positions that are separated by 50 μm from an end edge on a thickness direction side of the inner peripheral surface in one side and the other side of a direction in which the first main surface extends, respectively, based on the end edge on the thickness direction side of the inner peripheral surface, the third point and the fourth point are located at positions that are separated by 50 μm from an end edge on a thickness direction opposite side of the inner peripheral surface in one side and the other side of the direction in which the first main surface extends, respectively, based on the end edge on the thickness direction opposite side of the inner peripheral surface. An area S1 of the molten solid located inside the quadrangle is obtained. A percentage of the area S1 of the molten solid with respect to the area S0 of the quadrangle (S1 / S0 x 100%) is obtained.

[0012] The inductor has less molten solid. Therefore, it is possible to stably form a conductive member in the via hole.

[0013] The present application (2) is the inductor according to (1), wherein the number of steps of the inner peripheral surface is one or less in one of the via holes.

[0014] In the inductor, the number of steps is one or less. Therefore, it is possible to further stably form a conductive member in the via hole.

[0015] The present application (3) is the inductor according to (1) or (2), wherein the inner peripheral surface has a slope surface in which an opening cross-sectional area of the via hole becomes larger as it approaches the first main surface.

[0016] In the inductor, since the inner peripheral surface has the slope surface in which the opening cross-sectional area of the via hole becomes larger, it is possible to increase an area of a thickness direction side surface of the conductive member if the conductive member is filled in the via hole. Therefore, connection reliability to an external device is excellent.

[0017] The present application (4) is the inductor according to any one of (1) to (3), wherein a portion of a thickness direction side surface of the wiring that is exposed from the via hole is flat in a cross section of a direction in which the wiring extends.

[0018] In this inductor, in a cross section along the first direction, the portion of the thickness direction side surface of the wiring exposed from the via is in a flat shape, and thus the conductive member can be stably formed.

[0019] The inductor (5) according to any one of (1) to (4) is an inductor in which the wiring includes a conductor and an insulating film disposed on a peripheral surface of the conductor, and the insulating film is exposed from the via.

[0020] In this inductor, the insulating film is exposed from the via, and on the other hand, the insulating film covers the conductor, and thus deterioration and damage of the conductor can be suppressed.

[0021] The inductor (6) according to any one of (1) to (5) is an inductor further including a processing stabilization layer filled into the via.

[0022] In this inductor, the processing stabilization layer is filled into the via, and thus stability at the time of processing of the via can be improved.

[0023] The inductor (7) according to (6) is an inductor in which the inner peripheral surface has a second slope surface in which an opening cross-sectional area of the via becomes smaller as the first main surface is approached.

[0024] In this inductor, when the conductive member is provided to the via, the conductive member can be suppressed from falling off from the via based on an anchoring effect.

[0025] The inductor (8) according to any one of (1) to (4) is an inductor in which the wiring includes a conductor and an insulating film disposed on a peripheral surface of the conductor, the insulating film has a protruding end portion protruding inward from an end edge on the other side of the thickness direction of the inner peripheral surface at the via, the inductor further includes a processing stabilization layer disposed on a thickness direction side surface of the protruding end portion and the inner peripheral surface, and the protruding end portion and the processing stabilization layer expose a thickness direction side surface of the conductor.

[0026] In this inductor, the processing stabilization layer is disposed on the thickness direction side surface of the protruding end portion and the inner peripheral surface, and thus stability at the time of processing of them can be improved. On the other hand, since the protruding end portion and the processing stabilization layer expose the thickness direction side surface of the conductor, the conductor can be reliably connected to an external device.

[0027] The inductor (9) according to any one of (6) to (8) is an inductor in which the processing stabilization layer is further disposed on the first main surface.

[0028] In this inductor, since the processing stabilization layer is disposed on the first main surface, the processing stability of the first main surface can be improved.

[0029] The present invention (10) is an inductor according to any one of (1) to (9), wherein the magnetic particles are soft magnetic particles.

[0030] If the magnetic particles are soft magnetic particles, the inductor will have excellent inductance.

[0031] The present invention (11) is an inductor according to any one of (1) to (10), wherein the via has a longest length D1 and a shortest length D2 in a plane direction orthogonal to the thickness direction, and the ratio (D1 / D2) of the longest length D1 to the shortest length D2 is 10 or less.

[0032] In this inductor, since the ratio of the longest length D1 to the shortest length D2 (D1 / D2) is less than 10, a conductive component can be stably formed in the via.

[0033] The effects of the invention

[0034] The inductor of the present invention has less molten solidified material. Therefore, conductive components can be stably formed in the vias. Attached Figure Description

[0035] Figure 1 This is a top view of the first embodiment of the inductor of the present invention.

[0036] Figure 2 yes Figure 1 The inductor shown is a cross-sectional view along the second direction.

[0037] Figure 3 Is with Figure 2 Image processing diagram of SEM photograph of the inductor along the second direction of the corresponding embodiment 1.

[0038] Figure 4 yes Figure 1 The inductor shown is a cross-sectional view along the first direction.

[0039] Figure 5 This is a processed image of a SEM photograph of the inductor of Comparative Example 1 along the second direction.

[0040] Figures 6A-6E yes Figure 2 The diagram shows the manufacturing process and usage of the inductor. Figure 6A This is the process of preparing magnetic laminates. Figure 6B It is the process of forming a barrier layer (Japanese: レジスト). Figure 6C This is the process of forming a through hole. Figure 6DIt is the process of removing the barrier layer. Figure 6E This is a diagram illustrating the use of a conductive component formed in a via.

[0041] Figure 7 yes Figure 2 The example shown is a variation of the inductor.

[0042] Figure 8 yes Figure 1 The example shown is a variation of the inductor.

[0043] Figure 9 yes Figure 2 The example shown is a variation of the inductor.

[0044] Figure 10 yes Figure 2 The example shown is a variation of the inductor.

[0045] Figures 11A-11B This is a variation of the first embodiment. Figure 11A This indicates an inductor with a through-hole having a second slope. Figure 11B This indicates that the inductor also has a processing stabilization layer and a second processing stabilization layer.

[0046] Figure 12 This is a cross-sectional view of the first embodiment of the inductor of the present invention.

[0047] Figure 13 This is a cross-sectional view of the second embodiment of the inductor of the present invention.

[0048] Figure 14 This is a cross-sectional view of the third embodiment of the inductor of the present invention.

[0049] Explanation of reference numerals in the attached figures

[0050] 1. Inductor; 2. Wiring; 3. Magnetic layer; 4. Conductor; 5. Insulating film; 6. First main surface; 7. Second main surface; 9. Inner circumferential surface; 10. Through hole; 11. One side surface; 13. Step; 24. Processing stabilizing layer; 27. Slope; 28. Second slope; 34. One side surface in the thickness direction; 35. Protruding end; 36. One side surface in the thickness direction; M. Molten solidified material; P1. Point 1; P2. Point 2; P3. Point 3; P4. Point 4; E1. First end edge; E2. Second end edge. Detailed Implementation

[0051] Reference Figures 1-4 The first embodiment of the inductor of the present invention will be described below.

[0052] Inductor 1 has a predetermined thickness and a generally flat plate shape. Inductor 1 is longer in a first direction orthogonal to the thickness direction. Inductor 1 has a rectangular shape when viewed from above. Figures 2-4As shown, the inductor 1 has one side 11 and another side 12. The one side 11 and the other side 12 are arranged opposite each other on one side in the thickness direction with a gap between them. The inductor 1 has wiring 2 and a magnetic layer 3.

[0053] like Figure 1 As shown, wiring 2 extends along the first direction. The shape, size, structure, material, and formulation (filler ratio, content ratio, etc.) of wiring 2 are described, for example, in Japanese Patent Application Publication No. 2019-220618, etc. Figure 2 and Figure 3 As shown, wiring 2 has a generally circular shape in cross-sections along the thickness direction and the second direction. The second direction is orthogonal to both the thickness direction and the first direction.

[0054] Wiring 2 includes an outer peripheral surface 14 in the aforementioned cross-section. Preferably, wiring 2 includes a conductor 4 made of a conductor and an insulating film 5 covering the peripheral surface of the conductor 4.

[0055] The magnetic layer 3 has the same external shape as the inductor 1 when viewed from above. The magnetic layer 3 has a sheet shape extending along the first direction. Furthermore, the magnetic layer 3 conceals the wiring 2 when viewed in cross-section. The material of the magnetic layer 3 is a magnetic composition comprising an adhesive and magnetic particles. From the viewpoint of improving the inductance of the inductor 1, the magnetic particles are preferably soft magnetic particles.

[0056] The magnetic composition and the method for forming the magnetic layer 3 have been described in detail, for example, in Japanese Patent Application Publication Nos. 2019-165221 and 2019-165222. The magnetic layer 3 has a first main surface 6, which is an example of a first main surface, a second main surface 7, which is an example of a second main surface, and an outer surface 8.

[0057] like Figures 2-4 As shown, the first main surface 6 forms one side of the magnetic layer 3 in the thickness direction. The first main surface 6 is also one side 11 of the inductor 1. The first main surface 6 is disposed on one side of the thickness direction relative to the wiring 2, spaced apart from the wiring 2. Figure 2 and Figure 3 As shown, the first main surface 6 includes a curved surface corresponding to the wiring 2.

[0058] The second main surface 7 forms the other side of the magnetic layer 3 in the thickness direction. The second main surface 7 is also the other side 12 of the inductor 1. The second main surface 7 is disposed on the other side of the first main surface 6 in the thickness direction, spaced apart from the first main surface 6. The second main surface 7 is disposed on the opposite side of the first main surface 6 relative to the wiring 2. The second main surface 7 includes a curved surface corresponding to the wiring 2.

[0059] like Figure 1 and Figure 2As shown, the outer side surface 8 is two side surfaces of the magnetic layer 3 that are opposite each other at intervals in the second direction. The outer side surface 8 links the both end edges of the first main surface 6 and the both end edges of the second main surface 7 in the second direction, respectively.

[0060] Also, as Figures 1-3 shown, the magnetic layer 3 has a via hole 10. The via hole 10 is provided in the magnetic layer 3 in correspondence with the both end portions of the wiring 2 in the first direction. The two via holes 10 each have a shape that is substantially circular in plan view. The via hole 10 is provided so as to penetrate from a side surface 11 of the inductor 1 toward the wiring 2. The via hole 10 exposes a thickness direction side surface 34 of the insulating film 5. The thickness direction side surface 34 is a portion of the outer peripheral surface 14 of the wiring 2 that is located on the thickness direction side from the center. The via hole 10 has an inner peripheral surface 9 and a bottom surface 17.

[0061] The inner peripheral surface 9 faces the inside of the via hole 10 in the magnetic layer 3. As Figure 1 shown, the inner peripheral surface 9 is annular in plan view (the same meaning as when viewed from the thickness direction, hereinafter the same). Specifically, the inner peripheral surface 9 has a shape that is substantially a circular ring in plan view. As Figure 2 and Figure 3 shown, the inner peripheral surface 9 has a slope surface 27 that makes the opening cross-sectional area of the via hole 10 larger as it approaches the side surface 11. Specifically, the inner peripheral surface 9 is composed of the slope surface 27. The inner peripheral surface 9 has a step 13. The number of steps 13 is, for example, one for each via hole 10.

[0062] The bottom surface 17 faces the via hole 10. The bottom surface 17 is a portion of the outer peripheral surface 14 of the wiring 2. Also, the bottom surface 17 is the thickness direction side surface 34 of the wiring 2. The bottom surface 17 is continuous with the end edge (second end edge E2 described later) on the thickness direction other side of the inner peripheral surface 9. As Figure 1 shown, the bottom surface 17 has a shape that is substantially circular in plan view. Also, as Figure 2 and Figure 3 shown, the bottom surface 17 has a substantially circular arc shape in a cross section along the second direction. Also, as Figure 4As shown, the bottom surface 17 is flat in cross-section along the first direction. The maximum profile height Rz of the bottom surface 17 is, for example, 10 μm or less, preferably 1 μm or less, more preferably 0.1 μm or less, and also, for example, 0.000001 μm or more. On the other hand, the maximum profile height Rz of the cover portion 18 is, for example, 10 μm or less, preferably 1 μm or less, more preferably 0.1 μm or less, and also, for example, 0.000001 μm or more. The maximum profile height Rz is measured, for example, by a laser microscope or the like. The cover portion 18 is the portion of one side surface 34 in the thickness direction covered by the magnetic layer 3. The ratio of the maximum profile height Rz of the bottom surface 17 to the maximum profile height Rz of the cover portion 18 is, for example, less than 2, preferably 1.5 or less, more preferably 1.1 or less, and also, for example, more than 1. If this ratio is lower than the above upper limit, it is possible to suppress excessive roughness of the bottom surface 17 of the via 10 relative to the cover portion 18. Therefore, it is possible to reliably form the conductive component 19 in the via 10.

[0063] The magnetic layer 3 can be a single layer or multiple layers. In the case of multiple layers, for example, it includes a first layer 15 for burying the wiring 2 and two second layers 16. The two second layers 16 are respectively disposed on one side and the other side of the first layer 15 in the thickness direction. The type and / or proportion of magnetic particles in the second layer 16 are different from the type and / or proportion of magnetic particles in the first layer 15.

[0064] Furthermore, in this inductor 1, the percentage of molten solidified material M is less than 10%.

[0065] The percentage of the molten solidified material M can be determined using the following method.

[0066] First, such as Figures 2-4 As shown, in the cross section of the through hole 10, points P1 and P2, and points P3 and P4 are determined. Points P1 and P2 are located 50 μm apart from the first end edge E1 on one side and the other side of the direction extending from the first main surface 6, respectively, with reference to the first end edge E1 on one side of the thickness direction of the inner circumferential surface 9. Points P3 and P4 are located 50 μm apart from the second end edge E2 on one side and the other side of the direction extending from the second end edge E2 on the other side of the thickness direction of the inner circumferential surface 9, respectively.

[0067] The cross section of the through hole 10 can be as follows Figure 2 and Figure 3 The cross-section shown is along the second direction, or it can be as follows: Figure 4 The cross-section shown is along the first direction.

[0068] The first end edge E1 is the angle formed by the inner circumferential surface 9 and the first main surface 6. In the cross-section along the second direction, as...Figure 2 and Figure 3 As shown, if the first main surface 6 is a curved surface, then the direction in which the first main surface 6 extends is the tangential direction at the first end edge E1. On the other hand, in a cross-section along the first direction, as... Figure 4 As shown, if the first main surface 6 is a flat surface, then the direction in which the first main surface 6 extends is along the direction of the first main surface 6, which is the first direction.

[0069] The second edge E2 is the angle formed by the inner peripheral surface 9 and the outer peripheral surface 14 of the wiring 2. The direction that serves as the reference when determining the third point P3 and the fourth point P4 using the second edge E2 as a reference is the same as the direction that serves as the reference when determining the first point P1 and the second point P2. Therefore, the first line segment L1 connecting the first point P1 and the second point P2 is parallel to the second line segment L2 connecting the third point P3 and the fourth point P4. This forms a quadrilateral with vertices at the first point P1, the second point P2, the third point P3, and the fourth point P4. This quadrilateral is a parallelogram, meaning it has two parallel sides (the first line segment L1 and the second line segment L2).

[0070] Next, obtain the area S0 of the quadrilateral.

[0071] Next, the area S1 of the molten solidified material M located inside the quadrilateral is obtained. The molten solidified material M is formed during the fabrication of the via 10 using the manufacturing method described later. Figure 5 A molten solidified material is formed by the melting, aggregation, and solidification of magnetic particles as shown. For example, the molten solidified material M can also be defined as follows: By observing a cross-sectional SEM image, the perimeter of 10 unmelted magnetic particles is calculated, and the average value is determined. Additionally, by observing a cross-sectional SEM image, the area of ​​10 unmelted magnetic particles is calculated, and the average value is determined. An object having a perimeter larger than the average perimeter of the aforementioned magnetic particles and an area larger than the average area of ​​the aforementioned magnetic particles is a molten solidified material.

[0072] Next, the percentage of the area S1 of the molten solidified material relative to the area S0 of the quadrilateral is calculated (S1 / S0×100%).

[0073] like Figure 5 As shown, if the percentage of the molten solidified material M exceeds 10%, the conductive component 19 described later cannot be stably formed inside the through hole 10 due to the molten solidified material M.

[0074] The upper limit of the percentage of molten solidified material M is preferably 7.5%, more preferably 5%, further preferably 2.5%, particularly preferably 1%, even more preferably 0.1%, and still more preferably 0.01%, and the most preferably 0% of the percentage of molten solidified material M.

[0075] ReferenceFigures 6A-6D To illustrate the manufacturing method of inductor 1.

[0076] The manufacturing method of inductor 1 includes a first step and a second step.

[0077] like Figure 6A As shown, in the first step, a magnetic laminate 20 is fabricated. The magnetic laminate 20 is an inductor 1 before the via 10 is formed. The magnetic laminate 20 includes wiring 2 and a magnetic layer 3. The fabrication method of the magnetic laminate 20 is described in detail, for example, in Japanese Patent Application Publication Nos. 2019-165221 and 2019-165222.

[0078] like Figures 6B-6C As shown, in the second step, a via 10 is formed in the magnetic layer 3. For example, a sandblasting method is used to form the via 10. The sandblasting method includes a third step, a fourth step, and a fifth step.

[0079] like Figure 6B As shown, in the third step, a barrier layer 21 is disposed on the first main surface 6. The barrier layer 21 has an opening 22 corresponding to the through hole 10. The opening 22 extends through the barrier layer 21 in the thickness direction. The barrier layer 21 is made of a material that is not easily damaged by collision with the abrasive particles described below. The material of the barrier layer 21 is not particularly limited. Commercially available products can be used for the barrier layer 21, for example, commercially available "dry film resist for sandblasting" can also be used.

[0080] like Figure 6C As shown, in the fourth step, abrasive particles are sprayed toward the portion of the first main surface 6 exposed from the opening 22. An abrasive particle spraying device (not shown) is used for spraying the abrasive particles.

[0081] An abrasive particle ejection device, for example, comprises, in sequence with respect to the flow direction of the abrasive particles, an inlet section, an extension section, a rectifying section, a collecting section, and an ejection nozzle (not shown). The inlet section is connected to both an abrasive particle container and an air container. The extension section diffuses the abrasive particles internally. The rectifying section regulates the flow of the abrasive particles. The collecting section collects the abrasive particles while increasing the flow pressure. The ejection nozzle has multiple nozzles. Each nozzle is a generally circular orifice. The ejection nozzle ejects abrasive particles from the multiple nozzles in a uniform manner. The structure and operating conditions of the abrasive particle ejection device are described, for example, in Japanese Patent Application Publication No. 2015-199131. Commercially available abrasive particle ejection devices can be used.

[0082] Specifically, examples of abrasive particles include alumina, glass microspheres, silicon carbide, silicon nitride, zirconium oxide, and stainless steel. The nozzle diameter is, for example, 0.1 μm or more, preferably 0.5 μm or more, and also, for example, 10000 μm or less, preferably 5000 μm or less. The median particle size of the abrasive particles is, for example, 0.1 μm or more, preferably 0.5 μm or more, and also, for example, 1000 μm or less, preferably 100 μm or less. The injection pressure of the abrasive particles is, for example, 0.01 MPa or more, preferably 0.05 MPa or more, and also, for example, 10 MPa or less, preferably 5 MPa or less.

[0083] In the fourth step, the portion of the first main surface 6 exposed from the opening 22 is ground, and then a through hole 10 is formed in the magnetic layer 3.

[0084] like Figure 6D As shown, in the fifth step, the barrier layer 21 is removed. Specifically, the barrier layer 21 is peeled off from the first main surface 6.

[0085] Therefore, we can obtain the following: Figures 2-4 The inductor 1 shown has wiring 2, magnetic layer 3 and via 10.

[0086] After that, as Figure 6E As shown, the conductive member 19 is formed within the via 10, for example, by plating, specifically by electroplating. Furthermore, before forming the conductive member 19, the portion of the insulating film 5 located at the via 10 is peeled off using a known method. The insulating film 5 can be peeled off by various methods, for example, by laser processing or sandblasting. Also, a seed layer (not shown) is formed before electroplating. Additionally, the conductive member 19 precipitates from the bottom surface 17 of the via 10. Furthermore, the conductive member 19 precipitates along the inner peripheral surface 9 towards one side in the thickness direction. The conductive member 19 is also formed on one side 11 surrounding the via 10. For example, copper or other conductors can be used as the material for the conductive member 19.

[0087] [Effects of the First Embodiment]

[0088] In this inductor 1, the percentage of molten solidified material is low, below 10%, therefore, the amount of molten solidified material is small. Therefore, as... Figure 6E As shown, conductive components 19 can be stably formed.

[0089] Furthermore, in this inductor 1, the inner peripheral surface 9 has a slope 27 that increases in the cross-sectional area of ​​the opening of the through hole 10 as it approaches the first main surface 6. Therefore, if the through hole 10 is filled with the conductive member 19, the area of ​​one side of the conductive member 19 in the thickness direction can be increased. As a result, the connection reliability with external devices is excellent.

[0090] As Figure 4 shown in the cross section along the first direction, the portion of the thickness direction side surface 34 of the wiring 2 exposed from the via hole 10 is in a flat shape, and thus the conductive member 19 can be stably formed.

[0091] In Figures 2-4 the inductor 1 not provided with the conductive member 19 shown, the processing stabilization layer 24 is disposed on the thickness direction side surface of the protruding end portion 35 and the inner circumferential surface 9, and thus the stability at the time of processing thereof can be improved. On the other hand, the protruding end portion 35 covers the lead wire 4, and thus the deterioration and damage of the lead wire 4 can be suppressed.

[0092] In addition, if the magnetic particles are soft magnetic particles, the inductance of the inductor 1 is excellent.

[0093] [Variation of the First Embodiment]

[0094] The number of steps 13 of the inner circumferential surface 9 can be 0 or plural. The number of steps 13 is preferably 1 or less, and more preferably 0. If the number of steps 13 is 1 or less, the conductive member 19 can be more reliably and stably formed. In Figure 7 , the inner circumferential surface 9 without the steps 13 is depicted.

[0095] The shape of the via hole 10 is not limited to a shape that is substantially circular in plan view. As Figure 8 shown, for example, the via hole 10 has a shape that is substantially rectangular in plan view. In this variation, the via hole 10 is longer in the first direction in plan view. The via hole 10 has a longest length D1 and a shortest length D2 in plan view.

[0096] In this variation, the longest length D1 is the distance between the two opposite vertices in the rectangular shape of the via hole 10. The shortest length D2 is the length in the second direction of the via hole 10. The upper limit of the ratio (D1 / D2) of the longest length D1 to the shortest length D2 is, for example, 10, preferably 5, more preferably 3, and further preferably 2. The lower limit of the ratio is, for example, 1.1, and preferably 1.2. Furthermore, in Figure 1 the circular shape of the via hole 10 shown, the longest length D1 and the shortest length D2 are the same. If the ratio (D1 / D2) is as small as 10 or less, the conductive member 19 can be stably formed in the via hole 10.

[0097] The number of wirings 2 can be plural. As Figure 9 shown, the wirings 2 are disposed opposite each other at intervals in the second direction. The plural (for example, two) wirings 2 are parallel in plan view. The via holes 10 are provided in a manner corresponding to the number of wirings 2.

[0098] The shape of the wiring 2 is not limited. As Figure 10As shown, the shape of the wiring 2 can be a shape in which the cross section is substantially rectangular.

[0099] The thickness direction other side surface of the wiring 2 is in contact with the insulating layer 23. The insulating layer 23 extends in the 2nd direction. As the material of the insulating layer 23, for example, an insulating resin such as polyimide is cited.

[0100] In the first embodiment, in the manufacturing method of the inductor 1, a sandblasting method is used, but is not limited thereto. It is preferable to use a sandblasting method. If a sandblasting method is used, generation of the molten solidified substance M can be reduced as much as possible.

[0101] In another modification, as shown in Figure 11A The inner peripheral surface 9 has a slope surface 27 and a 2nd slope surface 28.

[0102] For the slope surface 27, as approaching the one side surface 11, the opening cross-sectional area of the via hole 10 becomes larger.

[0103] The slope surface 27 goes toward the thickness direction one side from the 2nd end edge E2.

[0104] On the other hand, for the 2nd slope surface 28, as approaching the one side surface 11, the opening cross-sectional area of the via hole 10 becomes smaller. The 2nd slope surface 28 reaches the thickness direction one end edge of the slope surface 27 from the 1st end edge El. In this inner peripheral surface 9, the slope surface 27 and the 2nd slope surface 28 are disposed in order toward the thickness direction one side.

[0105] The distance in the 2nd direction between the thickness direction one end edges of the two 2nd slope surfaces 28 is the distance in the 2nd direction between the two 1st end edges El. The ratio of the distance in the 2nd direction between the thickness direction other end edges E3 of the two 2nd slope surfaces 28 to the distance in the 2nd direction between the two 1st end edges El is, for example, 1.1 or more, preferably 1.2 or more, more preferably 1.5 or more, and for example, 3 or less.

[0106] The distance in the 2nd direction between the thickness direction other end edges of the two 2nd slope surfaces 28 is the distance in the 2nd direction between the two thickness direction other end edges E3. The ratio of the distance in the 2nd direction between the thickness direction other end edges E3 of the two 2nd slope surfaces 28 to the distance in the 2nd direction between the two 2nd end edges E2 is, for example, 1.1 or more, preferably 1.2 or more, more preferably 1.5 or more, and for example, 3 or less.

[0107] In producing this via hole 10, for example, the opening portion 22 of the barrier layer 21 shown in Figure 6B is made narrow. Specifically, the diameter of the opening portion 22 is, for example, 300 μm or less, preferably 200 μm or less.

[0108] Therefore, in the fourth step, the abrasive particles collide with the first main surface 6 of the magnetic layer 3 through the narrow opening 22 to grind the magnetic layer 3. However, the abrasive particles tend to remain on the magnetic layer 3 on the other side of the thickness direction around the opening 22. The abrasive particles flow upstream in the jet direction. At this time, the abrasive particles form an inner circumferential surface 9 with a roughly arc-shaped trajectory. Thus, the abrasive particles form an inner circumferential surface 9 with a second slope 28 and a slope 27.

[0109] like Figure 11B As shown, if the conductive member 19 is disposed in the through hole 10, the conductive member 19 will contact the slope 27 and the second slope 28 respectively.

[0110] like Figure 11B As shown, in this inductor 1, when the conductive member 19 is provided in the through hole 10, the conductive member 19 can be prevented from falling off the through hole 10 based on the anchoring effect.

[0111] like Figure 12 As shown, it is also possible that the inner circumferential surface 9 does not have a slope 27, but only a second slope 28.

[0112] Alternatively, the through hole 10 can be provided on one side 11 and the other side 12, but this is not shown in the figure.

[0113] Alternatively, the via 10 can be provided only at one end of the wiring 2 in the first direction within the magnetic layer 3, but this case is not shown.

[0114] [Second Implementation]

[0115] In the second embodiment, the same reference numerals are used for components and processes identical to those in the first embodiment, and detailed descriptions are omitted. Furthermore, in the second embodiment, unless otherwise specified, the same effects as in the first embodiment can be achieved. Moreover, the first and second embodiments can be appropriately combined.

[0116] like Figure 13 As shown, the inductor 1 also includes a processing stabilization layer 24 and a second processing stabilization layer 25.

[0117] A processing stabilizing layer 24 is filled into the via 10. Additionally, the processing stabilizing layer 24 is also disposed on the first main surface 6. The processing stabilizing layer 24 improves the surface workability of the first main surface 6 of the magnetic layer 3, as well as the surface workability of the inner peripheral surface 9 and the via 10. Furthermore, the processing stabilizing layer 24 is also applied when the conductive member 19 is disposed in the via 30 (see below). Figure 14 (And the third embodiment) is an insulating layer that can ensure the insulation between the conductive member 19 and the magnetic layer 3.

[0118] The process stability layer 24 contains a cured product of a thermosetting resin composition. That is, the material of the process stability layer 24 contains a thermosetting resin composition. The thermosetting resin composition contains a thermosetting resin as a necessary component.

[0119] The thermosetting resin contains a main agent, a curing agent, and a curing accelerator.

[0120] As the main agent, for example, an epoxy resin, a silicone resin, or the like is cited, and an epoxy resin is preferably cited. As the epoxy resin, for example, a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a bisphenol S type epoxy resin, a modified bisphenol A type epoxy resin, a modified bisphenol F type epoxy resin, a modified bisphenol S type epoxy resin, a biphenyl type epoxy resin, a difunctional epoxy resin, for example, a phenol novolak type epoxy resin, a cresol novolak type epoxy resin, a trihydroxyphenylmethane type epoxy resin, a tetraphenylol ethane type epoxy resin, a dicyclopentadiene type epoxy resin, or the like, a polyfunctional epoxy resin of three or more functions, for example, a phenol novolak type epoxy resin, a cresol novolak type epoxy resin, a trihydroxyphenylmethane type epoxy resin, a tetraphenylol ethane type epoxy resin, a dicyclopentadiene type epoxy resin, or the like, or the like is cited. These epoxy resins can be used alone or in combination of two or more. A difunctional epoxy resin is preferably cited, and a bisphenol A type epoxy resin is more preferably cited.

[0121] The lower limit of the epoxy equivalent of the epoxy resin is, for example, 10 g / eq., and the upper limit is, for example, 1000 g / eq.

[0122] As the curing agent, if the main agent is an epoxy resin, a phenol resin, an isocyanate resin, or the like is cited. As the phenol resin, for example, a phenol novolak resin, a cresol novolak resin, a phenol aralkyl resin, a phenol biphenyl resin, a dicyclopentadiene type phenol resin, a resol resin, or the like is cited. These phenol resins can be used alone or in combination of two or more. As the phenol resin, a phenol novolak resin, a phenol biphenyl resin is preferably cited. If the main agent is an epoxy resin and the curing agent is a phenol resin, the lower limit of the total of the hydroxyl groups in the phenol resin with respect to one equivalent of the epoxy group in the epoxy resin is, for example, 0.7 equivalent, and preferably 0.9 equivalent, and the upper limit is, for example, 1.5 equivalent, and preferably 1.2 equivalent. Specifically, the lower limit of the mass fraction of the curing agent with respect to 100 mass parts of the main agent is, for example, 1 mass part, and the upper limit is, for example, 50 mass parts.

[0123] As the curing accelerator, it is a catalyst (a heat curing catalyst) that accelerates the curing of the main agent (preferably an epoxy resin curing accelerator), and, for example, an organic phosphorus compound, an imidazole compound such as 2-phenyl-4-methyl-5-hydroxymethylimidazole (2P4MHZ), or the like is cited. The lower limit of the mass fraction of the curing accelerator with respect to 100 mass parts of the main agent is, for example, 0.05 mass part, and the upper limit is, for example, 5 mass parts.

[0124] Further, the thermosetting resin composition can contain, for example, a particle as an arbitrary component. The particle is dispersed in the thermosetting resin. The particle is, for example, at least one particle selected from a group consisting of a first particle and a second particle.

[0125] The first particle has, for example, a substantially spherical shape. A lower limit of a median particle diameter of the first particle is, for example, 1 μm, and preferably 5 μm, and further, an upper limit of the median particle diameter of the first particle is, for example, 250 μm, and preferably 200 μm. The median particle diameter of the first particle can be calculated by a laser diffraction type particle size distribution measuring device. Further, the median particle diameter of the first particle can also be calculated by binarization processing based on cross-sectional observation.

[0126] The material of the first particle is not particularly limited. As the material of the first particle, for example, a metal-based material, an inorganic compound, an organic compound, and the like are exemplified, and in order to increase the coefficient of thermal expansion, a metal-based material, an inorganic compound is preferably exemplified.

[0127] In a case where the processing stabilization layer 24 functions as the inductance increasing layer, a metal-based material is contained in the thermosetting resin composition. As the metal-based material, the magnetic body exemplified in the magnetic layer 3 is exemplified, and an organic iron compound containing iron as a first metal element is more preferably exemplified, and carbonyl iron is further more preferably exemplified.

[0128] In a case where the processing stabilization layer 24 functions as the coefficient of thermal expansion suppressing layer, an inorganic compound is contained in the thermosetting resin composition. As the inorganic compound, for example, an inorganic filler is exemplified, and specifically, silica, alumina, and the like are exemplified, and silica is preferably exemplified.

[0129] Specifically, as the first particle, spherical silica is preferably exemplified, and further, spherical carbonyl iron is preferably exemplified.

[0130] The second particle has, for example, a substantially flat shape. The substantially flat shape includes a substantially plate shape.

[0131] A lower limit of a flatness (degree of flatness) of the second particle is, for example, 8, and preferably 15, and further, an upper limit is, for example, 500, and preferably 450.

[0132] A lower limit of a median particle diameter of the second particle is, for example, 1 μm, and preferably 5 μm, and further, an upper limit of the median particle diameter of the second particle is, for example, 250 μm, and preferably 200 μm.

[0133] The median particle diameter of the second particle can be calculated by the same method as that of the median particle diameter of the first particle.

[0134] A lower limit of an average thickness of the second particle is, for example, 0.1 μm, and preferably 0.2 μm, and further, an upper limit is, for example, 3.0 μm, and preferably 2.5 μm.

[0135] The material of the second particles is, for example, an inorganic compound. As the inorganic compound, for example, a thermally conductive compound such as boron nitride is cited. Thus, it is preferable that, in the case where the processing stabilization layer 24 functions as a thermal conductivity improving layer, the inorganic compound is contained in the thermosetting resin composition.

[0136] Specifically, as the second particles, boron nitride of a flat shape is preferably cited.

[0137] In the thermosetting resin composition, one of the first particles and the second particles is contained, or both the first particles and the second particles are contained.

[0138] The lower limit of the mass fraction of the particles (the first particles and / or the second particles) with respect to 100 mass parts of the thermosetting resin is, for example, 10 mass parts, and is preferably 50 mass parts, and the upper limit is, for example, 2000 mass parts, and is preferably 1500 mass parts. Further, the lower limit of the content ratio of the particles in the cured product is, for example, 10 mass%, and the upper limit is, for example, 90 mass%. In the case where both the first particles and the second particles are contained in the thermosetting resin composition, the lower limit of the mass fraction of the second particles with respect to 100 mass parts of the first particles is, for example, 30 mass parts, and the upper limit is, for example, 300 mass parts.

[0139] Further, since the particles are an arbitrary component in the thermosetting resin composition, the thermosetting resin composition can also not contain the particles.

[0140] On the other hand, the material of the processing stabilization layer 24 can further contain a thermoplastic resin. The lower limit of the mass fraction of the thermoplastic resin with respect to 100 mass parts of the thermosetting resin is, for example, 1 mass part, and the upper limit is, for example, 100 mass parts.

[0141] The lower limit of the thickness of the processing stabilization layer 24 is, for example, 1 μm, and is preferably 10 μm, and the upper limit is, for example, 1000 μm, and is preferably 100 μm. The lower limit of the ratio of the thickness of the processing stabilization layer 24 with respect to the thickness of the inductor 1 is, for example, 0.001, and is preferably 0.005, and is more preferably 0.01, and the upper limit is, for example, 0.5, and is preferably 0.3, and is more preferably 0.1. Further, the thickness of the processing stabilization layer 24 is the shortest length between the first main surface 6 and the thickness direction side surface of the processing stabilization layer 24.

[0142] The second processing stability layer 25 is provided on the other side surface 12 of the inductor 1. The second processing stability layer 25 improves the surface processing property with respect to the other side surface 12 of the inductor 1. The second processing stability layer 25 includes a cured product of a thermosetting resin composition, and the material of the second processing stability layer 25 includes the thermosetting resin composition described in the processing stability layer 24. The lower limit of the thickness of the second processing stability layer 25 is, for example, 1 μm, preferably 10 μm, and the upper limit is, for example, 1000 μm, preferably 100 μm. The lower limit of the ratio of the thickness of the second processing stability layer 25 with respect to the thickness of the inductor 1 is, for example, 0.001, preferably 0.005, more preferably 0.01, and the upper limit is, for example, 0.5, preferably 0.3, more preferably 0.1. Further, the thickness of the second processing stability layer 25 is the shortest length between the second main surface 7 and the other side surface in the thickness direction of the second processing stability layer 25.

[0143] To obtain the inductor 1 of the second embodiment, as shown by the imaginary line of FIG. 6, two processing stability sheets 26 are prepared. The two processing stability sheets 26 are each formed in a sheet shape from the material of the processing stability layer 24 and the second processing stability layer 25. The processing stability sheet 26 preferably includes a B-stage thermosetting resin composition. Further, the above-described material can also be prepared by further compounding a solvent to the above-described thermosetting resin composition and adjusting the above-described material as a varnish. Further, a thermoplastic resin can be further compounded in the material. In this method, the varnish is applied to the surface of a peeling sheet not shown and dried to form the processing stability sheet 26. Figure 13

[0144] Next, the two processing stability sheets 26 and the inductor 1 are pressed from both sides in the thickness direction. Thereafter, they are heated to C-stage the two processing stability sheets 26. Thus, the inductor 1 is provided with the processing stability layer 24 provided on the first main surface 6 of the magnetic layer 3, the inner peripheral surface 9 of the via hole 10, and the thickness direction one side surface 34 of the insulating film 5, and the second processing stability layer 25 provided on the second main surface 7 of the magnetic layer 3.

[0145] [Effects of the Second Embodiment]

[0146] In the inductor 1 of the second embodiment, the processing stability layer 24 is filled to the via hole 10, and thus the stability at the time of the subsequent processing (the third embodiment described later) with respect to the via hole 10 can be improved.

[0147] [Third Embodiment]

[0148] ​In the third embodiment, the same components and processes as those of the first and second embodiments are denoted by the same reference numerals, and detailed description thereof is omitted. In the third embodiment, the same effects as those of the first and second embodiments can be obtained unless otherwise noted. The first through third embodiments can be appropriately combined.

[0149] As shown in FIG. 1, the thickness direction side surface 36 of the lead wire 4 is exposed on the thickness direction side. For example, the thickness direction side surface 36 of the lead wire 4 is exposed from a portion of the insulating film 5 and the processing stabilization layer 24. Figure 14

[0150] The processing stabilization layer 24 has a first covering portion 31 and a second covering portion 32. The first covering portion 31 covers the first main surface 6 following the first main surface 6. The first covering portion 31 is located on the thickness direction side of the first main surface 6. The second covering portion 32 covers the inner circumferential surface 9 following the via hole 10. The second covering portion 32 overlaps the inner circumferential surface 9 when projected along the second direction (or the first direction). In addition, the second covering portion 32 extends along the thickness direction. The thickness direction other end surface of the second covering portion 32 contacts the protruding end portion 35 of the insulating film 5 from the thickness direction side. The thickness direction other end surface of the second covering portion 32 is a surface of the second covering portion 32 located on the side opposite to the side on which the first covering portion 31 is located. The protruding end portion 35 is a portion of the insulating film 5. The protruding end portion 35 has a substantially circular ring shape in plan view. Note that the circular ring shape of the protruding end portion 35 is not depicted in FIG. 1. The protruding end portion 35 exposes a portion of the thickness direction side surface 36 of the lead wire 4 on the inner side thereof. The inner side surface of the protruding end portion 35 is flush with the inner side surface of the second covering portion 32. Figure 14

[0151] Thus, the protruding end portion 35 of the insulating film 5 and the second covering portion 32 of the processing stabilization layer 24 expose the thickness direction side surface 36 of the lead wire 4 toward the thickness direction side.

[0152] The via hole 10 is divided by the second covering portion 32 of the processing stabilization layer 24, the protruding end portion 35 of the insulating film 5, and the thickness direction side surface 36 of the lead wire 4.

[0153] In forming the via hole 10, the processing stabilization layer 24 of the second embodiment is subjected to, for example, perforation processing.

[0154] As the perforation processing, for example, laser processing and the like are cited.

[0155] [Effects of the Third Embodiment]

[0156] ​​In this inductor 1, since the thickness direction side 36 of the wire 4 is exposed from the second cover portion 32 and the protruding end portion 35, if the conductive member 19 is provided on the thickness direction side 36 of the wire 4, the wire 4 can be electrically connected to an external device.

[0157] On the other hand, if the processing stabilizing layer 24 is an insulating layer, the insulation between them can be improved since the processing stabilizing layer 24 is located between the conductive member 19 and the magnetic layer 3.

[0158]

Example

[0159] The following examples and comparative examples further illustrate the present invention. However, the present invention is not limited to any particular example or comparative example. Furthermore, the specific numerical values ​​such as mixing ratios (including proportions), physical property values, and parameters used in the following description can replace the corresponding upper limit values ​​(values ​​defined as "less than" or "less than") or lower limit values ​​(values ​​defined as "above" or "greater than") of the mixing ratios (including proportions), physical property values, and parameters described in the "Specific Embodiments" above.

[0160] Example 1

[0161] [An embodiment corresponding to the first embodiment]

[0162] like Figure 6A As shown, firstly, a magnetic laminate 20 was fabricated. Specifically, a magnetic layer 3, consisting of a first magnetic sheet with a thickness of 100 μm and a second magnetic sheet with a thickness of 125 μm, covered multiple wirings 2 with a radius of 115 μm. Furthermore, the first magnetic sheet comprises 61.5 vol% spherical magnetic powder, 9.6 vol% cresol varnish-type epoxy resin (main agent), 9.6 vol% phenolic resin (curing agent), 0.5 vol% polyether phosphate ester (dispersant), 0.3 vol% imidazole compound (curing accelerator), and 18.5 vol% thermoplastic resin (carboxyl-containing acrylate copolymer). In addition, the second magnetic sheet comprises 55% by volume of flat magnetic particles made of Fe-Si alloy, 11.0% by volume of cresol varnish-type epoxy resin (main agent), 11.0% by volume of phenolic resin (curing agent), 0.4% by volume of polyether phosphate (dispersant), 0.4% by volume of imidazole compound (curing accelerator) and 21.2% by volume of thermoplastic resin (carboxyl-containing acrylate copolymer).

[0163] like Figure 6B As shown, a barrier layer 21 is formed on the first main surface 6 of the insulating film 5. An opening 22 is formed in the barrier layer 21 through a photolithography process. The opening 22 is circular in shape when viewed from above. The diameter of the opening 22 is 250 μm.

[0164] As shown in FIG. 1, a through-hole 10 was formed by a sandblasting method. An inner peripheral surface 9 of the through-hole 10 had a slope surface 27. Figure 6C

[0165] The conditions of the sandblasting method are described below.

[0166] Nozzle diameter: 2 mm

[0167] Material of abrasive particles: alumina

[0168] Median particle diameter of abrasive particles: 14 μm

[0169] Jet speed: 0.4 MPa

[0170] Next, as shown in FIG. 2, the barrier layer 21 was peeled off from the first main surface 6. Figure 6D

[0171] Thus, the inductor 1 was manufactured.

[0172] Example 2

[0173] [Example corresponding to the 2nd embodiment]

[0174] As shown in FIG. 3, the inductor 1 of Example 1 was provided with a processing stabilization layer 24 and a second processing stabilization layer 25. Figure 13 Specifically, first, as shown by the imaginary line of FIG. 4, two processing stabilization sheets 26 were prepared. The processing stabilization sheet 26 was formed by applying a varnish containing 935 parts by mass of spherical silica particles (first particles), 100 parts by mass of a bisphenol A type epoxy resin (a main agent of a thermosetting resin), 106 parts by mass of a phenol resin (a curing agent), 4 parts by mass of an imidazole compound (a curing accelerator), and 10 parts by mass of cyclohexanone (a solvent) and drying it. The content ratio of the silica particles in the processing stabilization sheet 26 was 55% by volume. The thickness of the processing stabilization sheet 26 was 40 μm. The processing stabilization sheet 26 was in a B stage.

[0175] Figure 13 The two processing stabilization sheets 26 and the inductor 1 were pressurized from both sides in the thickness direction. Thereafter, the processing stabilization sheet 26 was B staged.

[0176] Example 3

[0177] [Example corresponding to the 3rd embodiment]

[0178] As shown in FIG. 5, the through-hole 10 was formed in the processing stabilization layer 24 of Example 2.

[0179] As shown in FIG. 5, the through-hole 10 was formed in the processing stabilization layer 24 of Example 2. Figure 14

[0180] ​​​​Specifically, the via hole 10 was formed using a laser device in the process of forming the stabilization layer 24.

[0181] After that, as shown in FIG. 6, after a seed layer (not shown) was formed in the via hole 10 by electroless copper plating, the conductive member 19 was formed by electroplating copper. The conductive member 19 was successfully formed. Figure 6E

[0182] Example 4

[0183] The process was performed similarly to Example 1 except that the diameter of the opening portion 22 was changed to 100 μm. As shown in FIG. 8, the inner peripheral surface 9 had a slope 27 and a second slope 28. Figure 11A

[0184] Further, the distance between the two first end edges El in the second direction was 105 μm, the distance between the two second end edges E2 in the second direction was 85 μm, and the distance between the two second slope 28 in the second direction was 122 μm.

[0185] Comparative Example 1

[0186] In the formation of the via hole, instead of the sandblasting method, laser processing was changed, and the process was performed similarly to Example 1 except for this. The lead wire 4 was exposed by laser processing. Further, the conductive member 19 was attempted to be formed by electroplating copper. However, a defect occurred in the formation of the conductive member 19.

[0187] Evaluation

[0188] SEM observation, proportion of fused solid M, and formation of conductive member

[0189] Cross-sectional SEM observation was performed on each of the examples and comparative examples. An image-processed diagram of the SEM along the second direction of Example 1 is shown in FIG. 9. An image-processed diagram of the SEM along the second direction of Comparative Example 1 is shown in FIG. 10. Figure 3 Figure 5

[0190] Further, the percentage of the fused solid M was calculated. The results are shown in Table 1.

[0191] In addition, the conductive member 19 on the bottom surface 17 and the inner peripheral surface 9 of the via hole 10 was observed by cross-sectional SEM image, and the formation of the conductive member 19 was evaluated according to the following criteria.

[0192] [Good] The conductive member 19 was formed without the fused solid M being interposed.

[0193] [Defective] The conductive member 19 was formed with the fused solid M being interposed.

[0194] [Table 1]​​​​

[0195]

[0196] Further, the application described above is provided as an example of an embodiment of the present application, but this is merely an example and is not to be construed as a limitation. Variations of the present application that will be apparent to those skilled in the art are included within the scope of the foregoing claims.

Claims

1. An inductor provided with a wiring and a magnetic layer that buries the wiring and contains magnetic particles, the inductor characterized by, the magnetic layer having: a first main surface that is disposed on a thickness direction side with respect to the wiring in a manner spaced apart from the wiring; a second main surface that is spaced apart from the first main surface in the thickness direction, the second main surface being disposed on an opposite side of the first main surface with respect to the wiring; and a via hole that is provided penetrating from the first main surface toward the wiring, the via hole having an inner peripheral surface that is annular in view from the thickness direction, a percentage of a molten solidified substance calculated by the following method being 10% or less, that is, in a cross section that cuts the via hole, an area S0 of a quadrangle with a first point and a second point and a third point and a fourth point as vertices is obtained, the first point and the second point being located at positions that are separated by 50 μm from an end edge on a thickness direction side of the inner peripheral surface in a direction in which the first main surface extends on one side and the other side, respectively, with the end edge on the thickness direction side of the inner peripheral surface as a reference, the third point and the fourth point being located at positions that are separated by 50 μm from an end edge on a thickness direction opposite side of the inner peripheral surface in the direction on one side and the other side, respectively, with the end edge on the thickness direction opposite side of the inner peripheral surface as a reference, an area S1 of the molten solidified substance that is located inside the quadrangle is obtained, and a percentage of the area S1 of the molten solidified substance with respect to the area S0 of the quadrangle, that is, S1 / S0 x 100% is calculated.

2. The inductor according to claim 1, characterized in that, in one of the via holes, the number of steps of the inner peripheral surface is one or less.

3. The inductor according to claim 1 or 2, characterized in that, the inner peripheral surface has a slope surface in which an opening cross-sectional area of the via hole becomes larger as it approaches the first main surface.

4. The inductor according to claim 1 or 2, characterized in that, in a cross section in the direction in which the wiring extends, a portion of a thickness direction side face of the wiring that is exposed from the via hole is flat.

5. The inductor according to claim 1 or 2, characterized in that, the wiring is provided with a lead wire and an insulating film that is disposed on a peripheral surface of the lead wire, the insulating film is exposed from the via hole.

6. The inductor according to claim 1 or 2, characterized in that, the inductor is further provided with a processing stabilizing layer that is filled into the via hole.

7. The inductor according to claim 6, characterized in that, the inner peripheral surface has a second slope surface in which an opening cross-sectional area of the via hole becomes smaller as it approaches the first main surface.

8. The inductor according to claim 1 or 2, characterized in that, the wiring is provided with a lead wire and an insulating film that is disposed on a peripheral surface of the lead wire, the insulating film has a protruding end portion that protrudes inward from an end edge on the thickness direction opposite side of the inner peripheral surface at the via hole, the inductor is further provided with a processing stabilizing layer that is disposed on a thickness direction side face of the protruding end portion and the inner peripheral surface, The protruding end portion and the processing stabilization layer expose a thickness direction side surface of the conductor.

9. The inductor according to claim 6, wherein The processing stabilization layer is also provided on the first main surface.

10. The inductor according to claim 1 or 2, wherein The magnetic particles are soft magnetic particles.

11. The inductor according to claim 1 or 2, wherein The via hole has a longest length D1 and a shortest length D2 in a surface direction orthogonal to the thickness direction, A ratio of the longest length D1 to the shortest length D2, D1 / D2, is 10 or less.

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