Inductors and their manufacturing methods

Abstract

This invention provides an inductor that can suppress reductions in installability and operability. The inductor 1 of this invention has a sheet shape. The inductor 1 includes a first wiring 2 and a second wiring 3, and a magnetic layer 4 for embedding them. The magnetic layer 4 has a first main surface 5 and a second main surface 6. The first main surface 5 has a first recess 9. The second main surface 6 has a second recess 12. The ratio (L1 / L2) of the depth L1 of the first recess 9 to the depth L2 of the second recess 12 is 0.67 or more and 1.50 or less.

Description

Technical Field

[0001] This invention relates to an inductor and a method for manufacturing the same. Prior Technology

[0002] An inductor with a sheet-like shape is known, comprising two transversely adjacent wirings and a magnetic layer for embedding them (for example, see Patent Document 1 below). In the inductor described in Patent Document 1, one side of the magnetic layer in the thickness direction has a first opposing portion facing the two wirings, and a first recess between the two opposing portions facing the other side. The other side of the magnetic layer in the thickness direction has a second opposing portion facing the two wirings, and a second recess between the two second opposing portions facing one side. [Previous Technical Documents] [Patent Literature]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-150059 Summary of the Invention

[0004] [The problem the invention aims to solve]

[0005] In Patent Document 1, the first recess is significantly deeper than the second recess. This difference in depth causes the inductor to warp, with its two lateral ends shifting towards one side of its thickness relative to its lateral center. This makes it difficult to mount the inductor onto an external substrate and also makes it difficult to mount electronic components onto the inductor. In other words, it results in reduced inductor mountability.

[0006] Furthermore, there is a problem where the inductor's operability is reduced due to the aforementioned warping.

[0007] This invention provides an inductor that can suppress the reduction in installability and operability, and a method for manufacturing the same. [Technical means to solve the problem]

[0008] The present invention (1) includes an inductor having a sheet shape and comprising: a first wiring and a second wiring adjacent to each other in a direction orthogonal to the thickness direction; and a magnetic layer for embedding the first wiring and the second wiring; wherein the magnetic layer has: a first main surface exposed on one side of the thickness direction; and a second main surface exposed on the other side of the thickness direction; wherein the first main surface has a first recess recessed between a first opposing portion and a second opposing portion, the first opposing portion being... The first wiring is opposite to the second wiring in the thickness direction, and the second opposing portion is opposite to the second wiring in the thickness direction; and the second main surface has a second recess recessed between the third opposing portion and the fourth opposing portion, the third opposing portion is opposite to the first wiring in the thickness direction, and the fourth opposing portion is opposite to the second wiring in the thickness direction; and the ratio (L1 / L2) of the depth L1 of the first recess to the depth L2 of the second recess is 0.67 or more and 1.50 or less.

[0009] In this inductor, the ratio (L1 / L2) of the depth L1 of the first recess to the depth L2 of the second recess is 0.67 or more and 1.50 or less, thus suppressing inductor warping. Therefore, the inductor can be reliably mounted on an external substrate. Furthermore, since inductor warping is suppressed, electronic components can be reliably mounted within the inductor. Therefore, any reduction in inductor mountability is prevented.

[0010] Furthermore, it can suppress the reduction in inductor operability caused by the aforementioned warping.

[0011] Therefore, the inductor exhibits excellent dimensional accuracy in subsequent processing steps and superior positional accuracy during installation.

[0012] The present invention (2) includes an inductor as in (1), wherein the warpage determined in the following measurements is less than 200 μm.

[0013] A sample of the inductor was fabricated with a length of 60 mm and a width of 60 mm. The sample was placed on the water platform with its second main surface facing the surface of the platform. Within a 30 mm long and 30 mm wide region at the center of the inductor, the longest length L3 and the shortest length L4 from the surface of the water platform to the second main surface were determined. The difference between the longest height L3 and the shortest height L4 (L3-L4) was calculated as the warpage.

[0014] In this inductor, the warpage of the difference between the longest height L3 and the shortest height L4 (L3-L4) is less than 200 μm, thus effectively reducing warpage.

[0015] The present invention (3) includes a method for manufacturing an inductor, comprising a step of hot pressing a pressurized laminate, the pressurized laminate comprising magnetic particles, a magnetic sheet comprising a thermosetting resin, and a plurality of wires spaced apart from each other in a direction orthogonal to the thickness direction of the magnetic sheet, the pressurized laminate further comprising a first resin sheet and a second resin sheet clamping the magnetic sheet and the plurality of wires in the thickness direction, wherein in the above step, a fluid flexible sheet, the first resin sheet and the second resin sheet are used, and in the above step, the second resin sheet, the first resin sheet and the fluid flexible sheet are sequentially arranged toward one side of the thickness direction, the tensile storage modulus E' of the second resin sheet at the hot pressing temperature is lower than the tensile storage modulus E' of the first resin sheet at the hot pressing temperature.

[0016] The present invention (4) includes a method for manufacturing an inductor as claimed in claim 3, wherein the tensile storage modulus E' of the second resin sheet at 170°C is lower than the tensile storage modulus E' of the first resin sheet at 170°C.

[0017] The present invention (5) includes a method for manufacturing an inductor as claimed in claim 3 or 4, wherein there are a plurality of magnetic sheets, and in the pressurized laminate, the plurality of magnetic sheets clamp the plurality of wirings in the thickness direction.

[0018] The present invention (6) includes a method of manufacturing an inductor as claimed in any one of claims 3 to 5, wherein, in the above steps, stress deformation of the same degree is generated in the laminated sheet comprising the fluid flexible sheet and the first resin sheet and the second resin sheet by the reaction force from the plurality of wirings and the magnetic sheet. [Effects of the Invention]

[0019] Inductors manufactured using the method of this invention can suppress the reduction in installability and operability. Simple Explanation of the Diagram

[0020] Figure 1 is a cross-sectional view of one embodiment of the inductor of the present invention. Figure 2 shows the orientation of magnetic particles in the magnetic layer of the inductor shown in Figure 1. Figures 3A and 3B are schematic diagrams illustrating the method for measuring the warpage of an inductor. Figure 3A shows warpage with both ends in the first direction positioned on the side further along the thickness direction than the central portion. Figure 3B shows warpage with both ends in the first direction positioned on the side further along the thickness direction than the central portion. Figure 4 is a schematic diagram illustrating the manufacturing method of an inductor. Figure 5 illustrates the steps of placing the pressurized laminate in the hot press apparatus. Figure 6 illustrates the steps involved in forming the decompression space following Figure 5. Figure 7 shows the hot pressing steps performed on the magnetic sheet following Figure 6. Implementation

[0021] <One Implementation Method> An embodiment of the inductor of the present invention will be described with reference to Figures 1 and 2.

[0022] <Inductor 1> The inductor 1 has a sheet shape. The inductor 1 extends in a first direction orthogonal to the thickness direction. The thickness direction is the up-down direction in Figures 1 and 2. The first direction is the left-right (lateral) direction in Figures 1 and 2. The inductor 1 includes a first wiring 2, a second wiring 3, and a magnetic layer 4.

[0023] <Wire 1, Wiring 2 and Wire 2, Wiring 3> The first wiring 2 and the second wiring 3 are adjacent to each other and spaced apart in the first direction. Each of the first wiring 2 and the second wiring 3 is spaced apart in an adjacent direction orthogonal to both the length and thickness directions. The aforementioned length direction is the paper thickness direction in Figures 1 and 2. Of the first wiring 2 and the second wiring 3, the first wiring 2 is located on one side of the first direction. The second wiring 3 is located on the other side of the first direction. Each of the first wiring 2 and the second wiring 3 has a generally circular shape, for example, when viewed in cross-section. The structure and dimensions of each of the first wiring 2 and the second wiring 3 are described, for example, in Japanese Patent Application Publication No. 2020-150057.

[0024] <Magnetic Layer 4> The magnetic layer 4 has the same external shape as the inductor 1. Specifically, the magnetic layer 4 has a sheet shape extending in a first direction. The magnetic layer 4 is used to embed the first wiring 2 and the second wiring 3. The magnetic layer 4 has a first main surface 5 and a second main surface 6.

[0025] The first main surface 5 is exposed on one side of the thickness direction. The first main surface 5 is one side of the inductor 1 in the thickness direction. When projected along the first direction, the first main surface 5 is positioned on one side of the thickness direction relative to the first wiring 2 and the second wiring 3. The first main surface 5 has a first opposing portion 7, a second opposing portion 8, and a first recess 9.

[0026] The first opposing portion 7 faces the first wiring 2 at a distance from one side of the first wiring 2 in the thickness direction. Specifically, the first opposing portion 7 is curved along one side of the first wiring 2 in the thickness direction. The first opposing portion 7 is a first raised portion.

[0027] The second opposing portion 8 is spaced apart from one side of the second wiring 3 in the thickness direction and faces it. Specifically, the second opposing portion 8 is curved along one side of the second wiring 3 in the thickness direction. The second opposing portion 8 is a second raised portion. The second opposing portion 8 is spaced apart from the first opposing portion 7 in the other side of its first direction.

[0028] The first recess 9 is disposed between the first opposing portion 7 and the second opposing portion 8. The first recess 9 is recessed from one end edge of the first opposing portion 7 in a first direction and from one end edge of the second opposing portion 8 in a first direction towards the other side in the thickness direction. The depth L1 of the first recess 9 is not limited as long as the following ratio (L1 / L2) is within a desired range. The depth L1 is, for example, 1 μm or more, and, for example, 500 μm or less. The depth L1 of the first recess 9 is the distance between the portion of the first opposing portion 7 and the second opposing portion 8 disposed on the far side in the thickness direction and the portion of the first recess 9 disposed on the far side in the thickness direction.

[0029] The second main surface 6 is exposed on the other side in the thickness direction. The second main surface 6 is the other side of the inductor 1 in the thickness direction. When projected along the first direction, the second main surface 6 is disposed on the other side in the thickness direction relative to the first wiring 2 and the second wiring 3. The second main surface 6 has a third opposing portion 10, a fourth opposing portion 11, and a second recess 12.

[0030] The third opposing portion 10 faces the first wiring 2 at a distance from the other side in the thickness direction. Specifically, the third opposing portion 10 is bent along the other side in the thickness direction of the first wiring 2. The third opposing portion 10 is a third raised portion. In the thickness direction, the third opposing portion 10 is disposed on the opposite side of the first opposing portion 7 relative to the first wiring 2.

[0031] The fourth opposing portion 11 faces the second wiring 3 at a distance from the other side in the thickness direction. Specifically, the fourth opposing portion 11 is curved along the other side in the thickness direction of the second wiring 3. The fourth opposing portion 11 is a fourth raised portion. In the thickness direction, the fourth opposing portion 11 is disposed on the opposite side of the second opposing portion 8 relative to the second wiring 3. In the first direction, the fourth opposing portion 11 is spaced apart from the other side of the third opposing portion 10.

[0032] The second recess 12 is disposed between the third opposing portion 10 and the fourth opposing portion 11. The second recess 12 is recessed from one end edge of the third opposing portion 10 in the first direction and one end edge of the fourth opposing portion 11 in the first direction toward one side in the thickness direction. The depth L2 of the second recess 12 is not limited as long as the ratio (L1 / L2) described below is within the desired range. The depth L2 is, for example, 1 μm or more, and, for example, 500 μm or less. The depth L2 of the second recess 12 is the distance between the portion of the third opposing portion 10 and the fourth opposing portion 11 disposed on the opposite side in the thickness direction and the portion of the second recess 12 disposed on the side furthest in the thickness direction.

[0033] The ratio (L1 / L2) of the depth L1 of the first recess 9 to the depth L2 of the second recess 12 is 0.67 or more and 1.50 or less. If the ratio is less than 0.67 or more than 1.50, the warping of the inductor 1 will increase.

[0034] The ratio (L1 / L2) of the depth L1 of the first recess 9 to the depth L2 of the second recess 12 is preferably 0.75 or more, more preferably 0.85 or more, and even more preferably 0.90 or more. As long as the above ratio is above the lower limit, warping of the two ends 13 in the first direction that are disposed on the side further in the thickness direction than the central portion 14 can be reduced (see Figure 3B).

[0035] The ratio (L1 / L2) of the depth L1 of the first recess 9 to the depth L2 of the second recess 12 is preferably 1.30 or less, more preferably 1.20 or less, and even more preferably 1.10 or less. As long as the above ratio is below the above upper limit, warping of the two ends 13 in the first direction disposed on the side further in the thickness direction than the central portion can be reduced (see Figure 3A).

[0036] Furthermore, the difference between the depth L1 of the first recess 9 and the depth L2 of the second recess 12 is, for example, 50 μm or less, preferably 20 μm or less, even more preferably 10 μm or less, particularly preferably 5 μm or less, and most preferably 2 μm or less. The difference is |L1-L2|. As long as the difference is below the above upper limit, the warping of the inductor 1 can be suppressed.

[0037] The material and properties of the magnetic layer 4 are described, for example, in Japanese Patent Application Publication No. 2020-150057. Specifically, the magnetic layer 4 contains magnetic particles and resin. Examples of magnetic particles include carbonyl iron powder and Fe-Si alloy. Examples of the shape of the magnetic particles include spherical and generally flat (plate-shaped) shapes. Spherical carbonyl iron powder is preferred as a magnetic particle. The resin includes, for example, thermosetting resin.

[0038] The magnetic layer 4 can be a single layer or multiple layers. When the magnetic layer 4 is multiple layers, it is preferable that the magnetic layer 4 contains spherical magnetic particles.

[0039] When the magnetic layer 4 is multilayered, the magnetic layer 4 may include, for example, a first magnetic layer 15, a second magnetic layer 16, and a third magnetic layer 17. In this embodiment, the third magnetic layer 17, the first magnetic layer 15, and the second magnetic layer 16 are arranged sequentially toward one side of the thickness direction.

[0040] The first magnetic layer 15 contacts the outer peripheral surfaces of the first wiring 2 and the second wiring 3 for embedding them. As shown in Figure 2, the first magnetic layer 15 preferably contains spherical magnetic particles. This provides excellent DC overlap characteristics for the inductor 1. The first magnetic layer 15 has one side and another side spaced apart from each other in the thickness direction.

[0041] The second magnetic layer 16 is disposed on one side of the first magnetic layer 15 along its thickness direction. The second magnetic layer 16 includes the aforementioned first main surface 5. Preferably, the second magnetic layer 16 contains flat magnetic particles. The flat magnetic particles can be aligned according to the curved shapes of the first opposing portion 7 and the second opposing portion 8. Therefore, the inductance of the inductor 1 can be improved.

[0042] The third magnetic layer 17 is disposed on the opposite side of the first magnetic layer 15 in the thickness direction. The third magnetic layer 17 includes the aforementioned second main surface 6. Preferably, the third magnetic layer 17 contains flat magnetic particles. The flat magnetic particles can be aligned according to the curved shapes of the third opposing portion 10 and the fourth opposing portion 11. Therefore, the inductance of the inductor 1 can be improved.

[0043] <Inductor Properties> The warpage of inductor 1 determined in the following measurements is, for example, 250 μm or less, preferably 200 μm or less, more preferably 150 μm or less, even more preferably 100 μm or less, particularly preferably 75 μm or less, further preferably 50 μm or less, and even more preferably 30 μm or less. As long as the warpage of inductor 1 is below the above-mentioned upper limit, the warpage of inductor 1 can be reliably reduced.

[0044] <Determination of Warpage in Inductor 1> A sample 18 is fabricated by machining the inductor 1 to a size of 60 mm in length and 60 mm in width. As shown in Figures 3A and 3B, the sample 18 is positioned on the water platform 19 with its second main surface 6 facing the surface 20 of the water platform 19. In the central region 21 of the inductor 1 (30 mm in length and 30 mm in width), the longest length L3 and the shortest length L4 from the surface 20 of the water platform 19 to the first main surface 5 are calculated. The difference between the highest height L3 and the lowest height L4 (L3-L4) is calculated as the warpage.

[0045] Figure 3A depicts the curvature of the two ends 13 of sample 18 relative to the central region 21 on the opposite side of the thickness direction, i.e., a roughly inverted U-shaped curvature. In this case, the central region 21 and the surface 20 of the platform 19 are separated in the vertical direction. In this case, L3 is the distance from the surface 20 of the platform 19 to the central portion 14 of the first main surface 5 of the central region 21. L4 is the distance from the surface 20 of the platform 19 to the end of the first main surface 5 of the central region 21.

[0046] In contrast, Figure 3B depicts a bend, roughly U-shaped bend, of the two ends 13 of sample 18 relative to the central region 21 on the opposite side of the thickness direction. In this case, the central region 21 includes a portion that contacts the surface 20. In this case, L3 is the distance from the surface 20 of the platform 19 to the end of the first main surface 5 of the central region 21. L4 is the distance from the surface 20 of the platform 19 to the central portion 14 of the first main surface 5 of the central region 21. More specifically, since the aforementioned portion contacts the surface 20, L4 is the thickness T of the central portion 14.

[0047] The manufacturing method of inductor 1 is not limited. For example, as shown in Figure 4, a method for manufacturing inductor 1 using first wiring 2, second wiring 3, and magnetic sheet 30 can be exemplified. Furthermore, in this manufacturing method, first resin sheet 25, second resin sheet 26, and flowable flexible sheet 81 are used. Specifically, in the following hot pressing step, first resin sheet 25, second resin sheet 26, and flowable flexible sheet 81 are used.

[0048] The magnetic sheet 30 may be single or multiple. The magnetic sheet 30 is disposed on one side and / or the other side of the thickness direction relative to the first wiring 2 and the second wiring 3.

[0049] When there are multiple magnetic sheets 30, each magnetic sheet 30 may include, for example, a first sheet 31, a second sheet 32, and a third sheet 33. The first sheet 31 is, for example, a magnetic sheet used to form a first magnetic layer 15 (see Figures 1 and 2). The second sheet 32 ​​is a magnetic sheet used to form a second magnetic layer 16 (see Figures 1 and 2). The third sheet 33 is a magnetic sheet used to form a third magnetic layer 17 (see Figures 1 and 2). Each of the first sheet 31, the second sheet 32, and the third sheet 33 may be singular or multiple. The magnetic sheet 30 comprises the magnetic composition described in Japanese Patent Application Publication No. 2020-150057. Furthermore, in the magnetic composition forming the magnetic sheet 30, the thermosetting resin is stage B.

[0050] When there are multiple first sheets 31, the second sheet 32, one first sheet 31, the first wiring 2 and the second wiring 3, another first sheet 31, and the third sheet 33 are sequentially laminated towards the downstream side of the pressure direction. The pressure direction is the up-down direction shown in Figures 5 to 7.

[0051] Both the first resin sheet 25 and the second resin sheet 26 are buffer sheets used in hot pressing but not included in the inductor 1, and are release sheets. Furthermore, the first resin sheet 25, the second resin sheet 26, and the flowable soft sheet 81 also have heat resistance and conformability.

[0052] The first resin sheet 25 is disposed on one side of the thickness direction relative to the first wiring 2 and the second wiring 3. When there are multiple magnetic sheets 30, the first resin sheet 25 is disposed on the opposite side of the first wiring 2 and the second wiring 3, relative to a first sheet 31 and a second sheet 32. The tensile storage modulus E' of the first resin sheet 25 at 170°C is, for example, 1×10⁵ Pa or more, preferably 2×10⁵ Pa or more, more preferably 1×10⁸ Pa or more, particularly preferably 2×10⁸ Pa or more, and, for example, 1×10¹⁰ Pa or less, preferably 5×10⁹ Pa or less. The tensile storage modulus E' of the first resin sheet 25 can be a catalog value or can be measured. The temperature "170°C" for the tensile storage modulus E' is included in the temperature range of hot pressing.

[0053] The second resin sheet 26 is disposed on the opposite side of the first resin sheet 25 relative to the first wiring 2 and the second wiring 3. That is, the second resin sheet 26 is used to be disposed on the opposite side in the thickness direction relative to the first wiring 2 and the second wiring 3. When there are multiple magnetic sheets 30, the second resin sheet 26 is disposed on the opposite side of the first wiring 2 and the second wiring 3 relative to another first sheet 31 and another third sheet 33.

[0054] The second resin sheet 26 is, for example, softer than the first resin sheet 25. If the second resin sheet 26 and the first resin sheet 25 have the same hardness (or tensile storage modulus E' as described below), then the depth L1 of the first recess 9 of the first main surface 5, which is softly supported by the first resin sheet 25 by the flowable soft sheet 81 described below, is significantly deeper than the depth L2 of the second recess 12. However, if, as described above, the second resin sheet 26 is softer than the first resin sheet 25, then, like the first resin sheet 25 softly contacted by the flowable soft sheet 81, the second resin sheet 26 can softly contact the second main surface 6, so the depth L2 of the second recess 12 can be set to the same degree as the depth L1 of the first recess 9.

[0055] The tensile storage modulus E' of the second resin sheet 26 at 170°C is, for example, 1×10⁵ Pa or more, preferably 1×10⁶ Pa or more, and also, for example, 1×10⁹ Pa or less, preferably 1×10⁸ Pa or less. The tensile storage modulus E' of the second resin sheet 26 can be a catalog value or can be measured. The tensile storage modulus E' of the second resin sheet 26 at 170°C is preferably lower than the tensile storage modulus E' of the first resin sheet 25 at 170°C.

[0056] When the tensile storage modulus E' of the second resin sheet 26 at 170°C is lower than the tensile storage modulus E' of the first resin sheet 25 at 170°C, the ratio (L1 / L2) of the depth L1 of the first recess 9 to the depth L2 of the second recess 12 can be set to 1.50 or less.

[0057] The ratio of the tensile storage modulus E' of the first resin sheet 25 at 170°C to the tensile storage modulus E' of the second resin sheet 26 at 170°C is, for example, greater than 1, preferably greater than 2, more preferably greater than 3, even more preferably greater than 4, particularly preferably greater than 5, and most preferably greater than 7. The above ratio is, for example, 10,000 or less, preferably less than 1,000, more preferably less than 100, and even more preferably less than 20. As long as the above ratio is greater than or equal to the lower limit or less than the upper limit, an inductor 1 with reduced warpage can be manufactured.

[0058] Furthermore, when each of the first resin sheet 25 and the second resin sheet 26 is a plurality of layers, the lowest value among the plurality of layers is set as the tensile storage modulus E'. The layer having the lowest tensile storage modulus E' follows the magnetic layer 4.

[0059] The thicknesses of the first resin sheet 25 and the second resin sheet 26 are not limited as long as the following ratio is met: The ratio of the thickness of the first resin sheet 25 to the thickness of the second resin sheet 26 is, for example, 0.01 or more, preferably 0.1 or more, more preferably 0.5 or more, and, for example, 2 or less, preferably 1 or less, more preferably less than 1, and even more preferably 0.8 or less. As long as the above ratio is above or below the lower limit or below the upper limit, the warpage of the inductor 1 can be further reduced. When the first resin sheet 25 is multilayered, the thickness of the first resin sheet 25 is the sum of the thicknesses of the multiple layers. When the second resin sheet 26 is multilayered, the thickness of the second resin sheet 26 is the sum of the thicknesses of the multiple layers.

[0060] The first resin sheet 25 and the second resin sheet 26 are made of resin. The resin is not limited. Examples of resins include polyester, polyolefins, and fluoropolymers. Examples of polyesters include polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). Polyesters include special polyesters. Examples of polyolefins include polyethylene, polypropylene, and polymethylpentene (TPX). The first resin sheet 25 and the second resin sheet 26 are respectively non-porous and / or porous.

[0061] The first resin sheet 25 is a single layer or multiple layers. The second resin sheet 26 is a single layer or multiple layers.

[0062] The flexible sheet 81 is disposed on one side of the thickness direction relative to the first resin sheet 25. The flexible sheet 81 is disposed on the opposite side of the first sheet 31 and the second sheet 32 ​​relative to the first resin sheet 25.

[0063] The material of the fluid soft sheet 81 is not limited as long as it exhibits fluidity and softness upon hot pressing. Examples of materials for the fluid soft sheet 81 include gels or soft elastomers. The material of the fluid soft sheet 81 can also be commercially available products, such as the αGEL series (manufactured by Taica) and the Riken Elastomer series (manufactured by RIKEN TECHNOS). The thickness of the fluid soft sheet 81 is not limited. The lower limit of the thickness of the fluid soft sheet 81 is, for example, 1 mm, preferably 2 mm; and the upper limit of the thickness of the fluid soft sheet 81 is, for example, 1,000 mm, preferably 100 mm.

[0064] As shown in Figure 4, the laminated sheet 28 comprising the flowable flexible sheet 81 and the first resin sheet 25 has, for example, the same softness (hardness) as the second resin sheet 26. Specifically, the tensile storage modulus E' of the laminated sheet 28 comprising the flowable flexible sheet 81 and the first resin sheet 25 at 170°C is, for example, similar to the tensile storage modulus E' of the second resin sheet 26 at 170°C.

[0065] Next, referring to Figures 5 to 7, we will describe a manufacturing method using a hot pressing device 50 as an example of a manufacturing method for inductor 1.

[0066] The inductor 1 is manufactured by hot pressing a magnetic sheet 30, a first wiring 2 and a second wiring 3 with a fluid flexible sheet 81, a first resin sheet 25 and a second resin sheet 26 in a hot pressing device 50.

[0067] The hot pressing device 50 is, for example, a pressure equalization device that can perform equal hot pressing (pressure equalization) on the magnetic sheet 30, the first wiring 2 and the second wiring 3 (see Figure 5). The hot pressing device 50 includes a first mold 73, a second mold 74, an inner frame member 75, an outer frame member 76, and a fluid and flexible sheet 81.

[0068] In this example, the hot pressing device 50 is configured such that the second mold 74, the inner frame member 75, and the outer frame member 76 can approach and pressurize (closely contact) the first mold 73. Furthermore, the first mold 73 cannot move in the pressing direction of the hot pressing device 50.

[0069] The first mold 73 has a generally plate-like shape. The first mold 73 has a first pressure surface 61 facing the second mold 74 described below. The first pressure surface 61 extends in a direction orthogonal to the pressure direction (surface direction). The first pressure surface 61 is flat. Furthermore, the first mold 73 includes a heater (not shown).

[0070] The second mold 74 is spaced apart from the first mold 73 in the pressing direction. The second mold 74 is movable relative to the first mold 73 in the pressing direction. The second mold 74 has a generally plate shape smaller than the first mold 73. Specifically, when projected in the pressing direction, the second mold 74 is contained within the first mold 73. More specifically, when projected in the pressing direction, the second mold 74 overlaps with the central portion of the first mold 73 in the surface direction. The second mold 74 has a second pressing surface 62 facing the central portion of the first pressing surface 61 of the first mold 73 in the surface direction. The second pressing surface 62 extends in the surface direction. The second pressure surface 62 is parallel to the first pressure surface 61. Also, the second mold 74 includes a heater (not shown).

[0071] The inner frame member 75 surrounds the second mold 74. Specifically, although not shown, the inner frame member 75 surrounds the entire circumference of the second mold 74. Furthermore, the inner frame member 75 and the peripheral ends of the first mold 73 are spaced apart in the pressing direction. That is, the inner frame member 75 and the peripheral ends of the first mold 73 are spaced apart and arranged facing each other in the pressing direction. The inner frame member 75 integrally has a third pressing surface 98 facing the peripheral end of the first pressing surface 61, and an inner surface 99 facing inward. The inner frame member 75 is movable relative to the first mold 73 in the pressing direction. On the other hand, the inner frame member 75 is movable together with the second mold 74 in the pressing direction.

[0072] The outer frame member 76 surrounds the inner frame member 75. Specifically, although not shown, the outer frame member 76 surrounds the entire circumference of the inner frame member 75. Furthermore, the outer frame member 76 and the peripheral end of the first mold 73 are spaced apart in the pressing direction. That is, the outer frame member 76 and the peripheral end of the first mold 73 are spaced apart and arranged facing each other in the pressing direction. The outer frame member 76 integrally has a contact surface 82 facing the peripheral end of the first pressing surface 61 and an inner cavity surface 83 facing inward. The outer frame member 76 is movable relative to both the first mold 73 and the inner frame member 75 in the pressing direction.

[0073] Furthermore, the outer frame member 76 has an exhaust port 77. The upstream end of the exhaust port 77 faces the inner surface 83 of the cavity. The exhaust port 77 is connected to the vacuum pump 78 via an exhaust line 79. Moreover, the exhaust line 79 is always closed.

[0074] The flexible sheet 81 is not mounted on the pressurized laminate 40 described below, but is pre-mounted on the hot press 50. The flexible sheet 81 is disposed on the second pressurizing surface 62 of the second mold 74. Furthermore, the flexible sheet 81 is also disposed on the inner side surface 99 of the inner frame member 75. More specifically, the flexible sheet 81 contacts the entire surface of the second pressurizing surface 62 and the downstream portion of the inner side surface 99 in the pressurizing direction. The inner frame member 75 is movable relative to the flexible sheet 81 in the pressurizing direction.

[0075] The hot pressing device 50 is described in detail, for example, in Japanese Patent Application Publication No. 2004-296746. Furthermore, commercially available products can be used as the hot pressing device 50. For example, the DRY LAMINATOR series manufactured by Nikkiso Corporation can be used as the hot pressing device 50.

[0076] In this method, as shown in Figure 5, a pressurizing laminate 40 is first prepared and placed in a hot pressing device 50. The pressurizing laminate 40 includes a first wiring 2, a second wiring 3, a magnetic sheet 30, a first resin sheet 25, and a second resin sheet 26. Specifically, in the pressurizing laminate 40, the second resin sheet 26, the third sheet 33, another first sheet 31, the first wiring 2 and the second wiring 3, the first sheet 31, the second sheet 32, and the first resin sheet 25 are arranged sequentially on one side in the thickness direction.

[0077] In order to prepare the pressurized laminate 40, firstly, the third sheet 33 and another first sheet 31 are sequentially arranged on one side of the thickness direction of the second resin sheet 26.

[0078] Next, the first wiring 2 and the second wiring 3 are arranged on one side of the thickness direction of the other first sheet 31.

[0079] Subsequently, a first sheet 31 and a second sheet 32 ​​are sequentially arranged on the first wiring 2 and the second wiring 3.

[0080] Then, the first resin sheet 25 is disposed on one side of the thickness direction of the second sheet 32.

[0081] Therefore, a pressurized laminate 40 is prepared.

[0082] Next, the prepared pressurized laminate 40 is placed in the hot press device 50. Specifically, the second resin sheet 26 is placed on the first pressing surface 61 of the first mold 73. Furthermore, the first resin sheet 25 in the pressurized laminate 40 faces the fluid and flexible sheet 81.

[0083] Subsequently, as shown by the arrow in Figure 5 and Figure 6, the outer frame component 76 is brought into contact with the first mold 73 to form a decompression space 85.

[0084] Specifically, the outer frame member 76 is pressed against the periphery of the first pressing surface 61 of the first mold 73. Thereby, the contact surface 82 of the outer frame member 76 and the periphery of the first pressing surface 61 of the first mold 73 are in close contact (preferably under pressure). This forms a sealed space 84.

[0085] The enclosed space 84 is separated by the inner side 83 of the cavity of the outer frame member 76, the third pressure surface 98 of the inner frame member 75, the fluid and flexible sheet 81, and the first pressure surface 61 of the first mold 73.

[0086] The pressure of the outer frame member 76 on the first mold 73 is set to a degree that ensures the airtightness (not to the outside) of the pressure relief space 85 by means of the close contact between the contact surface 82 and the first pressure surface 61, specifically, it is 0.1 MPa or more and 20 MPa or less.

[0087] This creates a sealed space 84 between the first mold 73, the outer frame component 76, and the second mold 74. The sealed space 84 is isolated from the outside. However, the exhaust pipe 79 can lead to the sealed space 84.

[0088] On the other hand, the first resin sheet 25 and the fluid and flexible sheet 81 are still spaced apart in the pressure direction.

[0089] Then, the pressure in the sealed space 84 is reduced to form a depressurization space 85.

[0090] Specifically, the vacuum pump 78 is driven, and then the exhaust line 79 is opened. This reduces the pressure in the sealed space 84 connected to the exhaust port 77. Thus, the sealed space 84 becomes a pressure-reducing space 85.

[0091] The upper limit of the difference between the air pressure in the environment where the hot press device 50 is installed and the air pressure in the decompression space 85 (and the exhaust pipe 79) is, for example, 1,000,000 Pa, and the lower limit of the above difference is, for example, 1 Pa.

[0092] Subsequently, as shown by the arrow in Figure 6 and Figure 7, the second mold 74 and the inner frame component 75 are brought close to the first mold 73, and the magnetic sheet 30, the first wiring 2, and the second wiring 3 are hot-pressed through the fluid flexible sheet 81, the first resin sheet 25, and the second resin sheet 26.

[0093] The second mold 74 is moved in the pressure direction. As a result, the fluid and flexible sheet 81 approaches the first resin sheet 25 as the second mold 74 and the inner frame member 75 move. The inner frame member 75 is linked to the second mold 74.

[0094] Therefore, the fluid flexible sheet 81 softly contacts the entire material except for the peripheral end on the upstream side of the first resin sheet 25 in the pressure direction. At this time, due to its fluidity and flexibility, the fluid flexible sheet 81, together with the first resin sheet 25, is in close contact with the shape of the first wiring 2 and the second wiring 3. At this time, the inner frame member 75 moves in conjunction with the second mold 74, so a portion of the inner side surface 99 of the inner frame member 75 contacts the peripheral side surface of the fluid flexible sheet 81. The third pressure surface 98 of the inner frame member 75 contacts the peripheral end of the first pressure surface 61 of the first mold 73.

[0095] Then, the second mold 74 is hot-pressed toward the first mold 73.

[0096] The lower limit of the hot pressing pressure is, for example, 0.1 MPa, preferably 1 MPa, more preferably 2 MPa, and the upper limit is, for example, 30 MPa, preferably 20 MPa, more preferably 10 MPa. The lower limit of the heating temperature is, for example, 100℃, preferably 110℃, more preferably 130℃, and the upper limit is, for example, 200℃, preferably 185℃, more preferably 175℃. The lower limit of the heating time is, for example, 1 minute, preferably 5 minutes, more preferably 10 minutes, and the upper limit is, for example, 1 hour, preferably 30 minutes.

[0097] Therefore, equal pressure is applied to the magnetic sheet 30, the first wiring 2, and the second wiring 3 from both sides of the thickness direction and the surface direction of the magnetic sheet 30. In short, the magnetic sheet 30 and the first and second wirings 2 are subjected to uniform pressure.

[0098] Thus, the magnetic sheet 30 flows in a manner that allows the first wiring 2 and the second wiring 3 to be embedded.

[0099] Furthermore, the peripheral side of the magnetic sheet 30 is pressurized from the side (outer side) towards the inner side by the fluid and flexible sheet 81. Therefore, the outward flow of the peripheral side of the magnetic sheet 30 can be suppressed.

[0100] In the aforementioned hot pressing, the first resin sheet 25 is harder than the second resin sheet 26. However, it is supported by a soft and fluid sheet 81, thus flexibly supporting (contacting) the second main surface 6 of the inductor 1. Conversely, the second resin sheet 26 is softer than the first resin sheet 25, and therefore can support (contact) the first recess 9 of the inductor 1 with the same degree of softness as the second resin sheet 26. Therefore, an inductor 1 comprising the first recess 9 and the second recess 12 having the aforementioned ratio can be manufactured.

[0101] Specifically, when the tensile storage modulus E' of the laminated sheet 28 containing the flexible sheet 81 and the first resin sheet 25 at 170°C is similar to that of the second resin sheet 26 at 170°C, during the aforementioned hot pressing, the laminated sheet 28 containing the flexible sheet 81 and the first resin sheet 25, and the second resin sheet 26, respectively, experience stress deformation of the same degree due to the reaction forces from the first wiring 2 and the second wiring 3 and the magnetic sheet 30. Consequently, the two sheet pressing surfaces 29A and 29B follow the shape of the first wiring 2 and the second wiring 3 and the magnetic sheet 30, which are the objects of pressing. Therefore, the ratio (L1 / L2) of the depth L1 of the first recess to the depth L2 of the second recess can be set within a specific range (specifically, 0.67 or more and 1.50 or less). Furthermore, the pressing surface 29A of the sheet under hot pressing is the other side of the first resin sheet 25 in the thickness direction. The pressing surface 29B of the sheet under hot pressing is one side of the second resin sheet 26 in the thickness direction.

[0102] Furthermore, the flow of the aforementioned magnetic sheet 30 is caused by the flow of the thermosetting resin in stage B generated by the heating of the heaters of the first mold 73 and the second mold 74, and the flow of the thermoplastic resin as needed.

[0103] By further heating with the aforementioned heater, the thermosetting resin becomes stage C. That is, a magnetic layer 4 is formed, which contains magnetic particles and a hardened body (stage C body) of thermosetting resin.

[0104] In this way, an inductor 1 is manufactured having a first wiring 2, a second wiring 3, and a magnetic layer 4.

[0105] [Effects of one implementation method] In this inductor 1, the ratio (L1 / L2) of the depth L1 of the first recess to the depth L2 of the second recess is 0.67 or more and 1.50 or less. Therefore, warping of the inductor 1 can be suppressed. As a result, the inductor 1 can be reliably mounted on an external substrate (not shown). Furthermore, since warping of the inductor 1 can be suppressed, electronic components (not shown) can be reliably mounted on the inductor 1.

[0106] Therefore, the reduction in the installability of inductor 1 can be suppressed.

[0107] Furthermore, it can suppress the reduction in the operability of inductor 1 caused by the aforementioned warping.

[0108] Therefore, the inductor 1 exhibits excellent dimensional accuracy during machining and excellent positional accuracy during installation. For example, a drilling step for applying alignment marks can be cited as a subsequent step.

[0109] Furthermore, in this inductor 1, as long as the warpage (L3-L4) is less than 200 μm, the warpage described above can be reliably reduced.

[0110] When the tensile storage modulus E' of the second resin sheet 26 at 170°C is lower than the tensile storage modulus E' of the first resin sheet 25 at 170°C, the ratio (L1 / L2) of the depth L1 of the first recess to the depth L2 of the second recess can be set to 1.50 or less.

[0111] <Example of a variation of the implementation method> In the following variations, the reference numerals used to mark the same components and steps as in the above embodiment are omitted in their detailed descriptions. Furthermore, unless otherwise specified, the variations can achieve the same effects as the first embodiment. Moreover, the first embodiment and its variations can be appropriately combined.

[0112] In one embodiment, a plurality of magnetic sheets 30 are generally hot-pressed. Although not shown in the figure, for example, the first sheet 31, the second sheet 32, and the third sheet 33 may be hot-pressed sequentially.

[0113] Although not illustrated, each of the first wiring 2 and the second wiring 3 can be observed in cross-section to have a general polygonal shape (not illustrated). The polygon includes rectangles. Examples of the shapes of the first wiring 2 and the second wiring 3 include spirals, loops, bends, U-shapes, and straight lines.

[0114] The number of wiring can also be 3 or more.

[0115] A release film may be disposed on the first pressing surface 61 of the first mold 73 and / or on the other side of the thickness direction of the flexible sheet 81. Alternatively, a metal plate may be disposed on the first pressing surface 61 of the first mold 73. Examples of materials for the metal plate include stainless steel, duralumin, and brass. [Example]

[0116] The following examples, embodiments, and comparative examples illustrate the present invention in more detail. Furthermore, the present invention is not limited to any particular example, embodiment, or comparative example. Also, the specific values ​​of mixing ratios (including ratios), physical property values, parameters, etc., used below can replace the corresponding upper limits (defined as "below" or "not reached") or lower limits (defined as "above" or "exceeded") of the mixing ratios (including ratios), physical property values, parameters, etc., recorded in the "Embodiments" above.

[0117] Preparation Example 1 (Preparation of adhesives) An adhesive was prepared by mixing 27 parts by weight of epoxy resin (main agent), 27 parts by weight of phenolic resin (curing agent), 1 part by weight of imidazole compound (curing accelerator), 44 parts by weight of acrylic resin (thermoplastic resin), and 1 part by weight of dispersant. Details of the above components are shown in Table 1.

[0118] Example 1 As shown in Figure 5, firstly, a dry laminator (manufactured by Nikkiso Corporation) is prepared as the aforementioned hot pressing device 50. The hot pressing device 50 is equipped with α-gel (manufactured by Taica Corporation) as a flexible, flowable sheet 81.

[0119] Furthermore, the magnetic particles and the adhesive of Preparation Example 1 were mixed and formulated in the volume ratios recorded in Table 2 to produce the first sheet 31, the second sheet 32, and the third sheet 33 (magnetic sheet 30).

[0120] Next, a pressurized laminate 40 is fabricated. Specifically, four third sheets 33 and two first sheets 31 are arranged on a second resin sheet 26 with a thickness of 120 μm, which contains JRR120 (a non-porous release film, trade name: JRR120, material: special polyester, manufactured by Sekisui Chemicals Co., Ltd.). Next, first wiring 2 and second wiring 3 are arranged on the first sheet 31. Each of the first wiring 2 and second wiring 3 has a circular cross-sectional shape and a diameter of 260 μm. Subsequently, two first sheets 31 and four second sheets 32 are arranged on one side of the thickness direction of the first wiring 2 and second wiring 3.

[0121] Next, a first resin sheet 25, 38 μm thick and containing an MRA membrane (polyethylene terephthalate, manufactured by Mitsubishi Chemical Co., Ltd.), is disposed on the second sheet 32. This forms a pressurized laminate 40.

[0122] The pressurized laminate 40 is placed in the first mold 73.

[0123] Subsequently, as shown in Figure 6, the outer frame component 76 is tightly fitted to the first mold 73 to form a sealed space 84. Then, the vacuum pump 78 is driven to depressurize the sealed space 84, forming a depressurized space 85. The difference between the air pressure in the environment where the thermopressurization device 50 is installed and the air pressure in the depressurized space 85 is 101 kPa.

[0124] Subsequently, as shown in Figure 7, the second mold 74 and the inner frame component 75 are brought close to the first mold 73, and the magnetic sheet 30, the first wiring 2, and the second wiring 3 are hot-pressed through the fluid flexible sheet 81, the first resin sheet 25, and the second resin sheet 26. The hot-pressing temperature is 170°C, and the time is 15 minutes. The hot-pressing pressure is 9.0 MPa.

[0125] In this way, an inductor 1 is manufactured having a first wiring 2, a second wiring 3, and a magnetic layer 4.

[0126] Example 2 The inductor 1 was fabricated using the same process as in Example 1. However, as the second resin sheet 26, a 50 μm thick TPX-containing film (non-porous film) and a 1000 μm thick porous fluoropolymer film (FSB735N, manufactured by Maxellkurehae) were used. The non-porous film was brought into contact with the third sheet 33.

[0127] Example 3 The inductor 1 was fabricated using the same process as in Example 1. However, the thickness of the first resin sheet 25 was changed from 38 μm to 75 μm.

[0128] Example 4 The inductor 1 was fabricated using the same process as in Example 1. However, the thickness of the first resin sheet 25 was changed from 38 μm to 150 μm.

[0129] Comparative Example 1 The inductor 1 was fabricated using the same process as in Example 1. However, as the second resin sheet 26, an OT film (flexible film, polybutylene terephthalate, manufactured by Sekisui Chemicals Co., Ltd.) with a thickness of 110 μm and a TPX-containing film with a thickness of 50 μm were used. The TPX-containing film was brought into contact with the third sheet 33. Similarly, as the first resin sheet 25, the aforementioned OT film and the TPX-containing film were used. The TPX-containing film was brought into contact with the second sheet 32.

[0130] Evaluate Regarding Examples 1 to 4 and Comparative Example 1, the following matters were evaluated. The results of the evaluation are shown in Table 3.

[0131] <Observation and Measurement of Warpage> The warpage of inductor 1 shall be measured in the following order.

[0132] A sample 18 was fabricated by machining the inductor 1 to a size of 60 mm in length and 60 mm in width. The sample 18 was placed on the horizontal platform 19 with its second main surface 6 in contact with the surface 20 of the platform 19. The longest length L3 and the shortest length L4 from the surface 20 of the horizontal platform 19 to the first main surface 5 were determined in the central region 21 of the inductor 1, which is 30 mm in length and 30 mm in width. The difference between the longest height L3 and the shortest height L4 (L3-L4) was calculated as the warpage. A shape measuring machine was used for the measurement. The apparatus and conditions are shown below.

[0133] Device: VR-5200, manufactured by Keyence Software: Parsing Applications Pattern: Mean Step Difference

[0134] Meanwhile, the warping state was visually observed. In Example 1 and Comparative Example 1, as shown in FIG3A, there is a bend in the two ends 13 of sample 18 relative to the central region 21 on the other side of the thickness direction. In contrast, in Examples 2 to 4, as shown in FIG3B, there is a bend in the two ends 13 of sample 18 relative to the central region 21 on one side of the thickness direction.

[0135] <Tensive storage modulus E' of the first resin sheet 25 and the second resin sheet 26 at 170°C> Determine the tensile storage modulus E' of the first resin sheet 25 and the second resin sheet 26 at 170°C. Specifically, the tensile storage modulus E' of the sheets at 170°C is measured using the following apparatus under the following conditions.

[0136] Apparatus: UBM Rheogel-E4000 (rheometer) Measurement method: Dynamic viscoelasticity measurement Measurement mode: Temperature dependent Measurement temperature: 0℃ to 300℃ Heating rate: 2℃ / min Chuck: Stretch Distance between clamps: 20 mm Strain: 0.1% Sample size: 4 mm wide Frequency: 1 Hz Measurement atmosphere: Atmosphere (air)

[0137] However, when the sheet has multiple layers, the lowest value among the multiple layers is obtained as the tensile storage modulus E'. Specifically, in the second resin sheet 26 of Example 2, the tensile storage modulus E' of the porous fluoropolymer film is obtained. Regarding the first resin sheet 25 and the second resin sheet 26 of Comparative Example 1, the tensile storage modulus E' of the OT film is obtained.

[0138] [Table 1] Table 1 Epoxy resin Cresol-formaldehyde varnish (main agent) EPICRON N665-EXP-s DIC Company manufactures 27 parts by weight Phenolic resin hardener MEHC-7851SS Meiwa Chemical Co., Ltd. manufactures 27 parts by weight imidazole compounds hardening accelerator 2PHZ-PW Shikoku Chemical Industry Co., Ltd. manufactures 1 part by weight Acrylic resin (thermoplastic resin) Carboxyl-containing acrylate copolymers Teisan Resin SG-70L Manufactured by Nagase Kasei Corporation 44 portions by weight dispersant Phosphate HIPLAAD ED 152 Kusumoto Chemical Manufacturing 1 part by weight

[0139] [Table 2] Table 2 Magnetic sheet thickness (μm) Magnetic particles volume% Magnetic layer Magnetic sheet on one side of the thickness direction relative to the first and second wirings (Stage B) First sheet 75 Carbonyl iron powder *1 61.5 1st magnetic layer (Phase C) First sheet 75 Carbonyl iron powder *1 61.5 Second sheet 85 Fe-Si alloy*2 55 Second magnetic layer (Phase C) Second sheet 85 Fe-Si alloy*2 55 Second sheet 85 Fe-Si alloy*2 55 Second sheet 85 Fe-Si alloy*2 55 The magnetic sheet on the other side of the thickness direction relative to the first and second wirings (stage B) First sheet 75 Carbonyl iron powder *1 61.5 1st magnetic layer (Phase C) First sheet 75 Carbonyl iron powder * 1 61.5 Third sheet 85 Fe-Si alloy*2 55 Second magnetic layer (Phase C) Third sheet 85 Fe-Si alloy*2 55 Third sheet 85 Fe-Si alloy*2 55 Third sheet 85 Fe-Si alloy*2 55 *1 Median particle size 4.1 μm *2 Median particle size 40 μm

[0140] [Table 3] Table 3 Examples and Comparative Examples Example 1 Example 2 Example 3 Example 4 Comparative Example 1 First Resin Sheet type MRA film MRA film MRA film MRA film OT membrane + TPX membrane Thickness (μm) 38 38 75 150 110+50 Tensile storage modulus E' (Pa) at 170℃ 4.1×10⁸ 4.1×10⁸ 4.1×10⁸ 4.1×10⁸ 8.6×10⁵ Second resin sheet type JRR120 TPX membrane + porous fluoropolymer membrane JRR120 JRR120 OT membrane + TPX membrane Thickness (μm) 120 50+1000 120 120 110+50 Tensile storage modulus E' (Pa) at 170℃ 2.5×10⁷ 5.4×10⁵ 2.5×10⁷ 2.5×10⁷ 8.6×10⁵ Compare Stretching storage modulus E' (1st / 2nd) 16.4 759 16.4 16.4 1.0 Thickness (1st / 2nd) 0.3 0.03 0.6 1.25 1.0 depth The depth L1 of the first concave portion 36.3 36.5 29.6 18.5 44.4 The depth L2 of the second concave portion 28.1 44.5 31.1 21.4 22.2 (L1 / L2) 1.29 0.82 0.95 0.85 2.00 Warp L3-L4(μm) 121 92 twenty three 49 226 form Figure 3A Figure 3B Figure 3B Figure 3B Figure 3A

[0141] Furthermore, the above-described invention is provided as an illustrative embodiment of the present invention, but it is merely illustrative and not a limiting interpretation. Variations of the present invention that are readily apparent to those skilled in the art are included within the scope of the following claims. [Industrial Applicability]

[0142] Inductors can be used in power supply circuits of electronic circuits that operate under direct current.

[0143] 1: Inductor 2: Wiring 1 3: Second wiring 4: Magnetic layer 5: 1st main side 6:The second main side 7: First Opposing Part 8: Second opposing part 9: 1st concave part 10: Third opposing part 11: Fourth Opposite Part 12: 2nd concave part 13: Both ends 14: Central Department 15: First magnetic layer 16: Second magnetic layer 17: Third magnetic layer 18: Sample 19: Water Platform 20: Surface 21: Central Region 25: First Resin Sheet 26: Second Resin Sheet 28: Laminated Sheets 29A: Sheet pressing surface 29B: Sheet pressing surface 30: Magnetic sheet 31: First sheet 32: Second sheet 33: Third sheet 40: Pressurized laminate 50: Hot pressing device 60: 2nd concave part 61: First pressure surface 62: Second pressure surface 73: Mold No. 1 74: Mold No. 2 75: Inner frame components 76: Outer frame components 77: Exhaust port 78: Vacuum pump 79: Exhaust pipe 81: Flowable, soft sheet 82: Contact surface 83:Inner side of chamber 84: Enclosed space 85: Stress Relief Space 98: Third pressure surface 99: Inner side L1: Depth L2: Depth L1 / L2: Ratio of the depths of the two recesses L3: Maximum Height L4: Shortest Height L3-L4: Poor (warping)

Claims

1. An inductor having a sheet shape and comprising: a first wiring and a second wiring adjacent to each other in a direction orthogonal to the thickness direction; and a magnetic layer for embedding the first wiring and the second wiring; wherein the magnetic layer has: a first main surface exposed on one side of the thickness direction; and a second main surface exposed on the other side of the thickness direction; wherein the first main surface has a first recess recessed between a first opposing portion and a second opposing portion, the first opposing portion facing the first wiring in the thickness direction, and the second opposing portion facing the second wiring in the thickness direction; wherein the second main surface has a second recess recessed between a third opposing portion and a fourth opposing portion, the third opposing portion facing the first wiring in the thickness direction, and the fourth opposing portion facing the second wiring in the thickness direction; The ratio of the depth of the first recess to the depth of the second recess is 0.67 or more and 1.50 or less.

2. The inductor of claim 1, wherein the warpage determined in the following measurement is less than 200 μm, wherein the measurement refers to: manufacturing a sample by machining the inductor to a size of 60 mm in length and 60 mm in width; placing the sample on the horizontal platform with the second main surface of the sample facing the surface of the horizontal platform; determining the longest and shortest lengths from the surface of the horizontal platform to the first main surface in the central region of the inductor, which is 30 mm in length and 30 mm in width; and determining the difference between the longest and shortest lengths as the warpage.

3. A method for manufacturing an inductor, comprising a step of hot-pressing a pressure-applying laminate, the pressure-applying laminate comprising magnetic particles, a magnetic sheet comprising a thermosetting resin, and a plurality of wires spaced apart from each other in a direction orthogonal to the thickness direction of the magnetic sheet, the pressure-applying laminate further comprising a first resin sheet and a second resin sheet clamping the magnetic sheet and the plurality of wires in the thickness direction, wherein a flowable flexible sheet, the first resin sheet, and the second resin sheet are used in the above step, the second resin sheet, the first resin sheet, and the flowable flexible sheet are sequentially arranged toward one side of the thickness direction, and the tensile storage modulus of the second resin sheet at the hot-pressing temperature is lower than the tensile storage modulus of the first resin sheet at the hot-pressing temperature.

4. The method for manufacturing an inductor as claimed in claim 3, wherein the tensile storage modulus of the second resin sheet at 170°C is lower than the tensile storage modulus of the first resin sheet at 170°C.

5. A method for manufacturing an inductor as claimed in claim 3 or 4, wherein there are multiple magnetic sheets, and in the pressure-applying laminate, the multiple magnetic sheets clamp the multiple wirings in the thickness direction.

6. A method for manufacturing an inductor as claimed in claim 3 or 4, wherein, in the above steps, the same degree of stress deformation is generated in the laminated sheet comprising the fluid flexible sheet and the first resin sheet, and the second resin sheet, respectively, by the reaction force from the plurality of wirings and the magnetic sheet.

7. The method of manufacturing an inductor as claimed in claim 5, wherein in the above steps, the same degree of stress deformation is generated in the laminated sheet comprising the fluid flexible sheet and the first resin sheet and the second resin sheet by the reaction force from the plurality of wirings and the magnetic sheet.

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