Inductor and manufacturing method thereof

Abstract

This inductor (1) has the form of a sheet. The inductor (1) comprises a first wiring (2) and second wiring (3), and a magnetic layer (4) in which the first wiring (2) and second wiring (3) are embedded. 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 of depth L1 of the first recess (9) with respect to depth L2 of the second recess (12) (L1 / L2) is 0.67 to 1.50.

Description

[Technical Field]

[0001] The present invention relates to an inductor and a method for manufacturing the same. [Background technology]

[0002] A sheet-shaped inductor is known that includes two laterally adjacent wirings and a magnetic layer that embeds them (see, for example, Patent Document 1 below). In the inductor described in Patent Document 1, one surface in the thickness direction of the magnetic layer has first opposing portions that face the two wirings and a first recess that is recessed toward the other side between the two opposing portions. The other surface in the thickness direction of the magnetic layer has second opposing portions that face the two wirings and a second recess that is recessed toward one side between the two second opposing portions. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-150059 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, the first recess is significantly deeper than the second recess. As a result, due to the difference in depth, the inductor warps so that both lateral ends of the inductor move to one side in the thickness direction relative to the lateral center. This makes it difficult to mount the inductor on an external substrate and also makes it difficult to mount electronic elements on the inductor. In other words, this poses a problem of reduced mountability of the inductor.

[0005] Furthermore, the warping described above causes a problem of reduced ease of handling of the inductor.

[0006] The present invention provides an inductor that can suppress deterioration in mountability and handling, and a method for manufacturing the inductor. [Means for solving the problem]

[0007] The present invention (1) includes an inductor having a sheet shape, comprising: a first wiring and a second wiring adjacent to each other and spaced apart in a direction perpendicular to a thickness direction; and a magnetic layer in which the first wiring and the second wiring are embedded; the magnetic layer has a first main surface exposed to one side in the thickness direction and a second main surface exposed to the other side in the thickness direction; the first main surface has a first recess recessed from a first opposing portion opposing the first wiring in the thickness direction and a second opposing portion opposing the second wiring in the thickness direction, the first main surface having a second recess recessed from a third opposing portion opposing the first wiring in the thickness direction and a fourth opposing portion opposing the second wiring in the thickness direction, the ratio (L1 / L2) of a depth L1 of the first recess to a depth L2 of the second recess being 0.67 or more and 1.50 or less.

[0008] 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, so warping of the inductor is suppressed. As a result, the inductor can be reliably mounted on an external substrate. Furthermore, because warping of the inductor is suppressed, electronic elements can be reliably mounted on the inductor. Therefore, deterioration of the inductor's mountability is suppressed.

[0009] Furthermore, it is possible to prevent the deterioration of the handling ability of the inductor due to the warping.

[0010] Therefore, this inductor has excellent dimensional accuracy in post-processing and positional accuracy during mounting.

[0011] The present invention (2) includes the inductor according to (1), in which the warpage required by the following measurement is 200 μm or less.

[0012] The inductor is shaped to a size of 60 mm long and 60 mm wide to prepare a sample. The sample is placed on the horizontal table so that the second main surface of the sample faces the surface of the horizontal table. In an area of ​​30 mm long and 30 mm wide at the center of the inductor, the longest length L3 and the shortest length L4 from the surface of the horizontal table to the second main surface are determined. Length L3 and the above Short length The difference between L3 and L4 (L3-L4) is calculated as the warpage.

[0013] This inductor has a maximum Length L3 and the highest Short length The difference between L3 and L4 (L3-L4) is 200 μm or less, so warpage can be reliably reduced.

[0014] The present invention (3) includes a method for manufacturing an inductor, which includes a step of hot pressing a press laminate including a magnetic sheet containing magnetic particles and a thermosetting resin, and a plurality of wirings spaced apart from each other in a direction perpendicular to the thickness direction of the magnetic sheet, wherein the press laminate further includes a first resin sheet and a second resin sheet that sandwich the magnetic sheet and the plurality of wirings in the thickness direction, and the step uses a flowable flexible sheet, the first resin sheet, and the second resin sheet, and the second resin sheet, the first resin sheet, and the flowable flexible sheet are arranged in order toward one side in the thickness direction, and the tensile storage modulus E' of the second resin sheet at the heat pressing temperature is lower than the tensile storage modulus E' of the first resin sheet at the heat pressing temperature.

[0015] The present invention (4) includes the method for producing an inductor according to 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.

[0016] The present invention (5) includes a method for manufacturing an inductor according to claim 3 or claim 4, wherein there are multiple magnetic sheets, and in the press laminate, the multiple magnetic sheets sandwich the multiple wirings in the thickness direction.

[0017] The present invention (6) includes a method for manufacturing an inductor described in any one of claims 3 to 5, wherein in the process, a reaction force from the plurality of wirings and the magnetic sheet causes stress deformation of the same degree in the laminated sheet consisting of the fluid flexible sheet and the first resin sheet, and in the second resin sheet. [Effects of the Invention]

[0018] The inductor manufactured by the manufacturing method of the present invention can suppress deterioration in mountability and handling. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a cross-sectional view of an embodiment of an inductor of the present invention. [Figure 2] FIG. 2 shows the orientation of magnetic particles in the magnetic layer of the inductor shown in FIG. [Figure 3] 3A and 3B are schematic diagrams illustrating a method for measuring warpage of an inductor. Fig. 3A shows warpage in which both ends in the first direction are located on the other side of the center in the thickness direction. Fig. 3B shows warpage in which both ends in the first direction are located on one side of the center in the thickness direction. [Figure 4] FIG. 4 is a schematic diagram illustrating a method for manufacturing an inductor. [Figure 5] FIG. 5 shows the process of setting the press laminate in a heat press device. [Figure 6] FIG. 6 shows the step of forming a reduced pressure space, following FIG. [Figure 7] FIG. 7 shows the step of hot pressing the magnetic sheet, following FIG. DETAILED DESCRIPTION OF THE INVENTION

[0020] <One embodiment> An embodiment of the inductor of the present invention will be described with reference to FIGS.

[0021] <Inductor 1> The inductor 1 has a sheet shape. The inductor 1 extends in a first direction perpendicular to the thickness direction. The thickness direction is the up-down direction in FIGS. 1 and 2. The first direction is the left-right (horizontal) direction in FIGS. 1 and 2. The inductor 1 includes a first wiring 2, a second wiring 3, and a magnetic layer 4.

[0022] <First wiring 2 and second wiring 3> The first wiring 2 and the second wiring 3 are adjacent to each other with a gap in the first direction. The first wiring 2 and the second wiring 3 are spaced apart from each other in an adjacent direction perpendicular to the longitudinal direction and the thickness direction. The longitudinal direction is the paper thickness direction in FIGS. 1 and 2. Of the first wiring 2 and the second wiring 3, the first wiring 2 is arranged on one side in the first direction. The second wiring 3 is arranged on the other side in the first direction. Each of the first wiring 2 and the second wiring 3 has, for example, a generally circular shape in cross section. The configuration and dimensions of the first wiring 2 and the second wiring 3 are described, for example, in JP 2020-150057 A.

[0023] <Magnetic layer 4> The magnetic layer 4 has the same outer shape as the inductor 1. Specifically, the magnetic layer 4 has a sheet shape extending in the first direction. The magnetic layer 4 has the first wiring 2 and the second wiring 3 buried therein. The magnetic layer 4 has a first major surface 5 and a second major surface 6 .

[0024] The first main surface 5 is exposed on one side in the thickness direction. The first main surface 5 is one surface of the inductor 1 in the thickness direction. When projected in the first direction, the first main surface 5 is disposed on one side in 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.

[0025] The first opposing portion 7 faces, with a gap therebetween, one side in the thickness direction of the first wiring 2. Specifically, the first opposing portion 7 curves along one surface in the thickness direction of the first wiring 2. The first opposing portion 7 is a first protrusion.

[0026] The second opposing portion 8 faces one side of the second wiring 3 in the thickness direction at a distance. Specifically, the second opposing portion 8 curves along one surface of the second wiring 3 in the thickness direction. The second opposing portion 8 is a second protrusion. The second opposing portion 8 is spaced apart from the first opposing portion 7 on the other side in the first direction.

[0027] 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 the other edge in the first direction of the first opposing portion 7 and one edge in the first direction of the second opposing portion 8 toward the other side in the thickness direction. The depth L1 of the first recess 9 is not limited as long as the ratio (L1 / L2) described below 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 or the second opposing portion 8 that is disposed furthest to one side in the thickness direction and the portion of the first recess 9 that is disposed furthest to the other side in the thickness direction.

[0028] The second main surface 6 is exposed on the other side in the thickness direction. The second main surface 6 is the other side in the thickness direction of the inductor 1. When projected in 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.

[0029] The third opposing portion 10 faces the other side of the first wiring 2 in the thickness direction with a gap therebetween. Specifically, the third opposing portion 10 curves along the other surface of the first wiring 2 in the thickness direction. The third opposing portion 10 is a third protrusion. The third opposing portion 10 is disposed on the opposite side of the first wiring 2 from the first opposing portion 7 in the thickness direction.

[0030] The fourth opposing portion 11 faces the other side of the second wiring 3 in the thickness direction at a distance. Specifically, the fourth opposing portion 11 curves along the other surface of the second wiring 3 in the thickness direction. The fourth opposing portion 11 is a fourth protrusion. The fourth opposing portion 11 is disposed on the opposite side of the second opposing portion 8 with respect to the second wiring 3 in the thickness direction. The fourth opposing portion 11 is spaced apart from the other side of the third opposing portion 10 in the first direction.

[0031] 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 the other edge in the first direction of the third opposing portion 10 and one edge in the first direction of the fourth opposing portion 11 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 a 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 or the fourth opposing portion 11 that is disposed furthest to the other side in the thickness direction and the portion of the second recess 12 that is disposed furthest to the one side in the thickness direction.

[0032] 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 exceeds 1.50, the warpage of the inductor 1 becomes large.

[0033] 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. If the ratio is equal to or greater than the lower limit, warpage in which both end portions 13 in the first direction are positioned to one side in the thickness direction relative to the center portion 14 (see FIG. 3B) can be reduced.

[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 1.30 or less, more preferably 1.20 or less, and even more preferably 1.10 or less. If the ratio is equal to or less than the upper limit, it is possible to reduce warpage in which both end portions 13 in the first direction are positioned on the other side in the thickness direction relative to the center portion (see FIG. 3A).

[0035] 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, more preferably 10 μm or less, particularly preferably 5 μm or less, and most preferably 2 μm or less. The difference is |L1-L2|. If the difference is equal to or less than the above-mentioned upper limit, warping of the inductor 1 can be suppressed.

[0036] The materials and properties of the magnetic layer 4 are described in, for example, JP 2020-150057 A. Specifically, the magnetic layer 4 contains magnetic particles and a resin. Examples of the magnetic particles include carbonyl iron powder and Fe—Si alloys. Specific shapes of the magnetic particles include spherical shapes and substantially flat (plate) shapes. A preferred example of the magnetic particles is carbonyl iron powder having a spherical shape. The resin includes, for example, a thermosetting resin.

[0037] The magnetic layer 4 may be a single layer or multiple layers. When the magnetic layer 4 is multiple layers, the magnetic layer 4 preferably contains spherical magnetic particles.

[0038] When the magnetic layer 4 is a multi-layer structure, the magnetic layer 4 includes, 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 in this order toward one side in the thickness direction.

[0039] The first magnetic layer 15 contacts the outer peripheral surfaces of the first wiring 2 and the second wiring 3 and embeds them. As shown in Figure 2, the first magnetic layer 15 preferably contains spherical magnetic particles. This provides the inductor 1 with excellent DC bias characteristics. The first magnetic layer 15 has one surface and the other surface spaced apart from each other in the thickness direction.

[0040] The second magnetic layer 16 is disposed on one surface in the thickness direction of the first magnetic layer 15. The second magnetic layer 16 includes the first main surface 5 described above. The second magnetic layer 16 preferably includes flat magnetic particles. The flat magnetic particles can be oriented in the curved shapes of the first opposing portion 7 and the second opposing portion 8. This can improve the inductance of the inductor 1.

[0041] The third magnetic layer 17 is disposed on the other surface in the thickness direction of the first magnetic layer 15. The third magnetic layer 17 includes the second main surface 6 described above. The third magnetic layer 17 preferably includes flat magnetic particles. The flat magnetic particles can be oriented in the curved shapes of the third opposing portion 10 and the fourth opposing portion 11. This can improve the inductance of the inductor 1.

[0042] <Physical properties of inductor 1> The warpage of the inductor 1 required in the following measurement 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. If the warpage of the inductor 1 is equal to or less than the above-mentioned upper limit, the warpage of the inductor 1 can be reliably reduced.

[0043] <Measurement of warpage of inductor 1> Inductor 1 is machined to have a size of 60 mm in length and 60 mm in width to produce sample 18. As shown in Figures 3A and 3B, sample 18 is placed on horizontal stand 19 so that second main surface 6 of sample 18 faces surface 20 of horizontal stand 19. In central area 21 of inductor 1, which is 30 mm in length and 30 mm in width, the longest length L3 and shortest length L4 from surface 20 of horizontal stand 19 to first main surface 5 are determined. Maximum lengthL3 and Minimum length The difference between L3 and L4 (L3-L4) is calculated as the warpage.

[0044] 3A depicts a curve in which both end portions 13 of sample 18 are disposed on the other side of central area 21 in the thickness direction, i.e., a curve having a substantially inverted U shape. In this case, central area 21 is spaced apart vertically from surface 20 of horizontal base 19. In this case, L3 is the distance from surface 20 of horizontal base 19 to center 14 of first main surface 5 of central area 21. L4 is the distance from surface 20 of horizontal base 19 to the end of first main surface 5 of central area 21.

[0045] In contrast, FIG. 3B depicts a curve in which both end portions 13 of sample 18 are disposed on the other side of central area 21 in the thickness direction, i.e., a substantially U-shaped curve. In this case, central area 21 includes a portion that contacts surface 20. In this case, L3 is the distance from surface 20 of horizontal base 19 to the end of first main surface 5 of central area 21. L4 is the distance from surface 20 of horizontal base 19 to central portion 14 of first main surface 5 of central area 21. More specifically, L4 is the thickness T of central portion 14, since the above-mentioned portion contacts surface 20.

[0046] There are no limitations on the method for manufacturing the inductor 1. For example, as shown in Fig. 4, there is a method for manufacturing the inductor 1 from a first wiring 2, a second wiring 3, and a magnetic sheet 30. This manufacturing method also uses a first resin sheet 25, a second resin sheet 26, and a fluid flexible sheet 81. Specifically, the first resin sheet 25, the second resin sheet 26, and the fluid flexible sheet 81 are used in a heat pressing process described below.

[0047] There may be one or more magnetic sheets 30. The magnetic sheets 30 are arranged on one side and / or the other side of the first wiring 2 and the second wiring 3 in the thickness direction.

[0048] When there are multiple magnetic sheets 30, the magnetic sheets 30 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 for producing the first magnetic layer 15 (see FIGS. 1 and 2). The second sheet 32 ​​is a magnetic sheet for producing the second magnetic layer 16 (see FIGS. 1 and 2). The third sheet 33 is a magnetic sheet for producing the third magnetic layer 17 (see FIGS. 1 and 2). The first sheet 31, the second sheet 32, and the third sheet 33 may each be singular or plural. The magnetic sheet 30 is made of the magnetic composition described in JP 2020-150057 A. Note that the thermosetting resin in the magnetic composition constituting the magnetic sheet 30 is in a B-stage.

[0049] When there are multiple first sheets 31, the second sheet 32, one first sheet 31, the first wiring 2 and second wiring 3, another first sheet 31, and the third sheet 33 are laminated in this order toward the downstream side in the pressing direction. The pressing direction is the up-and-down direction in Figures 5 to 7.

[0050] The first resin sheet 25 and the second resin sheet 26 are buffer sheets and release sheets used in heat pressing, and are not included in the inductor 1. Furthermore, the first resin sheet 25, the second resin sheet 26, and the fluid flexible sheet 81 each have heat resistance and conformability.

[0051] The first resin sheet 25 is used by being disposed on one side in the thickness direction of 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 with respect to one of the first sheet 31 and the second sheet 32. The tensile storage modulus E' of the first resin sheet 25 at 170°C is, for example, 1×10 5 Pa or more, preferably 2 x 10 5 Pa or more, more preferably 1×10 8 Pa or more, particularly preferably 2×10 8 Pa or more, and for example, 1 × 10 10 Pa or less, preferably 5 x 10 9The tensile storage modulus E' of the first resin sheet 25 is, for example, a catalog value, or can be actually measured. The temperature "170°C" at which the tensile storage modulus E' is obtained is within the temperature range of the heat press.

[0052] The second resin sheet 26 is disposed on the opposite side of the first resin sheet 25 with respect to the first wiring 2 and the second wiring 3. In other words, the second resin sheet 26 is disposed on the other side in the thickness direction with respect 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 with respect to the other first sheets 31 and third sheets 33.

[0053] The second resin sheet 26 is, for example, softer than the first resin sheet 25. If the second resin sheet 26 has the same hardness (or tensile storage modulus E', described later) as the first resin sheet 25, the depth L1 of the first recesses 9 on the first main surface 5, which contact the first resin sheet 25 flexibly supported by the flowable flexible sheet 81 described below, may be significantly greater than the depth L2 of the second recesses 12. However, as described above, if the second resin sheet 26 is softer than the first resin sheet 25, the second resin sheet 26 can flexibly contact the second main surface 6, just like the first resin sheet 25, which is flexibly contacted by the flowable flexible sheet 81. Therefore, the depth L2 of the second recesses 12 can be set to be approximately the same as the depth L1 of the first recesses 9.

[0054] The tensile storage modulus E' of the second resin sheet 26 at 170°C is, for example, 1×10 5 Pa or more, preferably 1 x 10 6 Pa or more, and for example, 1 × 10 9 Pa or less, preferably 1×10 8 The tensile storage modulus E' of the second resin sheet 26 is, for example, a catalog value, or can be actually 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.

[0055] 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.

[0056] The ratio of the tensile storage modulus E' at 170°C of the first resin sheet 25 to the tensile storage modulus E' at 170°C of the second resin sheet 26 is, for example, more than 1, preferably 2 or more, more preferably 3 or more, even more preferably 4 or more, particularly preferably 5 or more, and most preferably 7 or more. The above ratio is, for example, 10,000 or less, preferably 1,000 or less, more preferably 100 or less, and even more preferably 20 or less. When the above ratio is equal to or greater than the above lower limit or equal to or less than the above upper limit, an inductor 1 with reduced warpage can be manufactured.

[0057] If each of the first resin sheet 25 and the second resin sheet 26 is made up of multiple layers, the lowest value among the multiple layers is taken as the tensile storage modulus E'. The layer having the lowest tensile storage modulus E' conforms to the magnetic layer 4.

[0058] The thicknesses of the first resin sheet 25 and the second resin sheet 26 are not limited, as long as they satisfy the following ratio, for example. 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 is, for example, 2 or less, preferably 1 or less, more preferably less than 1, and even more preferably 0.8 or less. If the above ratio is equal to or greater than the above lower limit or equal to or less than the above upper limit, the warpage of the inductor 1 can be further reduced. When the first resin sheet 25 is multi-layered, the thickness of the first resin sheet 25 is the total thickness of the multi-layered parts. When the second resin sheet 26 is multi-layered, the thickness of the second resin sheet 26 is the total thickness of the multi-layered parts.

[0059] The material of the first resin sheet 25 and the second resin sheet 26 is resin. There are no limitations on the resin. Examples of resin include polyester, polyolefin, and fluororesin. Examples of polyester include polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). Polyester includes special polyester. Examples of polyolefin include polyethylene, polypropylene, and polymethylpentene (TPX). The first resin sheet 25 and the second resin sheet 26 are each non-porous and / or porous.

[0060] The first resin sheet 25 is a single layer or multiple layers, and the second resin sheet 26 is a single layer or multiple layers.

[0061] The fluid flexible sheet 81 is disposed on one side in the thickness direction of the first resin sheet 25. The fluid flexible sheet 81 is disposed on the opposite side of the first resin sheet 25 to the one first sheet 31 and the second sheet 32.

[0062] The material of the fluid flexible sheet 81 is not limited as long as it is a material that can exhibit fluidity and flexibility during heat pressing. Examples of the material of the fluid flexible sheet 81 include gel or soft elastomer. The material of the fluid flexible sheet 81 may be a commercially available product, such as the αGEL series (manufactured by Taica Corporation) and the RIKEN ELASTOMER series (manufactured by RIKEN TECHNOS CORPORATION). The thickness of the fluid flexible sheet 81 is not limited. The lower limit of the thickness of the fluid flexible sheet 81 is, for example, 1 mm, preferably 2 mm, and the upper limit of the thickness of the fluid flexible sheet 81 is, for example, 1,000 mm, preferably 100 mm.

[0063] 4, the laminate sheet 28 made of the flowable flexible sheet 81 and the first resin sheet 25 has the same softness (hardness) as, for example, the second resin sheet 26. Specifically, the tensile storage modulus E' at 170°C of the laminate sheet 28 made of the flowable flexible sheet 81 and the first resin sheet 25 is approximate to, for example, the tensile storage modulus E' at 170°C of the second resin sheet 26.

[0064] Next, as an example of a method for manufacturing the inductor 1, a manufacturing method using a heat press device 50 will be described with reference to FIGS.

[0065] In the method for manufacturing this inductor 1, the magnetic sheet 30, the first wiring 2, the second wiring 3, the fluid flexible sheet 81, the first resin sheet 25, and the second resin sheet 26 are heat-pressed together using a heat press device 50.

[0066] The heat press device 50 is an isotropic press device that can isotropically heat press (isotropically press) the magnetic sheet 30, the first wiring 2, and the second wiring 3 (see FIG. 5 ), for example. The heat press device 50 includes a first die 73, a second die 74, an inner frame member 75, an outer frame member 76, and a fluid flexible sheet 81.

[0067] In this example, the heat press device 50 is configured so that the second die 74, inner frame member 75, and outer frame member 76 can approach and press (closely contact) the first die 73. The first die 73 is immovable in the pressing direction of the heat press device 50.

[0068] The first die 73 has a generally plate-like shape. The first die 73 has a first press surface 61 that faces a second die 74, which will be described next. The first press surface 61 extends in a direction (plane direction) perpendicular to the pressing direction. The first press surface 61 is flat. Furthermore, the first die 73 includes a heater (not shown).

[0069] The second die 74 is spaced apart from the first die 73 in the pressing direction. The second die 74 is movable in the pressing direction relative to the first die 73. The second die 74 has a generally plate-like shape that is smaller than the first die 73. Specifically, the second die 74 is contained within the first die 73 when projected in the pressing direction. More specifically, the second die 74 overlaps with the center of the first die 73 in the surface direction when projected in the pressing direction. The second die 74 has a second pressing surface 62 that faces the center of the first pressing surface 61 of the first die 73 in the surface direction. The second pressing surface 62 extends in the surface direction. The second press surface 62 is parallel to the first press surface 61. The second die 74 also includes a heater (not shown).

[0070] The inner frame member 75 surrounds the second die 74. Although not shown in detail, the inner frame member 75 surrounds the entire periphery of the second die 74. The inner frame member 75 is spaced apart from the peripheral edge of the first die 73 in the pressing direction. In other words, the inner frame member 75 is disposed opposite the peripheral edge of the first die 73 at a distance in the pressing direction. The inner frame member 75 integrally includes a third press surface 98 that faces the peripheral edge of the first press surface 61, and an inner side surface 99 that faces inward. The inner frame member 75 is movable in the pressing direction relative to the first die 73. On the other hand, the inner frame member 75 is movable in conjunction with the second die 74 in the pressing direction.

[0071] The outer frame member 76 surrounds the inner frame member 75. Although not shown in detail, the outer frame member 76 surrounds the entire periphery of the inner frame member 75. The outer frame member 76 is spaced apart from the peripheral edge of the first die 73 in the pressing direction. In other words, the outer frame member 76 is disposed opposite the peripheral edge of the first die 73 at a distance in the pressing direction. The outer frame member 76 integrally has a contact surface 82 that faces the peripheral edge of the first press surface 61, and a chamber inner side surface 83 that faces inward. The outer frame member 76 is movable in the pressing direction relative to both the first die 73 and the inner frame member 75.

[0072] The outer frame member 76 also has an exhaust port 77. The upstream end of the exhaust port 77 in the exhaust direction faces the chamber inner side surface 83. The exhaust port 77 is connected to a vacuum pump 78 via an exhaust line 79. Note that the exhaust line 79 is normally closed.

[0073] The fluid flexible sheet 81 is not provided in the press laminate 40 described below, but is provided in advance in the hot press device 50. The fluid flexible sheet 81 is arranged on the second press surface 62 of the second die 74. The fluid flexible sheet 81 is also arranged on the inner surface 99 of the inner frame member 75. More specifically, the fluid flexible sheet 81 is in contact with the entire surface of the second press surface 62 and the downstream portion of the inner surface 99 in the press direction. The inner frame member 75 is movable in the press direction relative to the fluid flexible sheet 81.

[0074] The heat press device 50 is described in detail in, for example, Japanese Patent Application Laid-Open No. 2004-296746. A commercially available product can be used as the heat press device 50. For example, the Dry Laminator series manufactured by Nikkiso Co., Ltd. can be used as the heat press device 50.

[0075] 5, in this method, first, a press laminate 40 is prepared and set in a heat press device 50. The press 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 this press laminate 40, the second resin sheet 26, a third sheet 33, another first sheet 31, the first wiring 2 and the second wiring 3, one first sheet 31, the second sheet 32, and the first resin sheet 25 are arranged in this order toward one side in the thickness direction.

[0076] To prepare the press laminate 40, first, the third sheet 33 and the other first sheet 31 are placed in this order on one side of the second resin sheet 26 in the thickness direction.

[0077] Next, the first wiring 2 and the second wiring 3 are disposed on one side of another first sheet 31 in the thickness direction.

[0078] Thereafter, one first sheet 31 and one second sheet 32 ​​are placed in relation to the first wiring 2 and the second wiring 3 in that order.

[0079] Next, the first resin sheet 25 is placed on one side of the second sheet 32 ​​in the thickness direction.

[0080] In this way, a laminate 40 for pressing is prepared.

[0081] Next, the prepared press laminate 40 is set in the heat press device 50. Specifically, the second resin sheet 26 is placed on the first press surface 61 of the first die 73. Furthermore, the first resin sheet 25 in the press laminate 40 faces the fluid flexible sheet 81.

[0082] Thereafter, as shown by the arrow in FIG. 5 and in FIG. 6, the outer frame member 76 is brought into contact with the first die 73 to form a reduced pressure space 85.

[0083] Specifically, the outer frame member 76 is pressed against the peripheral edge of the first press surface 61 of the first die 73. This causes the contact surface 82 of the outer frame member 76 and the peripheral edge of the first press surface 61 of the first die 73 to come into intimate contact (close contact) (preferably press) with each other, thereby forming an enclosed space 84.

[0084] The sealed space 84 is defined by the chamber inner side surface 83 of the outer frame member 76 , the third press surface 98 of the inner frame member 75 , the flowable flexible sheet 81 , and the first press surface 61 of the first die 73 .

[0085] The pressure of the outer frame member 76 against the first mold 73 is set to a level that ensures airtightness (tightness to the outside) of the reduced pressure space 85 described below by the close contact of the contact surface 82 and the first press surface 61, and specifically, is 0.1 MPa or more and 20 MPa or less.

[0086] As a result, a sealed space 84 is formed between the first die 73, the outer frame member 76, and the second die 74. The sealed space 84 is shielded from the outside. However, an exhaust line 79 can communicate with the sealed space 84.

[0087] On the other hand, the first resin sheet 25 and the flowable flexible sheet 81 are still spaced apart in the pressing direction.

[0088] Subsequently, the sealed space 84 is decompressed to form a decompressed space 85 .

[0089] Specifically, the vacuum pump 78 is driven, and then the exhaust line 79 is opened. This reduces the pressure in the sealed space 84 that communicates with the exhaust port 77. This turns the sealed space 84 into a reduced-pressure space 85.

[0090] The upper limit of the difference between the atmospheric pressure in the environment where the heat press device 50 is installed and the atmospheric pressure in the reduced pressure space 85 (and the exhaust line 79) is, for example, 1,000,000 Pa, and the lower limit of the difference is, for example, 1 Pa.

[0091] Then, as shown by the arrows in Figure 6 and Figure 7, the second mold 74 and inner frame member 75 are brought close to the first mold 73, and the magnetic sheet 30, the first wiring 2, and the second wiring 3 are heat-pressed via the fluid flexible sheet 81, the first resin sheet 25, and the second resin sheet 26.

[0092] The second die 74 is moved in the pressing direction. Then, the flowable flexible sheet 81 approaches the first resin sheet 25 in accordance with the movement of the second die 74 and the inner frame member 75. The inner frame member 75 moves in conjunction with the second die 74.

[0093] As a result, the fluid flexible sheet 81 flexibly contacts the entire upstream side of the first resin sheet 25 in the pressing direction, except for the peripheral edge. At this time, because the fluid flexible sheet 81 has fluidity and flexibility, it adheres closely to the first resin sheet 25, conforming to the shapes of the first wiring 2 and the second wiring 3. At this time, because the inner frame member 75 moves in conjunction with the second die 74, part of the inner surface 99 of the inner frame member 75 contacts the peripheral side of the fluid flexible sheet 81. The third pressing surface 98 of the inner frame member 75 contacts the peripheral edge of the first pressing surface 61 of the first die 73.

[0094] Furthermore, the second die 74 is heat-pressed toward the first die 73 .

[0095] The lower limit of the heat press 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°C, preferably 110°C, more preferably 130°C, and the upper limit is, for example, 200°C, preferably 185°C, more preferably 175°C. 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.

[0096] As a result, the magnetic sheet 30, the first wiring 2, and the second wiring 3 are pressed with equal pressure from both sides in the thickness direction and the surface direction of the magnetic sheet 30. In other words, the magnetic sheet 30, the first wiring 2, and the second wiring 3 are isotropically pressed.

[0097] Then, the magnetic sheet 30 flows so as to bury the first wiring 2 and the second wiring 3.

[0098] Furthermore, the peripheral side surface of the magnetic sheet 30 is pressed inward from the side (outside) by the fluid flexible sheet 81. Therefore, the peripheral side surface of the magnetic sheet 30 is prevented from flowing outward.

[0099] In the above-described heat pressing, first resin sheet 25 is harder than second resin sheet 26, but is supported by flexible and fluid flexible sheet 81, and as a result, it flexibly supports (contacts) second main surface 6 of inductor 1. On the other hand, second resin sheet 26 is softer than first resin sheet 25, and can support (contact) first recess 9 of inductor 1 with the same degree of softness as second resin sheet 26. Therefore, inductor 1 having first recess 9 and second recess 12 with the above-described ratio is manufactured.

[0100] Specifically, if the tensile storage modulus E' at 170°C of the laminated sheet 28 made of the flowable flexible sheet 81 and the first resin sheet 25 is similar to the tensile storage modulus E' at 170°C of the second resin sheet 26, the reaction forces from the first wiring 2, the second wiring 3, and the magnetic sheet 30 during the heat press described above cause the same degree of stress deformation in the laminated sheet 28 made of the flowable flexible sheet 81 and the first resin sheet 25 and the second resin sheet 26. This allows the two sheet press surfaces 29A and 29B to conform to the shapes of the first wiring 2, the second wiring 3, and the magnetic sheet 30 that are being pressed. Therefore, the ratio (L1 / L2) of the depth L1 of one recess to the depth L2 of the second recess can be set within a predetermined range (specifically, 0.67 or more and 1.50 or less). The sheet press surface 29A during the heat press is the other surface of the first resin sheet 25 in the thickness direction. The sheet press surface 29B in the heat press is one surface of the second resin sheet 26 in the thickness direction.

[0101] The flow of the magnetic sheet 30 described above is caused by the flow of the B-stage thermosetting resin due to heating by the heaters of the first die 73 and the second die 74, and the flow of the thermoplastic resin that is blended in as needed.

[0102] Further heating by the heater causes the thermosetting resin to enter C-stage, that is, a magnetic layer 4 containing magnetic particles and a cured body (C-stage body) of the thermosetting resin is formed.

[0103] In this way, the inductor 1 including the first wiring 2, the second wiring 3, and the magnetic layer 4 is manufactured.

[0104] [Effects of one embodiment] 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 is suppressed. As a result, the inductor 1 can be reliably mounted on an external substrate (not shown). Furthermore, because warping of the inductor 1 is suppressed, an electronic element (not shown) can be reliably mounted on the inductor 1.

[0105] Therefore, the mounting ease of the inductor 1 is prevented from being reduced.

[0106] Furthermore, it is possible to prevent the inductor 1 from becoming difficult to handle due to the warping.

[0107] Therefore, this inductor 1 has excellent dimensional accuracy in post-processing and positional accuracy during mounting. Post-processing can include, for example, a drilling process for providing alignment marks.

[0108] Furthermore, in this inductor 1, if the warpage (L3-L4) is 200 μm or less, the warpage described above can be reliably reduced.

[0109] 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 one recess to the depth L2 of the second recess can be set to 1.50 or less.

[0110] <Modification of one embodiment> In the following modifications, the same components and steps as those in the above-described embodiment are denoted by the same reference numerals, and detailed descriptions thereof will be omitted. Furthermore, the modifications can achieve the same effects as those in the above-described embodiment, unless otherwise specified. Furthermore, the embodiment and its modifications can be combined as appropriate.

[0111] In one embodiment, multiple magnetic sheets 30 are heat-pressed together, but although not shown, for example, the first sheet 31, the second sheet 32, and the third sheet 33 can also be heat-pressed in sequence.

[0112] Although not shown, each of the first wiring 2 and the second wiring 3 may have a generally polygonal cross-sectional shape. Polygonal shapes include rectangular shapes. Examples of the shapes of the first wiring 2 and the second wiring 3 include spiral, loop, meander, U-shaped, and linear shapes.

[0113] The number of wires may be three or more.

[0114] A release film can be placed on the first pressing surface 61 of the first die 73 and / or the other surface in the thickness direction of the flowable flexible sheet 81. A metal plate can also be placed on the first pressing surface 61 of the first die 73. Examples of materials for the metal plate include stainless steel, duralumin, and brass. [Example]

[0115] The present invention will be described in more detail below with reference to preparation examples, examples, and comparative examples. It should be noted that the present invention is not limited to the preparation examples, examples, and comparative examples. The specific numerical values ​​of the blending ratios (content ratios), physical property values, parameters, etc. used in the following description can be replaced with the upper limit (a numerical value defined as "equal to or less than") or lower limit (a numerical value defined as "equal to or more than" or "exceeding") of the corresponding blending ratios (content ratios), physical property values, parameters, etc. described in the "Description of the Invention" above.

[0116] Preparation Example 1 (Preparation of binder) A binder was prepared by mixing 27 parts by mass of epoxy resin (main component), 27 parts by mass of phenolic resin (curing agent), 1 part by mass of imidazole compound (curing accelerator), 44 parts by mass of acrylic resin (thermoplastic resin), and 1 part by mass of dispersant. Details of each of the above components are shown in Table 1.

[0117] Example 1 5, first, a dry laminator (manufactured by Nikkiso Co., Ltd.) was prepared as the above-mentioned heat press device 50. The heat press device 50 was equipped with αGEL (manufactured by Taica Corporation) as the flowable flexible sheet 81.

[0118] In addition, the magnetic particles and the binder of Preparation Example 1 were compounded and mixed to obtain the volume ratios shown in Table 2 to prepare a first sheet 31, a second sheet 32, and a third sheet 33 (magnetic sheet 30).

[0119] Next, a press laminate 40 was produced. Specifically, four third sheets 33 and two first sheets 31 were placed on a second resin sheet 26 made of JRR120 (non-porous release film, product number: JRR120, material: special polyester, manufactured by Sekisui Chemical Co., Ltd.) with a thickness of 120 μm. Next, a first wiring 2 and a second wiring 3 were placed on the first sheet 31. Each of the first wiring 2 and the second wiring 3 had a circular cross section and a diameter of 260 μm. After that, two more first sheets 31 and four second sheets 32 were placed on one side of the first wiring 2 and the second wiring 3 in the thickness direction.

[0120] Next, a first resin sheet 25 made of a 38 μm thick MRA film (polyethylene terephthalate, manufactured by Mitsubishi Chemical Corporation) was placed on the second sheet 32. In this way, a laminate 40 for press use was produced.

[0121] The produced press laminate 40 was placed in the first die 73 .

[0122] 6, the outer frame member 76 was brought into close contact with the first die 73 to form a sealed space 84. Subsequently, the vacuum pump 78 was driven to reduce the pressure in the sealed space 84, thereby forming a reduced pressure space 85. The difference obtained by subtracting the pressure in the reduced pressure space 85 from the pressure in the environment in which the heat press device 50 was installed was 101 kPa.

[0123] 7, the second die 74 and inner frame member 75 were brought close to the first die 73, and the magnetic sheet 30, the first wiring 2, and the second wiring 3 were heat-pressed via the fluid flexible sheet 81, the first resin sheet 25, and the second resin sheet 26. The heat-pressing temperature was 170°C, and the heat-pressing time was 15 minutes. The heat-pressing pressure was 9.0 MPa.

[0124] In this way, an inductor 1 including the first wiring 2, the second wiring 3, and the magnetic layer 4 was manufactured.

[0125] Example 2 An inductor 1 was fabricated in the same manner as in Example 1. However, a 50 μm-thick film (non-porous film) made of TPX and a 1000 μm-thick porous fluororesin film (FSB735N, manufactured by Maxell Kureha Co., Ltd.) were used as second resin sheet 26. The non-porous film was brought into contact with third sheet 33.

[0126] Example 3 An inductor 1 was fabricated in the same manner as in Example 1. However, the thickness of the first resin sheet 25 was changed from 38 μm to 75 μm.

[0127] Example 4 An inductor 1 was fabricated in the same manner as in Example 1. However, the thickness of the first resin sheet 25 was changed from 38 μm to 150 μm.

[0128] Comparative Example 1 An inductor 1 was fabricated using the same process as in Example 1. However, as the second resin sheet 26, a 110 μm-thick OT film (flexible film, polybutylene terephthalate, manufactured by Sekisui Chemical Co., Ltd.) and a 50 μm-thick film made of TPX were used. The film made of TPX was brought into contact with the third sheet 33. Furthermore, as the first resin sheet 25, the above-mentioned OT film and a film made of TPX were used. The film made of TPX was brought into contact with the second sheet 32.

[0129] evaluation The following items were evaluated for Examples 1 to 4 and Comparative Example 1. The evaluation results are shown in Table 3.

[0130] <Observation and measurement of warpage> The warpage of the inductor 1 was measured according to the following procedure.

[0131] The inductor 1 was cut to a size of 60 mm in length and 60 mm in width to produce a sample 18. The sample 18 was placed on a horizontal stand 19 so that the second main surface 6 of the sample 18 was in contact with the surface 20 of the horizontal stand 19. In a central area 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 horizontal stand 19 to the first main surface 5 were determined. Length L3 and the highest Short length The difference between L3 and L4 (L3 - L4) was calculated as the warpage. A shape measuring instrument was used for the measurement. The equipment and conditions are as follows:

[0132] Equipment: VR-5200, manufactured by Keyence Corporation Software: Analysis application Mode: Average step height

[0133] Additionally, the state of warpage was visually observed. In Example 1 and Comparative Example 1, as shown in Fig. 3A, both end portions 13 of sample 18 were curved such that they were positioned on the other side in the thickness direction relative to central area 21. In contrast, in Examples 2 to 4, as shown in Fig. 3B, both end portions 13 of sample 18 were curved such that they were positioned on one side in the thickness direction relative to central area 21.

[0134] <Tensile storage modulus E′ of first resin sheet 25 and second resin sheet 26 at 170° C.> The tensile storage modulus E' at 170° C. was determined for the first resin sheet 25 and the second resin sheet 26. Specifically, the tensile storage modulus E' at 170° C. of the sheets was measured using the following device under the following conditions.

[0135] Apparatus: UBM Rheogel-E4000 (rheometer) Measurement method: Dynamic viscoelasticity measurement Measurement mode: Temperature dependence Measurement temperature: 0℃ to 300℃ Heating rate: 2℃ / min Chuck: Tensile Chuck distance: 20mm Distortion: 0.1% Sample size: 4mm wide Frequency: 1Hz Measurement atmosphere: atmosphere (air)

[0136] However, when the sheet had multiple layers, the lowest value among the layers was taken as the tensile storage modulus E'. Specifically, for the second resin sheet 26 of Example 2, the tensile storage modulus E' of a porous fluororesin film was taken. For each of the first resin sheet 25 and the second resin sheet 26 of Comparative Example 1, the tensile storage modulus E' of an OT film was taken.

[0137] [Table 1]

[0138] [Table 2]

[0139] [Table 3]

[0140] The above invention is provided as an exemplary embodiment of the present invention, but it is merely an example and should not be interpreted as being limiting. Modifications of the present invention that are obvious to those skilled in the art are included in the scope of the following claims. [Industrial Applicability]

[0141] Inductors are used in power supply circuits for electronic circuits that operate on direct current. [Explanation of symbols]

[0142] 1 inductor 2 1st wiring 3 2nd wiring 4 magnetic layer 5 First main surface 6 Second main surface 7 First opposing part 8 Second opposing part 9 First recess 10 Third opposing part 11 Fourth opposing part 12 Second recess 18 Samples 19 Horizontal platform 20 surface 21 Central Area 25 First resin sheet 26 Second resin sheet 28 Laminated Sheet 30 Magnetic Sheet 31 Sheet 1 32 2nd Sheet 33 Third Sheet 40 Press laminate 60 Second recess 81 Fluid flexible sheet L1 / L2 ratio (ratio of the depths of the two recesses) L3-L4 difference (warpage)

Claims

1. An inductor having a sheet shape, a first wiring and a second wiring adjacent to each other at an interval in a direction perpendicular to the thickness direction; a magnetic layer in which the first wiring and the second wiring are embedded, The magnetic layer is a first main surface exposed on one side in the thickness direction; a second main surface exposed on the other side in the thickness direction, the first main surface has a first opposing portion opposing the first wiring in the thickness direction and a first recessed portion recessed from a second opposing portion opposing the second wiring in the thickness direction, between the first opposing portion and the second opposing portion; the second main surface has a third opposing portion opposing the first wiring in the thickness direction and a fourth opposing portion opposing the second wiring in the thickness direction, the second main surface having a second recess recessed therefrom between the third opposing portion and the fourth opposing portion; An inductor, wherein a ratio (L1 / L2) of a depth L1 of the first recess to a depth L2 of the second recess is 0.67 or more and 1.50 or less.

2. 2. The inductor according to claim 1, wherein the warpage measured as follows is 200 μm or less. The inductor is shaped to a size of 60 mm long and 60 mm wide to prepare a sample. The sample is placed on the horizontal table so that the second main surface of the sample faces the surface of the horizontal table. In a central area of ​​the inductor measuring 30 mm long and 30 mm wide, the longest length L3 and the shortest length L4 from the surface of the horizontal table to the first main surface are determined. The difference between the longest length L3 and the shortest length L4 (L3 - L4) is determined as the warpage.

3. A method for manufacturing an inductor, comprising a step of hot-pressing a press laminate including a magnetic sheet containing magnetic particles and a thermosetting resin, and a plurality of wirings spaced apart from each other in a direction perpendicular to a thickness direction of the magnetic sheet, the press laminate further includes a first resin sheet and a second resin sheet sandwiching the magnetic sheet and the plurality of wirings in a thickness direction; In the step, a flowable flexible sheet, the first resin sheet, and the second resin sheet are used, In the step, the second resin sheet, the first resin sheet, and the flowable flexible sheet are arranged in this order toward one side in the thickness direction, The method for manufacturing an inductor, wherein the second resin sheet has a lower tensile storage modulus E' at the heat press temperature than the first resin sheet at the heat press temperature.

4. 4. The method for manufacturing an inductor according to claim 3, wherein the second resin sheet has a tensile storage modulus E' at 170°C lower than the tensile storage modulus E' at 170°C of the first resin sheet.

5. The magnetic sheet is a plurality of sheets, 5. The method for manufacturing an inductor according to claim 3, wherein in the press laminate, the plurality of magnetic sheets sandwich the plurality of wirings in the thickness direction.

6. A method for manufacturing an inductor described in any one of claims 3 to 5, wherein in the process, due to the reaction force from the multiple wirings and the magnetic sheet, the same degree of stress deformation occurs in the laminate sheet consisting of the fluid flexible sheet and the first resin sheet, and in the second resin sheet.

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