Manufacturing method of multilayer inductor

Abstract

To provide a manufacturing method for a multilayer inductor, which can reduce the number of layers in the manufacture of the multilayer inductor.SOLUTION: A manufacturing method for a multilayer inductor includes preparing a plurality of first sheets A each having a conductor portion and a magnetic portion formed on the lower side of a magnetic sheet, and a first via portion penetrating the magnetic sheet above the conductor portion, stacking the plurality of first sheets A, and forming a first coil layer including a first coil to which the conductor portion is electrically connected via the first via portion.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a stacked inductor.

Background Art

[0002] In recent years, due to the high functionality of devices, the DC-DC converters of voltage conversion circuits have been increasing in large current and high efficiency, and the rated current of the power inductors used in these devices has also been increasing.

[0003] Patent Document 1 showing an example of the above inductor discloses a passive component including an insulating substrate portion; an internal conductor built in the substrate portion and including a coil conductor and a lead-out conductor drawn from the coil conductor; and an external electrode electrically connected to the internal conductor. Patent Document 1 also discloses a method for manufacturing a stacked passive component by laminating green sheets.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the conventional method for manufacturing a stacked passive component, each pattern layer (referring to a plurality of layers or a single layer formed by laminating a plurality of the same patterns) is formed by printing and laminating a plurality of green sheets, so the number of laminations is relatively large, and the manufacturing cost increases, which has been a problem. For example, when manufacturing a stacked inductor having the structure shown in the cross-sectional view of FIG. 3 described later, in the conventional manufacturing method, each pattern layer n1 to n17 (especially pattern layers n3 to n17) is formed by laminating a plurality of each, so the number of laminations is relatively large and the manufacturing cost increases.

[0006] The main object of the present disclosure is to provide a method for manufacturing a laminated inductor capable of reducing the number of laminations in the manufacture of the laminated inductor.

Means for Solving the Problems

[0007] The present disclosure prepares a plurality of first sheets A each having a conductor portion and a magnetic portion formed on the lower side of a magnetic sheet and a first via portion penetrating the magnetic sheet on the upper side of the conductor portion, and relates to a method for manufacturing a laminated inductor, which laminates the plurality of first sheets A to form a first coil layer including a first coil in which the conductor portions are electrically connected via the first via portions. Regarding.

Effects of the Invention

[0008] According to the present disclosure, the number of laminations can be reduced in the manufacture of a laminated inductor. Specifically, since a specific sheet is used, the method for manufacturing a laminated inductor of the present disclosure can reduce the number of laminations as compared with the conventional method for manufacturing a laminated inductor in which a large number of green sheets are laminated for each pattern layer.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0010] Hereinafter, a method for manufacturing a stacked inductor according to the present disclosure will be described. Note that the stacked inductor manufactured by the manufacturing method of the present disclosure is not limited to the following configuration, and may be appropriately changed without departing from the gist of the present disclosure. In addition, a combination of a plurality of the following individually preferable configurations is also within the scope of the present disclosure.

[0011] In this specification, terms indicating the relationship between elements (e.g., "parallel", "orthogonal", "perpendicular", etc.) and terms indicating the shape of elements do not mean only a strictly literal aspect, but also mean a substantially equivalent range, for example, a range including a difference of about several percent. In this specification, the direction in which sheets are stacked during manufacturing is defined as the "stacking direction" (e.g., direction T in Fig. 1).

[0012] As used in this specification, "plan view" refers to the state (top view or bottom view) when an object is viewed from above or below along the thickness direction based on the stacking direction. In particular, the state when an object is viewed from below (or the bottom side) along the thickness direction based on the stacking direction may be referred to as "bottom view" (bottom view or bottom surface view). Also, "cross-sectional view" refers to the cross-sectional state (cross-sectional view) when an object is viewed from a direction substantially perpendicular to the stacking direction T (for example, direction L or W in FIG. 1). The "vertical direction" and "horizontal direction" directly or indirectly used in this specification correspond to the vertical direction and horizontal direction in the figure, respectively. Unless otherwise specified, the same reference numerals or symbols indicate the same members, parts, or the same meaning content. In a preferred embodiment, it can be understood that the vertically downward direction (i.e., the direction in which gravity acts) corresponds to the "downward direction", and the opposite direction corresponds to the "upward direction". In particular, in the method for manufacturing a bottom electrode type laminated inductor having electrodes on the bottom surface, the "lower side" and "upper side" respectively refer to the "lower side" and "upper side" in a cross-sectional view or an exploded view thereof when the laminated inductor is placed with the bottom surface having electrodes on the lower side and the upper surface opposite to the bottom surface on the upper side and left stationary.

[0013] The drawings shown below are schematic diagrams, and their dimensions, scales of aspect ratios, etc. may be different from those of actual products.

[0014] An example embodiment of the method for manufacturing a laminated inductor according to the present disclosure will be described with reference to FIGS. 1 to 6. Note that the shapes and arrangements of the laminated inductor and each component are not limited to the illustrated examples.

[0015] FIG. 1 shows a perspective view schematically showing a laminated inductor manufactured by the manufacturing method according to the present disclosure. As shown in FIG. 1, the laminated inductor 1 generally includes a coil 3 in which a coil conductor is wound inside a base body (magnetic body) 2 containing iron powder, a via portion 4 that electrically connects the coil conductors (conductor portions) of the coil 3 to each other, a through portion 5 that is electrically connected to the coil conductor (conductor portion) of the coil 3 and extends in the direction of the bottom surface of the base body, and an external electrode portion 6 that is disposed on the bottom surface side of the base body and is electrically connected to the through portion 5. The "via portion" is a via hole portion filled with a conductive material and is a member that can be simply referred to as a "via hole portion" or a "via conductor portion". The "through portion" is a through hole portion filled with a conductive material and is a member that can be simply referred to as a "through hole portion" or a "through conductor portion".

[0016] The coil 3 includes, but is not limited to, two coils (i.e., a first coil and a second coil indicated by reference numerals 31 and 32, respectively) in FIG. 1, and the number of coils may be one or three or more. The number of turns of the first coil and the second coil is 2.5 each, but is not particularly limited. In the present specification, the "via portion" is used in the concept of a connection path for electrically connecting coils to each other, and the "through portion" is used in the concept of a connection path for electrically connecting a coil to an external electrode portion. Therefore, even a member referred to as a "through portion" may be referred to as a "via portion" if it has a function of electrically connecting coils to each other due to its arrangement as its function. Conversely, even a member referred to as a "via portion" may be referred to as a "through portion" if it has a function of electrically connecting a coil to an external electrode portion due to its arrangement as its function.

[0017] The base body 2 has, for example, a rectangular parallelepiped shape or a substantially rectangular parallelepiped shape having six faces. The base body 2 may have rounded vertices and edges. A vertex is a portion where three faces of the base body 2 intersect, and an edge is a portion where two faces of the base body 2 intersect.

[0018] In FIG. 1, the length direction, width direction, and height direction in the stacked inductor 1 and the base body 2 are shown as the L direction, W direction, and T direction, respectively. The length direction L, width direction W, and height direction T are orthogonal to each other. The mounting surface of the stacked inductor 1 is, for example, a surface (LW surface) parallel to the length direction L and the width direction W.

[0019] The base body 2 shown in FIG. 1 has a first main surface B1 and a second main surface B2 facing each other in the height direction T, a first end surface B5 and a second end surface B6 facing each other in the length direction L orthogonal to the height direction T, and a first side surface B3 and a second side surface B4 facing each other in the width direction W orthogonal to the length direction L and the height direction T. In the example shown in FIG. 1, the first main surface B1 of the base body 2 corresponds to the mounting surface (bottom surface) of the base body 2.

[0020] The base body 2 includes a coil 3 in which a coil conductor is wound inside a magnetic body, a via portion 4 that electrically connects the coil conductors of the coil 3 to each other, a through portion 5 that is electrically connected to the coil conductor of the coil 3 and extends in the bottom surface direction of the base body 2, and an external electrode portion 50 that is disposed on the bottom surface side of the base body and is electrically connected to the through portion 5. A plurality of coils (for example, a first coil 31 and a second coil 32) may be included in the magnetic body in the stacking direction (for example, the height direction T).

[0021] FIG. 2 is an exploded perspective view for explaining the stacking structure of the stacked inductor 1 in FIG. 1. FIG. 3 is a cross-sectional view schematically showing the A-A cross-section of the stacked inductor in FIG. 1. As shown in FIGS. 2 and 3, the stacked inductor 1 of the present disclosure is composed of pattern layers n1 to n17. In FIGS. 1 and 2, the through portion 5 is depicted as a simple columnar shape, but in the actual cross-section, as shown in FIG. 3, in each pattern layer, the via portion, through portion, and external electrode portion may have different shapes in a plan view. In FIG. 3, the blank area inside the base body 2 indicates a magnetic portion 20 made of a magnetic sheet 200 unless otherwise specified, and the hatched area indicates a conductor portion such as a coil, through portion, and via portion. In particular, in FIG. 3, the conductor portion 30 disposed in the stacking groups G3, G4, and G6 to G8 described later and the via portion 4 disposed directly above it may correspond to the through portion 5 of the stacking group in FIG. 2.

[0022] In the present disclosure, the multilayer inductor 1 is manufactured by laminating multilayer groups G1 to G12.

[0023] In the method for manufacturing a multilayer inductor according to the present disclosure, lamination is performed using a non-penetrating sheet (hereinafter sometimes referred to as the "first sheet"), and preferably lamination is performed using the first sheet and a penetrating sheet (hereinafter sometimes referred to as the "second sheet") from the viewpoint of further reducing the number of laminated layers.

[0024] FIG. 4 is a flowchart showing steps for explaining a method for manufacturing a first sheet (including first sheet A, first sheet B, and first sheet C) used in the method for manufacturing a multilayer inductor of the present disclosure. The first sheet is a non-penetrating sheet manufactured without penetrating a base material during manufacturing, and includes a first sheet A denoted by the symbol "IA" in step (7a) of FIG. 4, a first sheet B denoted by the symbol "IB" in step (7b), and a first sheet C denoted by the symbol "IC" in step (7c) according to the thickness of the magnetic portion 20 and the presence or absence of a remaining pad portion 95 described later.

[0025] (First sheet A) The first sheet A is represented by the symbol "IA" in, for example, FIGS. 2, 3, 4, and 6, and has a linear conductor portion 30 and a magnetic portion 20 formed on the lower side of the magnetic sheet 200, and a via portion 4 (the via portion of the first sheet A may be referred to as the first via portion) that penetrates the magnetic sheet 200 above the conductor portion 30. The via portion 4 is usually disposed above the end of the linear conductor portion 30 formed continuously in plan view. On one surface (particularly the upper surface) of the first sheet A, the surface (exposed surface) of the via portion 4 is usually flush with the surface (exposed surface) of the magnetic sheet 200. On the other surface (particularly the lower surface) of the first sheet A, the surface (exposed surface) of the conductor portion 30 is usually flush with the surface (exposed surface) of the magnetic portion 20. In this specification, being flush means that there is no step between two adjacent surfaces. In the present disclosure, since the first sheet A corresponding to two conventional sheets is used, the number of stacked layers during manufacturing can be reduced. Further, as will be described later, the first sheet A can be manufactured without penetrating the substrate by forming the magnetic sheet 200 as a thinner magnetic layer. For this reason, the first sheet A can easily adjust the thickness of the element body (particularly each pattern layer constituting the element body). Furthermore, since the first sheet A can be manufactured using only one substrate as shown in the manufacturing method described later for each sheet, it is excellent in manufacturing cost. Furthermore, by using the first sheet A, with a limited element body size, the via portion can be formed thinner and the conductor portion can be formed thicker, so that the characteristics of the inductor can be improved. Note that the via portion 4 of the first sheet A may be a through hole or both a via portion and a through hole depending on the arrangement of the first sheet A. For example, in the first sheet A shown in FIG. 3, the conductor portion 30 and the via portion 4 disposed directly above it may be integrally referred to as a via portion or a through hole. When referred to as a through hole, the conductor portion 30 may have a non-linear shape (for example, an island shape) in plan view and may have a circular shape or a polygonal shape (for example, a square shape, etc.).

[0026] As shown in FIG. 4, the first sheet A is manufactured by the following method. First, a magnetic sheet 200 is formed on a substrate 90 using a sheet forming method such as the doctor blade method as a magnetic layer (step (1)). The thickness K1 of the magnetic sheet is not particularly limited, and for example, it may be 10 μm or more and 100 μm or less, particularly 10 μm or more and 20 μm or less. The method for forming the magnetic layer is not particularly limited, and for example, after printing by a printing method such as a coating printing method or a sheet printing method, the magnetic layer may be formed by drying.

[0027] In the printing method, a magnetic paste is used. As an example of a method for producing the magnetic paste, iron powder with a D50 (cumulative 50% particle size based on volume) of 2 μm or more and 20 μm or less is prepared. The "iron powder" is not strictly limited to being in a powdery form, and also includes those in which the powder particles are bonded by heat treatment (firing) described later. The iron powder may contain Fe and / or Si. More specifically, it may be Fe particles or Fe alloy particles. The Fe alloy may be an Fe-Si alloy, an Fe-Si-Cr alloy, an Fe-Si-Al alloy, an Fe-Si-B-P-Cu-C alloy, and / or an Fe-Si-B-Nb-Cu alloy, etc. Also, the iron powder may contain impurities such as Cr, Mn, Cu, Ni, P, S, and / or Co that are not intentionally added during production. Since the iron powder is contained in the magnetic paste, the iron powder may contain elements (e.g., Cr, Al, Li, Zn) that are more easily oxidized than Fe added during the production of the magnetic paste. The iron powder is made to contain cellulose or polyvinyl butyral (PVB) as a binder, a mixture of terpineol and butyl diglycol acetate (BCA) as a solvent, etc., and kneaded to produce the magnetic paste. When using an Fe-Si alloy as the iron powder, the Si content is preferably 2.0 at% or more and 8.0 at% or less. When using an Fe-Si-Cr alloy as the iron powder, the Si content is preferably 2.0 at% or more and 8.0 at% or less. Also, when using an Fe-Si-Cr alloy as the iron powder, the Cr content is preferably 0.2 at% or more and 6.0 at% or less. An insulating film may be provided on the surface of the iron powder. The insulating film is preferably a film containing a metal oxide, and more preferably an oxide of Si. As a method for forming the insulating film, the sol-gel method is preferred. As an example of forming the insulating film by the sol-gel method, a sol-gel coating agent containing Si alkoxide and an organic chain-containing silane coupling agent are mixed to form a mixed solution. After this mixed solution is adhered to the surface of the metal magnetic powder, heat treatment is applied to cause dehydration bonding. Then, the insulating film can be formed by drying at a predetermined temperature.

[0028] The material of the base material 90 is not particularly limited, and for example, it may be composed of a polymer such as polyester (e.g., polyethylene terephthalate). The thickness of the base material 90 is not particularly limited as long as the magnetic sheet (magnetic layer) 200 can be carried and peeled off from the magnetic layer.

[0029] Next, a portion corresponding to the via portion described later in the magnetic sheet 200 is selectively removed from the magnetic sheet side by laser irradiation (step (2)). At this time, the base material 90 is not penetrated. Since a laser is used for forming the via portion in this way, the via portion has a tapered shape in a cross-sectional view. Further, after inversion in a subsequent step, in order to form the conductor portion and the magnetic portion, the via portion has a tapered shape with a smaller upper side in a cross-sectional view. The "tapered shape with a smaller upper side" means a shape in which the width of the upper side of the tapered shape is smaller than the width of the lower side in a cross-sectional view. For example, when the via portion has a circular shape in a plan view, it has a frustum of a cone shape as a whole (particularly, a frustum of a cone shape in which the area of the upper surface is smaller than the area of the bottom surface).

[0030] After the selective removal, a positive metal mask 92 is used (step (3)), and a conductive paste is printed by a screen printing method to form a via portion in the removed portion 91 (step (4)).

[0031] A conductor paste is used in the screen printing method for forming the via portion. The conductor paste is prepared by adding a binder and a solvent to a conductive material and kneading them.

[0032] The conductive material can be any conductive material that can be used to form coils, via portions, and / or through portions in the field of laminated inductors. For example, Ag, Au, Cu, Ni, Pd, Sn, or alloys of two or more of them can be used. The binder and solvent contained in the conductor paste are not particularly limited and may be selected from within the same range as the binder and solvent contained in the magnetic paste, respectively. In the above-described step (3), in view of misalignment of the metal mask, etc., since it is difficult for the via portion 4 to be formed only in the region of the removal portion 91 strictly, in this step (4), usually, a metal mask with an opening larger than the via portion 4 in plan view is used. Therefore, a flange-shaped pad portion 95 is formed around the via portion 4. The "flange shape" is a shape that protrudes around the via portion and is characterized in cross-sectional view and plan view (especially cross-sectional view). For example, in cross-sectional view, the "flange shape" is a shape in which the pad portion 95 extends in a direction perpendicular to the lamination direction T more than the via portion 4. Also, for example, in plan view, the "flange shape" is a shape in which the pad portion 95 is arranged around the via portion 4. Note that in plan view, the pad portion 95 does not necessarily have to be arranged continuously around the entire circumference of the via portion 4 and may be formed intermittently (or discontinuously) in the circumferential direction of the via portion.

[0033] After forming the via portion, a conductor portion 30 is formed on the via portion 4 using a positive metal mask 92, and a magnetic portion 20 is formed in a region other than the conductor portion 30 on the surface of the magnetic sheet 200 using a negative metal mask (not shown in FIG. 92) having a pattern opposite to that of the positive metal mask (step (5a 1 ))). By appropriately repeating the printing of the formation of the conductor portion and the magnetic portion by screen printing a suitable number of times, the conductor portion and the magnetic portion can be thickened (step (5a 2 ) and (5a 3In the method for manufacturing the first sheet A, in order to form the conductor portion 30 on the via portion 4, the pad portion 95 formed in step (4) becomes a part of the conductor portion 30. The conductive paste for forming the conductor portion used in this step may be selected from within a similar range as the conductor paste for forming the via portion used in step (4). The magnetic paste for forming the magnetic portion used in this step may be selected from within a similar range as the magnetic paste used in step (1).

[0034] After forming the conductor portion and the magnetic portion, it is inverted (step (6a)), and by peeling the base material 90, the first sheet A can be obtained.

[0035] In the first sheet A, the diameter D1 of the via portion 4 (first via portion) can be made smaller than the width D2 of the conductor portion 30 (see Fig. 6(A)). While reducing the diameter of the via portion is effective for miniaturizing the laminated inductor, reducing the diameter of the via portion deteriorates the electrical characteristics during lamination and reduces the reliability of the connection. On the other hand, since the first sheet A is effective for reducing the number of laminations, the reliability of the electrical connection during lamination can be enhanced, so the diameter D1 of the via portion 4 can be easily made smaller than the width D2 of the conductor portion 30.

[0036] The diameter D1 of the via portion 4 is the average value of the minimum diameters of each of any 10 via portions in a cross-sectional view parallel to the width direction or the length direction of the base body and passing through the center of the via portion. The diameter D1 is not particularly limited, and for example, it may be 50 μm or more and 200 μm or less, particularly 100 μm or more and 150 μm or less. Note that when the member does not have a circular shape in plan view, the diameter may be the width. The width D2 of the conductor portion 30 is the average value of the minimum widths of each of any 10 conductor portions 30 in a cross-sectional view parallel to the width direction or the length direction of the base body and passing through the center of the via portion. The width D2 is not particularly limited, and for example, it may be 100 μm or more and 330 μm or less, particularly 130 μm or more and 180 μm or less.

[0037] In the first sheet A, the thickness T1 of the via portion 4 (first via portion) is thinner than the thickness T2 of the conductor portion 30 (see FIG. 6(A)). Thereby, since the magnetic sheet 200 can be formed as a thinner magnetic layer, the first sheet A becomes more useful for adjusting the thickness of the base body (particularly each pattern layer constituting the base body).

[0038] In the first sheet A, the thickness T1 of the via portion 4 is the average value of the minimum thicknesses of each of the 10 arbitrary via portions in a cross-sectional view. The thickness T1 is not particularly limited and may be a value within the same range as the thickness K1 of the magnetic sheet in the first sheet A described above.

[0039] In the first sheet A, the thickness T2 of the conductor portion 30 is the average value of the minimum thicknesses of each of the 10 arbitrary conductor portions 30 in a cross-sectional view. The thickness T2 is not particularly limited and may be, for example, 20 μm or more and 120 μm or less, particularly 40 μm or more and 90 μm or less.

[0040] (First sheet B) The first sheet B is represented by the symbol "IB" in, for example, FIGS. 2, 3, 4, and 6, and has via portions 4 (the via portions of the first sheet B may be referred to as second via portions) that penetrate the magnetic sheet 200, and has a magnetic portion 20 in a region other than the via portions 4 on the lower surface of the magnetic sheet 200. The via portions 4 of the first sheet B may be through portions depending on the arrangement of the first sheet B, or may be both via portions and through portions. Specifically, the first sheet B may have one or more via portions 4 or one or more through portions, or may have one or more via portions 4 and one or more through portions. On one surface (particularly the upper surface) of the first sheet B, the surface (exposed surface) of the via portion 4 is usually flush with the surface (exposed surface) of the magnetic sheet 200. On the other surface (particularly the lower surface) of the first sheet B, the surface (exposed surface) of the via portion 4 is usually flush with the surface (exposed surface) of the magnetic portion 20. In the present disclosure, since the first sheet B is manufactured without penetrating the base material as described later, the magnetic sheet 200 can be formed as a thinner magnetic layer. Therefore, the first sheet B is also useful for adjusting the thickness of the element body (particularly each pattern layer constituting the element body), similar to the first sheet A. Furthermore, since the first sheet B can be manufactured using only one base material as shown in the manufacturing method described later for each sheet, the first sheet B is also excellent in manufacturing cost, similar to the first sheet B.

[0041] As shown in FIG. 4, the first sheet B is manufactured by the following method. Steps (1) to (4) are performed in the same manner as in steps (1) to (4) in the manufacturing method of the first sheet A to form via portions 4 in the removed portion 91 of the magnetic sheet 200. In the manufacturing method of the first sheet B, since a laser is used to form the via portions (particularly the second via portions) in this way, the via portions have a tapered shape in cross-sectional view. Furthermore, since they are inverted in subsequent steps, the via portions have a "tapered shape with a smaller upper side" in cross-sectional view. For example, when the via portions have a circular shape in plan view, the via portions have a frustoconical shape as a whole (particularly a frustoconical shape in which the area of the upper surface is smaller than the area of the bottom surface).

[0042] After forming the via portions, a negative metal mask is used to form the magnetic portion 20 in regions other than the via portions 4 (step (5b)). The magnetic paste for forming the magnetic portion used in this step may be selected from within a similar range as the magnetic paste used in step (1). In the manufacturing method of the first sheet B, since the magnetic portion 20 is formed in a region other than the via portions 4 without intentionally forming the conductor portion 30 on the via portions 4 formed in step (4), the pad portion 95 remains as a flange-shaped conductor portion. Specifically, the pad portion 95 is not intentionally formed, but is formed by itself around (for example, the outer peripheral portion) of the via portion 4 during the formation of the via portion (particularly the second via portion) 4, and is composed of the same conductive material as the via portion. For this reason, the pad portion 95 may also be referred to as a "flange-shaped conductor portion". Therefore, as shown in step (7b) described later, the first sheet B has, below the magnetic sheet 200, a flange-shaped conductor portion (that is, the pad portion 95) formed around (for example, the outer peripheral portion) of the via portion (particularly the second via portion) 4 and a magnetic portion 20 formed further around the flange-shaped conductor portion. More specifically, the first sheet B shown in step (7b) described later has, in a bottom view, the second via portion 4, a flange-shaped conductor portion (that is, the pad portion 95) formed around (for example, the outer peripheral portion) of the second via portion, and a magnetic portion 20 formed further around the flange-shaped conductor portion. In the first sheet B, particularly, the magnetic portion 20 is formed, more specifically, in a region other than the via portion (particularly the second via portion) 4 and the flange-shaped conductor portion (that is, the pad portion 95) on the lower surface of the magnetic sheet 200.

[0043] After forming the conductor portion and the magnetic portion, it is inverted (step (6b)), and by peeling the base material 90, the first sheet B can be obtained (step (7b)).

[0044] In the first sheet B, the diameter D3 of the via portion 4 (second via portion) is usually smaller than the width D40 of the flange-shaped conductor portion (pad portion 95) on the lower surface of the magnetic sheet 200 (see FIG. 6(B)). As described above, this is one of the features of the first sheet B based on the fact that the via portion (particularly the second via portion) 4 has a tapered shape with a smaller upper side in a cross-sectional view and the pad portion 95 remains. The width D40 of the flange-shaped conductor portion (pad portion 95) on the lower surface of the magnetic sheet 200 is the total width (or maximum width) of the via portion 4 (second via portion) including the flange-shaped conductor portion (pad portion 95).

[0045] In the first sheet B, the diameter D3 (see FIG. 6(B)) of the via portion 4 (second via portion) is not particularly limited and may be, for example, a value within the same range as the diameter D1 of the via portion 4 (first via portion) in the first sheet A. The diameter D3 of the via portion 4 is the average value of the minimum diameters of each of any 10 via portions in a cross-sectional view. Here too, when the member does not have a circular shape in a plan view, the diameter may be the width.

[0046] In the first sheet B, the thickness T3 (see FIG. 6(B)) of the via portion 4 (second via portion) is not particularly limited and may be, for example, a value within the same range as the thickness T1 of the via portion 4 (first via portion) in the first sheet A. The thickness T3 of the via portion 4 is the average value of the minimum thicknesses of each of any 10 via portions in a cross-sectional view.

[0047] In the first sheet B, the width D4 (see FIG. 6(B)) of the pad portion 95 is usually 5 μm or more and 30 μm or less, and may particularly be 10 μm or more and 15 μm or less. The width D4 of the pad portion 95 is the average value of the minimum widths of each of any 10 pad portions in a cross-sectional view.

[0048] In the first sheet B, the width D40 of the region of the via portion 4 (second via portion) on the lower surface of the magnetic sheet 200 is the average value of the widths of any 10 via portion regions in a cross-sectional view parallel to the width direction or the length direction of the base body and passing through the center of the via portion. The width D40 is not particularly limited, and for example, it may be 60 μm or more and 250 μm or less, particularly 150 μm or more and 200 μm or less.

[0049] In the first sheet B, the thickness T4 of the pad portion 95 (see FIG. 6(B)) is not particularly limited, and for example, as an example, it may be 1 μm or more and 50 μm or less, particularly 5 μm or more and 20 μm or less.

[0050] (First sheet C) The first sheet C is represented by the symbol "IC" in FIGS. 2, 3, 4, and 6, for example, and has an island-shaped external electrode portion 6 and a magnetic portion 20 formed on the lower side of the magnetic sheet 200, and a via portion 4 (the via portion of the first sheet C may be referred to as the third via portion) penetrating the magnetic sheet 200 above the external electrode portion 6. On one surface (particularly the upper surface) of the first sheet C, the surface (exposed surface) of the via portion 4 is usually flush with the surface (exposed surface) of the magnetic sheet 200. On the other surface (particularly the lower surface) of the first sheet C, the surface (exposed surface) of the external electrode portion 6 is usually flush with the surface (exposed surface) of the magnetic portion 20. In the present disclosure, by using the first sheet C corresponding to two sheets in the conventional method, the number of stacked layers during manufacturing can be reduced in the same manner as when using the first sheet A. Further, by using the first sheet C, the external electrode portion can be formed thinly with a limited size of the base body, so that the characteristics of the inductor can be improved. Furthermore, since the first sheet C can be manufactured using only one base material as shown in the manufacturing method described later for each sheet, the first sheet C is also excellent in manufacturing cost like the first sheet A.

[0051] The first sheet C is manufactured by the following method as shown in FIG. 4. In the same manner as steps (1) to (4) in the manufacturing method of the first sheet A, steps (1) to (4) are performed to form via portion 4 in the removed portion 91 of the magnetic sheet 200. In the manufacturing method of the first sheet C, since a laser is used to form via portions (particularly the third via portion) in this way, the via portion has a tapered shape in cross-sectional view. Further, since it is inverted in subsequent steps, the via portion has a "tapered shape with a smaller upper side" in cross-sectional view. For example, when the via portion has a circular shape in plan view, the via portion has a frustum of a cone shape as a whole (particularly a frustum of a cone shape in which the area of the upper surface is smaller than the area of the bottom surface).

[0052] After forming the via portion, a positive metal mask 92 and a conductive paste are used to form external electrode portion 6 on the via portion 4, and a negative metal mask (not shown) having a pattern opposite to that of the positive metal mask is used to form magnetic portion 20 in a region other than the external electrode portion 6 on the surface of the magnetic sheet 200 (step (5c)). The magnetic paste for forming the magnetic portion used in this step may be selected from within the same range as the magnetic paste used in step (1). The conductive paste for forming the external electrode portion used in this step may be selected from within the same range as the conductor paste for forming the via portion used in step (4). In the manufacturing method of the first sheet C, since the pad portion 95 formed in step (4) forms the external electrode portion 6, it is formed wider than the pad portion in step (4) of sheet process Ib.

[0053] After forming the conductor portion and the magnetic portion, it is inverted (step (6b)), and by peeling the base material 90, the first sheet C can be obtained.

[0054] In the first sheet C, the diameter D5 (see FIG. 6(C)) of the via portion 4 (the third via portion) is not particularly limited, and for example, it may be a value within the same range as the diameter D1 of the via portion 4 (the first via portion) in the first sheet A. The diameter D5 of the via portion 4 is the average value of the minimum diameters of each of any 10 via portions in cross-sectional view. Here too, when the member does not have a circular shape in plan view, the diameter may be the width.

[0055] In the first sheet C, the thickness T5 (see FIG. 6(C)) of the via portion 4 (third via portion) is not particularly limited, and may be, for example, a value within the same range as the thickness T1 of the via portion 4 (first via portion) in the first sheet A. The thickness T5 of the via portion 4 is the average value of the minimum thicknesses of each of any 10 via portions in a cross-sectional view.

[0056] In the first sheet C, the width D6 (see FIG. 6(C)) of the external electrode portion 6 is usually 300 μm or more and 600 μm or less, and may particularly be 450 μm or more and 500 μm or less. The width D6 of the external electrode portion 6 is the average value of the widths of any 10 external electrode portions in a cross-sectional view.

[0057] In the first sheet C, the thickness T6 (see FIG. 6(C)) of the external electrode portion 6 is usually 5 μm or more and 50 μm or less, and may particularly be 15 μm or more and 25 μm or less. The thickness T6 of the external electrode portion 6 is the average value of the minimum thicknesses of each of any 10 external electrode portions in a cross-sectional view.

[0058] (Second sheet) FIG. 5 is a flowchart showing steps for explaining a method of manufacturing a second sheet used in the method of manufacturing the laminated inductor of the present disclosure. The second sheet is a through-sheet manufactured by penetrating a base material during manufacturing, and is shown in step (7) of FIG. 5. The second sheet is represented by the symbol "II" in FIGS. 2, 3, 5, and 6, for example.

[0059] The second sheet is a magnetic sheet having a through-hole 5 that penetrates the second sheet in the thickness direction. The through-hole 5 of the second sheet may be a via hole or both a via hole and a through-hole, depending on the arrangement of the second sheet. Specifically, the second sheet may have one or more via holes 4 or one or more through-holes, or may have one or more via holes 4 and one or more through-holes. On one surface (particularly the upper surface) of the second sheet and on the other surface (particularly the lower surface), the surface (exposed surface) of the through-hole 5 is usually flush with the surface (exposed surface) of the magnetic sheet 200. In the present disclosure, since the second sheet is manufactured by penetrating the base material as described later, the magnetic sheet 200 can be formed as a thicker magnetic layer. Therefore, the second sheet is useful for forming a through-hole on the exterior side in the stacking direction T that is outside the layer in which the coil conductor must be wound, and the number of stacked layers during manufacturing can be reduced.

[0060] As shown in FIG. 5, the second sheet is manufactured by the following method. First, a magnetic sheet 200 is formed as a magnetic layer on a base material 90 (step (1)). The thickness K2 of the magnetic sheet is not particularly limited, and may be, for example, 20 μm or more and 100 μm or less, particularly 40 μm or more and 50 μm or less. The method of forming the magnetic layer is not particularly limited, and the magnetic layer may be formed by the same method as the method of forming the magnetic layer for manufacturing the first sheet. The material of the base material 90 is not particularly limited and may be selected from within the same range as the material of the base material for manufacturing the first sheet. The thickness of the base material 90 is not particularly limited as long as the magnetic sheet (magnetic layer) 200 can be transported and peeled from the magnetic layer, and may be selected from within the same range as the thickness of the base material for manufacturing the first sheet, for example.

[0061] Next, a portion of the magnetic sheet 200 corresponding to the through-hole described later is selectively removed from the magnetic sheet side by laser irradiation (step (2)). At this time, the base material 90 is penetrated and opened. Since a laser is used to form the through-hole in this way, the through-hole has a tapered shape in cross-section. Further, since it is inverted in a subsequent step, the through-hole has a tapered shape with a smaller upper side in cross-section. For example, when the through-hole has a circular shape in plan view, it has a frustum of a cone shape as a whole (especially a frustum of a cone shape in which the area of the upper surface is smaller than the area of the bottom surface).

[0062] After the selective removal, it is inverted (step (3)), and another base material 97 is disposed on the laser irradiation side of the magnetic sheet 200 to seal the opening formed by the laser irradiation (step (4)). The material of the base material 97 is not particularly limited and may be selected from within the same range as the material of the base material for manufacturing the first sheet. The thickness of the base material 97 is not particularly limited as long as the magnetic sheet (magnetic layer) 200 can be transported and peeled off from the magnetic layer.

[0063] After the arrangement of the base material 97, a positive metal mask 92 is used, and the through-hole 5 is formed in the removed portion 98 of the magnetic sheet 200 by the screen printing method (steps (5) and (6)). A conductive paste is used in the screen printing method for forming the through-hole. The conductive paste for forming the through-hole used in this step may be selected from within the same range as the conductive paste for forming the via portion used in step (4) during the manufacture of the first sheet. In the above step (5) during the manufacture of the second sheet, since it is difficult to align the positive metal mask 92 strictly only with the region other than the removed portion 98, a pad portion 99 is usually formed around the through-hole 5 in plan view in this step (6).

[0064] After the through-hole is formed, the second sheet can be obtained by peeling off the base materials 90 and 97. In the manufacturing method of the second sheet, since the base material 90 is peeled off after the manufacture of the pad portion 99, the pad portion 99 is removed together with the base material.

[0065] In the second sheet, the thickness T7 of the through-hole 5 (see FIG. 6(D)) is thicker than the thickness T1 of the via 4 in the first sheet A. Specifically, the thickness T7 of the through-hole 5 (see FIG. 6(D)) in each of the second sheets constituting the stacked inductor is thicker than the thickness T1 of the via 4 in any of the first sheets A among all the first sheets A constituting the stacked inductor. As a result, the second sheet becomes more useful for forming the through-hole and can further reduce the number of stacked layers during manufacturing, so that the reliability of electrical connection during stacking can be further enhanced.

[0066] The thickness T7 of the through-hole 5 is the average value of the minimum thicknesses of each of any 10 through-holes in a cross-sectional view. The thickness T7 is not particularly limited and may be a value within the same range as the thickness K2 of the magnetic sheet in the second sheet described above. The thickness T1 of the via 4 is the thickness T1 of the via 4 described above.

[0067] The diameter D7 of the through-hole 5 (see FIG. 6(D)) is not particularly limited and may be, for example, 100 μm or more and 300 μm or less, particularly 120 μm or more and 180 μm or less. The diameter D7 of the through-hole 5 is the average value of the minimum diameters of each of any 10 through-holes in a cross-sectional view. Here too, when the member does not have a circular shape in a plan view, the diameter may be the width.

[0068] (Stacked group) The stacked inductor 1 may be configured by stacking and firing stacked groups G1 to G12.

[0069] The stacked group G1 includes only the pattern layer n1 and has the magnetic portion 20 as a magnetic layer, and constitutes the second main surface B2 of the element 2. The magnetic layer as the stacked group G1 may be formed by any method, for example, by a printing method or by stacking magnetic sheets. The magnetic sheet can be manufactured, for example, by peeling off a magnetic layer formed on a substrate by a printing method such as a screen printing method from the substrate.

[0070] The stacked group G2 includes only the pattern layer n2. The pattern layer n2 has a conductor portion 30 that constitutes the first coil (31) in the magnetic portion 20 (or magnetic sheet). The conductor portion 30 of the stacked group G2 constitutes approximately one turn of the first coil. More specifically, the conductor portion 30 is arranged along the substantially outer peripheral edge of the magnetic layer.

[0071] The stacked group G3 includes the pattern layers n3 and n4, and these pattern layers are pre-integrated prior to stacking with other stacked groups. The pattern layer n3 has a via portion 4 for electrically connecting the conductor portion 30 of the pattern layer n2 and the conductor portion 30 of the pattern layer n4 in the magnetic portion 20 (or magnetic sheet), and a through portion 5 for electrically connecting the conductor portion 30 of the pattern layer n2 and the external electrode portion 6 (E1) disposed on the bottom surface. The pattern layer n4 has a conductor portion 30 that constitutes the first coil (31) in the magnetic portion 20 (or magnetic sheet), and a through portion 5 for electrically connecting the conductor portion 30 of the pattern layer n2 and the external electrode portion 6 (E1) disposed on the bottom surface. The stacked group G3 may be constituted by the first sheet A. The stacked group G3 (particularly the conductor portion 30 of the pattern layer n4) constitutes approximately one turn of the first coil. More specifically, in the pattern layer n4, the conductor portion 30 is arranged along the substantially outer peripheral edge of the magnetic layer.

[0072] The stacked group G4 includes the pattern layers n5 and n6, and these pattern layers are pre-integrated prior to stacking with other stacked groups. The pattern layer n5 is the same as the pattern layer n3 of the stacked group G3 except that the arrangements of the via portions 4 are different from each other. The pattern layer n6 is the same as the pattern layer n4 of the stacked group G3 except that the pattern shapes of the conductor portions 30 that constitute the first coil (31) are different from each other. The stacked group G4 may be constituted by the first sheet A. The conductor portion 30 of the stacked group G4 (particularly the pattern layer n6) constitutes approximately 0.5 turn of the first coil.

[0073] The stacked group G5 includes only the pattern layer n7. The pattern layer n7 has a through-hole 5 for electrically connecting the conductor portion 30 of the pattern layer n2 and the external electrode portion 6 (E1) disposed on the bottom surface in the magnetic portion 20 (or magnetic sheet), and a through-hole 5 for electrically connecting the conductor portion 30 of the pattern layer n6 and the external electrode portion 6 (E2) disposed on the bottom surface. The stacked group G5 may be constituted by the first sheet B.

[0074] The stacked group G6 includes the pattern layers n8 and n9, and these pattern layers are pre-integrated prior to stacking with other stacked groups. The pattern layer n8 is the same as the pattern layer n7 of the stacked group G5. The pattern layer n9 has a conductor portion 30 constituting the second coil (32), a through-hole 5 for electrically connecting the conductor portion 30 of the pattern layer n2 and the external electrode portion 6 (E1) disposed on the bottom surface in the magnetic portion 20 (or magnetic sheet), and a through-hole 5 for electrically connecting the conductor portion 30 of the pattern layer n6 and the external electrode portion 6 (E2) disposed on the bottom surface. The stacked group G6 may be constituted by the first sheet A. The conductor portion 30 of the stacked group G6 (particularly the pattern layer n9) constitutes approximately 3 / 4 turns of the first coil.

[0075] The stacked group G7 includes pattern layers n10 and n11, and these pattern layers are pre-integrated prior to stacking with other stacked groups. The pattern layer n10 is the same as the pattern layer n8 of the stacked group G6, except that it further has a via portion 4 for electrically connecting the conductor portion 30 of the pattern layer n9 and the conductor portion 30 of the pattern layer n11, and a through portion 5 for electrically connecting the conductor portion 30 of the pattern layer n9 and the external electrode portion 6 (E3) disposed on the bottom surface. The pattern layer n11 has a conductor portion 30 constituting the second coil (32) in the magnetic portion 20 (or magnetic sheet), a through portion 5 for electrically connecting the conductor portion 30 of the pattern layer n9 and the external electrode portion 6 (E3) disposed on the bottom surface, a through portion 5 for electrically connecting the conductor portion 30 of the pattern layer n2 and the external electrode portion 6 (E1) disposed on the bottom surface, and a through portion 5 for electrically connecting the conductor portion 30 of the pattern layer n6 and the external electrode portion 6 (E2) disposed on the bottom surface. The stacked group G7 may be constituted by the first sheet A. The conductor portion 30 of the stacked group G7 (particularly the pattern layer n11) constitutes approximately one turn of the first coil.

[0076] The stacked group G8 includes pattern layers n12 and n13, and these pattern layers are pre-integrated prior to stacking with other stacked groups. The pattern layer n12 is the same as the pattern layer n10 of the stacked group G7. The pattern layer n13 is the same as the pattern layer n11 of the stacked group G7, except that the pattern shapes of the conductor portions 30 constituting the second coil (32) are different from each other. The stacked group G8 may be constituted by the first sheet A. The conductor portion 30 of the stacked group G8 (particularly the pattern layer n13) constitutes approximately one-half turn of the second coil.

[0077] The stacked group G9 includes only the pattern layer n14. The pattern layer n14 is the same as the pattern layer n7 of the stacked group G5, except that it further has a through-hole 5 for electrically connecting the conductor part 30 of the pattern layer n9 and the external electrode part 6 (E3) arranged on the bottom surface, and a through-hole 5 for electrically connecting the conductor part 30 of the pattern layer n13 and the external electrode part 6 (E4) arranged on the bottom surface. The stacked group G9 may be constituted by the first sheet B.

[0078] The stacked group G10 includes only the pattern layer n15. The pattern layer n15 has a through-hole 5 for electrically connecting the conductor part 30 of the pattern layer n2 and the external electrode part 6 (E1) arranged on the bottom surface, a through-hole 5 for electrically connecting the conductor part 30 of the pattern layer n6 and the external electrode part 6 (E2) arranged on the bottom surface, a through-hole 5 for electrically connecting the conductor part 30 of the pattern layer n9 and the external electrode part 6 (E3) arranged on the bottom surface, and a through-hole 5 for electrically connecting the conductor part 30 of the pattern layer n13 and the external electrode part 6 (E4) in the magnetic part 20 (or magnetic sheet). The stacked group G10 may be constituted by the second sheet.

[0079] The stacked group G11 includes only the pattern layer n16. The pattern layer n16 is the same as the pattern layer n15 of the stacked group G10. The stacked group G11 may be constituted by the second sheet.

[0080] The stacked group G12 includes only the pattern layer n17. The pattern layer n17 has an external electrode part 6 (E1) electrically connected to the conductor part 30 of the pattern layer n2, an external electrode part 6 (E2) electrically connected to the conductor part 30 of the pattern layer n6, an external electrode part 6 (E3) electrically connected to the conductor part 30 of the pattern layer n9, and an external electrode part 6 (E4) electrically connected to the conductor part 30 of the pattern layer n13 in the magnetic part 20 (or magnetic sheet). The external electrode parts 6 (E1 to E4) are respectively arranged near the corner of the bottom surface in a plan view in the magnetic part 20 (or magnetic sheet). The stacked group G12 may be constituted by the first sheet C.

[0081] The manufacturing method of the laminated inductor according to the present disclosure is characterized by laminating a plurality of first sheets A.

[0082] For example, as shown in FIGS. 2 and 3, the first sheet A as the lamination group G3 and the first sheet A as the lamination group G4 are laminated. By laminating such two first sheets A, a first coil layer including a first coil (31 in FIG. 1) in which the conductor portion 30 of the lamination group G3 and the conductor portion 30 of the lamination group G4 are electrically connected via the via portion 4 (first via portion) is formed.

[0083] Also, for example, as shown in FIGS. 2 and 3, the first sheet A as the lamination group G6, the first sheet A as the lamination group G7, and the first sheet A as the lamination group G8 are laminated. By laminating such three first sheets A, a second coil layer including a second coil (32 in FIG. 1) in which the conductor portion 30 of the lamination group G6, the conductor portion 30 of the lamination group G7, and the conductor portion 30 of the lamination group G8 are electrically connected via the via portion 4 (first via portion) is formed.

[0084] In the present disclosure, since a plurality of first sheets A corresponding to two sheets in the conventional method are laminated, the number of laminations during manufacturing can be further reduced. Further, since the first sheet A is manufactured without penetrating the base material as described above, the magnetic sheet 200 can be formed as a thinner magnetic layer. Therefore, the first sheet A is useful for adjusting the thickness of the base body (particularly each pattern layer constituting the base body). Furthermore, since the first sheet A can be manufactured using only one base material per sheet, it is excellent in manufacturing cost. Furthermore, by using the first sheet A, a thinner via portion can be formed and a thicker conductor portion can be formed with a limited size of the base body, so that the characteristics of the inductor can be improved.

[0085] In the present disclosure, it is preferable to further laminate one or more second sheets below the first coil layer to form a through-conductor layer. Thereby, the through-conductor layer can have through-holes that penetrate the one or more second sheets, and the through-holes are electrically connected to both ends of the first coil of at least the first coil layer. Since the second sheet is manufactured by penetrating the base material as described above, the magnetic sheet 200 can be formed as a thicker magnetic layer. Therefore, the second sheet is more useful for forming the through-holes and can further reduce the number of laminated layers during manufacturing.

[0086] Specifically, as shown in FIGS. 2 and 3, the second sheet as the lamination group G10 and the second sheet as the lamination group G11 are further laminated below the coil layer.

[0087] For example, when the laminated inductor has only one coil layer, the one or more second sheets are laminated below the coil layer to form a through-conductor layer. At this time, the number of through-holes that penetrate the one or more second sheets in the through-conductor layer is usually two. Such two through-holes are electrically connected to both ends of the first coil of the first coil layer. Specifically, one of the two through-holes is electrically connected to one end of the first coil, and the other through-hole is electrically connected to the other end of the first coil. Thereby, the electrical connection between both ends of the first coil and the external electrode portion on the bottom surface of the element body is achieved.

[0088] For example, when the stacked inductor has two coil layers (i.e., the first coil layer and the second coil layer) as shown in FIGS. 2 and 3, the one or more second sheets are stacked below the coil layer (the second coil layer in FIGS. 2 and 3) that is disposed at the lowermost position among the two or more coil layers, and a through-conductor layer is formed. At this time, the number of through-holes penetrating the one or more second sheets in the through-conductor layer is usually four. These four through-holes are electrically connected to both ends (C1s, C1e) of the first coil of the first coil layer and both ends (C2s, C2e) of the second coil of the second coil layer. Specifically, each of both ends (C1s, C1e) of the first coil and both ends (C2s, C2e) of the second coil is electrically connected to the external electrode portions 6 (E1, E2, E3, E4) via one of the four through-holes.

[0089] In the present disclosure, it is preferable to further stack the first sheet C below the through-conductor layer to form an external electrode portion layer. Thereby, the external electrode portions 6 are electrically connected to the through-holes of the through-conductor layer via the third via portions. The number of stacked first sheets C is usually one. Since the first sheet C corresponds to two sheets in the conventional method, the number of stacked layers during manufacturing can be further reduced. Also, by using the first sheet C, the external electrode portions can be formed thinly with a limited element size, so that the characteristics of the inductor can be improved. Furthermore, since the first sheet C can be manufactured using only one base material as shown in the manufacturing method described later for each sheet, the first sheet C is also excellent in manufacturing cost like the first sheet A.

[0090] Specifically, as shown in FIGS. 2 and 3, the first sheet C as the stacked group G12 is further stacked below the through-conductor layer.

[0091] For example, when the stacked inductor has only one coil layer, usually, for each sheet, a sheet 1c having two external electrode portions is stacked below the through-hole portion to form an external electrode portion layer. At this time, the two external electrode portions are electrically connected to both ends of the first coil of the first coil layer. Specifically, one of the two external electrode portions is electrically connected to one end of the first coil, and the other external electrode portion is electrically connected to the other end of the first coil. Thereby, the electrical connection between both ends of the first coil and the external electrode portions is achieved.

[0092] Also, for example, when the stacked inductor has two coil layers (i.e., the first coil layer and the second coil layer) as shown in FIGS. 2 and 3, usually, for each sheet, a first sheet C having four external electrode portions is stacked below the through-hole portion to form an external electrode portion layer. At this time, the four external electrode portions 6 (E1, E2, E3, E4) are electrically connected to both ends (C1s, C1e) of the first coil of the first coil layer and both ends (C2s, C2e) of the second coil of the second coil layer through one of the four through-hole portions, respectively.

[0093] In the present disclosure, as shown in FIGS. 2 and 3, it is preferable to form a coil intermediate layer and a second coil layer between the first coil layer and the through-conductor layer. Thereby, a 2-in-1 inductor can be obtained, and the characteristics of the inductor can be further improved with a limited element size.

[0094] Specifically, the second coil layer is formed to include a second coil in which conductor portions are electrically connected through first via portions in the plurality of first sheets A by further stacking a plurality of first sheets A selected from within the same range as the first sheet A forming the first coil layer.

[0095] For example, as shown in FIGS. 1 to 3, the second coil layer is formed to include a second coil (32 in FIG. 1) in which a conductor portion 30 is electrically connected through via portions 4 (first via portions) in the three first sheets A as a stacked group G6 to 8.

[0096] The second coil layer usually includes one or more additional first sheets B laminated below (or immediately below) the laminate of the plurality of additional first sheets A as shown in FIGS. 1 to 3. The second coil of the second coil layer and the through-hole portion of the through-conductor layer are electrically connected through the via portion 4 (second via portion) (or through-hole portion 5) of the one or more additional first sheets B.

[0097] The inter-coil layer is formed by laminating one or more (preferably one) first sheets B below (or immediately below) the first coil layer (particularly between the first coil layer and the second coil layer). Through the through-hole portion of the inter-coil layer, electrical connection between both ends of the first coil of the first coil layer and the external electrode portion on the bottom surface of the element body is achieved. By forming the inter-coil layer, sufficient insulation between the first coil and the second coil can be ensured.

[0098] For example, as shown in FIGS. 1 to 3, the inter-coil layer is formed by laminating one or more (preferably one) first sheets B as the lamination group G5 below (or immediately below) the first coil layer (particularly between the first coil layer and the second coil layer).

[0099] In the laminated inductor of the present disclosure, the thickness M (see FIG. 3) of the inter-coil layer is preferably greater than the distance L1 between the conductor portions 30 of the first coil in the first coil layer and the distance L2 between the conductor portions of the second coil in the second coil layer. By satisfying such a relationship, further sufficient insulation between the first coil and the second coil can be ensured.

[0100] The thickness M of the inter-coil layer refers to the distance between coils. Specifically, it is the distance between the lowermost conductor part 30 of the coil (for example, the first coil) arranged above the inter-coil layer and the uppermost conductor part 30 of the coil (for example, the second coil) arranged below the inter-coil layer. The thickness M of the inter-coil layer uses the average value of the thickness M of the inter-coil layer at any 10 locations in a cross-sectional view. The thickness M is not particularly limited and may be, for example, 20 μm or more and 60 μm or less, particularly 30 μm or more and 40 μm or less.

[0101] The distance L1 between the conductor parts 30 of the first coil uses the average value of the distance L1 at any 10 locations in a cross-sectional view. The distance L1 is not particularly limited and may be, for example, 10 μm or more and 40 μm or less, particularly 15 μm or more and 25 μm or less.

[0102] The distance L2 between the conductor parts 30 of the second coil uses the average value of the distance L2 at any 10 locations in a cross-sectional view. The distance L2 is not particularly limited and may be, for example, a value within the same range as the distance L1 between the conductor parts 30 of the first coil described above.

[0103] After stacking the desired stacking group to obtain an unfired green body precursor, the unfired green body precursor is usually pressure-treated to obtain a laminate. The method of pressure treatment is not particularly limited and may be, for example, a press treatment method such as warm isostatic pressing (WIP). After the pressure treatment, the laminate is usually placed in a firing furnace, degreased, and then fired in the atmosphere. The firing temperature is not particularly limited and may be, for example, 600 °C or more and 800 °C or less. The firing time is not particularly limited and may be, for example, 30 minutes or more and 300 minutes or less.

[0104] After obtaining a green body by firing, an exterior resin layer may be formed on the surface of the green body. The exterior resin layer may usually be formed in a region other than the surface of the external electrode part at the bottom surface on the surface of the green body. The material constituting the exterior resin layer is not particularly limited as long as it protects the green body and may be any known polymer.

[0105] The technical scope of the present disclosure is not construed only by the above-described embodiments, but is defined based on the description of the claims. Further, the technical scope of the present disclosure includes all modifications within the meaning and scope equivalent to the claims.

[0106] The laminated inductor of the present disclosure and its manufacturing method include the following aspects. <1> Prepare a plurality of first sheets A each having a conductor portion and a magnetic portion formed on the lower side of a magnetic sheet, and a first via portion penetrating the magnetic sheet above the conductor portion. A method for manufacturing a laminated inductor, comprising laminating the plurality of first sheets A to form a first coil layer including a first coil in which the conductor portions are electrically connected via the first via portions. <2> The method for manufacturing a laminated inductor according to <1>, wherein in each of the first sheets A, the diameter D1 of the first via portion is narrower than the width D2 of the conductor portion. <3> The method for manufacturing a laminated inductor according to <1> or <2>, wherein in each of the first sheets A, the thickness T1 of the first via portion is thinner than the thickness T2 of the conductor portion. <4> The method for manufacturing a laminated inductor according to any one of <1> to <3>, wherein in each of the first sheets A, the first via portion has a tapered shape in which the upper width is smaller than the lower width in a cross-sectional view. <5> Further, prepare a second sheet having a through portion. Laminating one or more of the second sheets further under the first coil layer to form a through conductor layer. The method for manufacturing a laminated inductor according to any one of <1> to <4>, wherein the through portion is electrically connected to both ends of the first coil. <6> The method for manufacturing a laminated inductor according to <5>, wherein the thickness T7 of the through portion in each of the second sheets is thicker than the thickness T1 of the first via portion in the first sheet A. <7> Form a coil intermediate layer and a second coil layer between the first coil layer and the through conductor layer. The second coil layer is formed to include a second coil in which a conductor portion is electrically connected via the first via portion by further laminating a plurality of additional first sheets A. Prepare a first sheet B having a second via portion penetrating the magnetic sheet, and having a flange-shaped conductor portion formed around the second via portion on the lower side of the magnetic sheet and a magnetic portion formed further around the flange-shaped conductor portion. The method for manufacturing a laminated inductor according to <5> or <6>, wherein the inter-coil layer is formed by laminating one or more of the first sheets B. <8> The method for manufacturing a laminated inductor according to <7>, wherein a thickness M of the inter-coil layer is thicker than a distance L1 between the conductor portions of the first coil and a distance L2 between the conductor portions of the second coil. <9> The method for manufacturing a laminated inductor according to <7> or <8>, wherein in each of the first sheets B, a diameter D3 of the second via portion is narrower than a width D40 of the flange-shaped conductor portion. Further laminate a first sheet C under the through-conductor layer to form an external electrode portion layer. The first sheet C has an external electrode portion and a magnetic portion formed under the magnetic sheet, and a third via portion penetrating the magnetic sheet above the external electrode portion. The method for manufacturing a laminated inductor according to any one of <7> to <9>, wherein the external electrode portion is electrically connected to the through portion via the third via portion. <11> The method for manufacturing a laminated inductor according to <10>, wherein the third via portion has a tapered shape in a cross-sectional view in which an upper width is smaller than a lower width.

Industrial Applicability

[0107] The present disclosure can be used for a method for manufacturing a laminated inductor with a reduced number of laminations.

Explanation of Signs

[0108] 1 Laminated inductor 2 Element body 3 Coil 4 Via portion 5 Through-hole part 6 External electrode part 20 Magnetic part 30 Conductor part

Claims

1. A plurality of first sheets A are prepared, each having a conductor portion and a magnetic portion formed on a lower side of a magnetic sheet, and a first via portion penetrating the magnetic sheet above the conductor portion; A method for manufacturing a laminated inductor, comprising stacking the plurality of first sheets A to form a first coil layer including a first coil to which the conductor portion is electrically connected through the first via portion.

2. 2. The method for manufacturing a laminated inductor according to claim 1, wherein in each of said first sheets A, a diameter D1 of said first via portion is narrower than a width D2 of said conductor portion.

3. 2. The method for manufacturing a laminated inductor according to claim 1, wherein in each of said first sheets A, a thickness T1 of said first via portion is thinner than a thickness T2 of said conductor portion.

4. 2. The method for manufacturing a laminated inductor according to claim 1, wherein in each of said first sheets A, said first via portion has a tapered shape in which an upper side width is smaller than a lower side width in a cross-sectional view.

5. Further, a second sheet having a through-hole is prepared; One or more of the second sheets are further laminated on the lower side of the first coil layer to form a through conductor layer; The method for manufacturing a laminated inductor according to claim 1 , wherein the through portion is electrically connected to both ends of the first coil.

6. The method for manufacturing a laminated inductor according to claim 5 , wherein a thickness T7 of the through portion in each of the second sheets is greater than a thickness T1 of the first via portion in the first sheet A.

7. a coil interlayer and a second coil layer are formed between the first coil layer and the through conductor layer; the second coil layer is formed by laminating a plurality of the first sheets A so as to include a second coil to which the conductor portion is electrically connected through the first via portion, preparing a first sheet B having a second via portion penetrating a magnetic sheet, and having a flange-shaped conductor portion formed around the second via portion on the lower side of the magnetic sheet, and a magnetic portion formed around the flange-shaped conductor portion; The method for manufacturing a laminated inductor according to claim 5 , wherein the inter-coil layer is formed by laminating one or more of the first sheets B.

8. The method for manufacturing a laminated inductor according to claim 7 , wherein a thickness M of the inter-coil layer is greater than a distance L1 between the conductor portions of the first coil and a distance L2 between the conductor portions of the second coil.

9. 8. The method for manufacturing a laminated inductor according to claim 7, wherein in each of said first sheets B, a diameter D3 of said second via portion is narrower than a width D40 of said flange-shaped conductor portion.

10. A first sheet C is further laminated on the lower side of the through conductor layer to form an external electrode layer; the first sheet C has an external electrode portion and a magnetic portion formed on a lower side of a magnetic sheet, and a third via portion penetrating the magnetic sheet on an upper side of the external electrode portion, The method for manufacturing a multilayer inductor according to claim 7 , wherein the external electrode portion is electrically connected to the through portion through the third via portion.

11. The method for manufacturing a multilayer inductor according to claim 10 , wherein the third via portion has a tapered shape in which an upper width is smaller than a lower width in a cross-sectional view.

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