Coil device and method for manufacturing coil device

Abstract

This coil device is provided with: a first base film that has a first main surface and a second main surface; a first wiring that is disposed on the first main surface and has a first coil section which is wound in a spiral shape in a plan view; a second wiring that is disposed on the second main surface and has a second coil section which is wound in the spiral shape in the plan view; a first resin layer that is disposed on the first main surface in a manner so as to cover the first wiring; and a second resin layer that is disposed on the second main surface in a manner so as to cover the second wiring. The first resin layer has: a first surface that faces the first main surface; and a second surface that is the reverse surface of the first surface. The second resin layer has: a third surface that faces the second main surface; and a fourth surface that is the reverse surface of the third surface. A value obtained by subtracting the minimum value of the distance between the second surface and the fourth surface from the maximum value of the distance between the second surface and the fourth surface is 20% or less of the maximum value of the distance between the second surface and the fourth surface.

Description

Coil device and method for manufacturing the same

[0001] The present disclosure relates to a coil device and a method for manufacturing a coil device. This application claims priority to Japanese Patent Application No. 2024-000246, filed on January 4, 2024. The entire contents of the Japanese patent application are incorporated herein by reference.

[0002] For example, Japanese Patent Laid-Open Publication No. 2021-174794 (Patent Document 1) describes a coil device. The coil device described in Patent Document 1 includes a base film, a first wiring, and a second wiring.

[0003] The base film has a first main surface and a second main surface. The second main surface is the surface opposite to the first main surface. The first wiring is disposed on the first main surface. The first wiring has a first coil portion that is spirally wound in a plan view. The second wiring is disposed on the second main surface. The second wiring has a second coil portion that is spirally wound in a plan view.

[0004] Japanese Patent Application Laid-Open No. 2021-174794

[0005] The coil device of the present disclosure includes a first base film having a first main surface and a second main surface opposite the first main surface, a first wiring disposed on the first main surface and having a first coil portion wound in a spiral shape in a plan view, and a first resin layer disposed on the first main surface so as to cover the first wiring. The first resin layer has a first surface opposite the first main surface and a second surface opposite the first surface. The value obtained by subtracting the minimum value of the distance between the second surface and the second main surface from the maximum value of the distance between the second surface and the second main surface is 10% or less of the maximum value of the distance between the second surface and the second main surface.

[0006] FIG. 1 is a first plan view of the coil device 100. FIG. 2 is a second plan view of the coil device 100 as viewed from the opposite side to FIG. 1. FIG. 3 is a third plan view of the coil device 100, in which the first resin layer 30 and the third wiring 40 are omitted. FIG. 4 is a fourth plan view of the coil device 100 as viewed from the opposite side to FIG. 3, in which the second resin layer 31 and the fourth wiring 41 are omitted. FIG. 5 is a cross-sectional view taken along line V-V in FIG. 1. FIG. 6 is a manufacturing process diagram of the coil device 100. FIG. 7 is a cross-sectional view illustrating the conductive treatment step S2. FIG. 8 is a cross-sectional view illustrating the resist pattern formation step S3. FIG. 9 is a cross-sectional view illustrating the electroplating step S4. FIG. 10 is a cross-sectional view illustrating the resist pattern removal step S5. FIG. 11 is a cross-sectional view illustrating the etching step S6. FIG. 12 is a cross-sectional view illustrating the heat pressing step S7. FIG. 13 is a cross-sectional view illustrating the conductive treatment step S8. FIG. 14 is a cross-sectional view illustrating the resist pattern formation step S9. FIG. 15 is a cross-sectional view illustrating the electroplating step S10. FIG. 16 is a cross-sectional view illustrating the resist pattern removing step S11.

[0007] [Problem to be Solved by the Present Disclosure] In order to improve the coil characteristics (inductance) of the coil device described in Patent Document 1, it is conceivable to further stack the coil portion. More specifically, first, a first resin layer is disposed on the first main surface so as to cover the first wiring, and a second resin layer is disposed on the second main surface so as to cover the second wiring. At this time, the first resin layer and the second resin layer are attached to the base film by heat pressing. Note that conductive layers are formed on the surfaces of the first resin layer and the second resin layer.

[0008] Second, a dry film resist is applied to the conductive layer, and the dry film resist is exposed and developed to form a resist pattern. The resist pattern has openings that expose the conductive layer. Third, electrolytic plating is performed on the portions of the conductive layer exposed from the openings to form an electrolytic plated layer. Fourth, the resist pattern is removed. Fifth, the conductive layer underneath the resist pattern is removed by etching. As a result, a third wiring composed of the conductive layer and the electrolytic plated layer is formed on the first resin layer, and a third wiring composed of the conductive layer and the electrolytic plated layer is formed on the second resin layer.

[0009] If there are portions where the distance between the surface of the first resin layer and the surface of the second resin layer is small, the resist pattern formed on the first resin layer and the second resin layer may have portions where the thickness is large. Furthermore, if there are portions where the distance between the surface of the first resin layer and the surface of the second resin layer is small, the exposure of the dry film resist may be hindered, resulting in deformation of the cross-sectional shape of the wiring and fluctuations in the wiring spacing and wiring width. Furthermore, if there are portions where the distance between the surface of the first resin layer and the surface of the second resin layer is small, the removal of the resist pattern may be hindered, resulting in defects in the wiring. If there are portions where the distance between the surface of the first resin layer and the surface of the second resin layer is large, the resist pattern formed on the first resin layer and the second resin layer may have portions where the thickness is small, resulting in the wiring thickness being larger than the thickness of the resist pattern, which may cause deformation of the cross-sectional shape of the wiring or short circuits between adjacent wiring. As a result, it may be impossible to properly form wiring (third wiring, fourth wiring) on ​​the resin layer (first resin layer, second resin layer).

[0010] The present disclosure provides a coil device that allows wiring to be appropriately formed on a resin layer.

[0011] [Effects of the Present Disclosure] According to the coil device of the present disclosure, it is possible to appropriately form wiring on the resin layers (first resin layer, second resin layer).

[0012] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described.

[0013] (1) A coil device according to one embodiment of the present disclosure includes a first base film having a first main surface and a second main surface opposite the first main surface, a first wiring disposed on the first main surface and having a first coil portion wound in a spiral shape in a plan view, and a first resin layer disposed on the first main surface so as to cover the first wiring. The first resin layer has a first surface opposite the first main surface and a second surface opposite the first surface. The value obtained by subtracting the minimum value of the distance between the second surface and the second main surface from the maximum value of the distance between the second surface and the second main surface is 10% or less of the maximum value of the distance between the second surface and the second main surface. The coil device described in (1) above allows wiring to be appropriately formed on the resin layer.

[0014] (2) In the coil device described above in (1), the maximum value of the distance between the second surface and the second main surface may be 65 μm or more.

[0015] (3) A coil device according to another embodiment of the present disclosure includes a first base film having a first main surface and a second main surface opposite the first main surface, a first wiring arranged on the first main surface and having a first coil portion wound in a spiral shape in a plan view, a second wiring arranged on the second main surface and having a second coil portion wound in a spiral shape in a plan view, a first resin layer arranged on the first main surface to cover the first wiring, and a second resin layer arranged on the second main surface to cover the second wiring. The first resin layer has a first surface opposite the first main surface and a second surface opposite the first surface. The second resin layer has a third surface opposite the second main surface and a fourth surface opposite the third surface. The value obtained by subtracting the minimum value of the distance between the second surface and the fourth surface from the maximum value of the distance between the second surface and the fourth surface is 20 percent or less of the maximum value of the distance between the second surface and the fourth surface. According to the coil device of (3) above, it is possible to appropriately form wiring on the resin layer.

[0016] (4) In the coil device of (3) above, the maximum distance between the second surface and the fourth surface may be 125 μm or more.

[0017] (5) In the coil device of (1) or (2), the area of ​​the portion of the first main surface on which the first wiring is arranged may be 90 percent or less of the area of ​​the first main surface. According to the coil device of (5), it is possible to appropriately form wiring on the resin layer (first resin layer).

[0018] (6) In the coil device of (3) or (4) above, the area of ​​the portion of the first main surface on which the first wiring is arranged may be 90 percent or less of the area of ​​the first main surface. The area of ​​the portion of the second main surface on which the second wiring is arranged may be 90 percent or less of the area of ​​the second main surface. According to the coil device of (6) above, it is possible to appropriately form wiring on the resin layer (first resin layer, second resin layer).

[0019] (7) The coil device according to any one of (1) to (6) above may further include a third wiring disposed on the second surface. The third wiring may include a conductive layer disposed on the second surface and an electroplated layer disposed on the conductive layer. According to the coil device according to (7) above, it is possible to appropriately form the wiring (third wiring) on ​​the resin layer (first resin layer).

[0020] (8) In the coil device of (7), the height of the third wiring may be 45 μm or more. According to the coil device of (8), it is possible to appropriately form the wiring (third wiring) on ​​the resin layer (first resin layer).

[0021] (9) In the coil device of (7) or (8), the spacing between adjacent third wirings may be 15 μm or less. According to the coil device of (9), it is possible to appropriately form wirings (third wirings) on the resin layer (first resin layer).

[0022] (10) A method for manufacturing a coil device according to an embodiment of the present disclosure includes the steps of: preparing a first base film having a first main surface and a second main surface opposite the first main surface; forming a first wiring having a first coil portion wound in a spiral shape in a plan view on the first main surface; arranging a first resin layer on the first main surface so as to cover the first wiring; and sandwiching the first base film, the first wiring, and the first resin layer between a first plate member and a second plate member and performing a heat press. Only a release layer is disposed between the first plate member and the first resin layer and between the second plate member and the second main surface. The method for manufacturing a coil device according to (10) above allows the wiring to be appropriately formed on the resin layer.

[0023] (11) A method for manufacturing a coil device according to another embodiment of the present disclosure includes the steps of: preparing a first base film having a first main surface and a second main surface opposite the first main surface; forming a first wiring having a first coil portion wound spirally in a plan view and a second wiring having a second coil portion wound spirally in a plan view on the first main surface and the second main surface, respectively; disposing a first resin layer on the first main surface so as to cover the first wiring and a second resin layer on the second main surface so as to cover the second wiring; and sandwiching the first base film, the first wiring, the second wiring, the first resin layer, and the second resin layer between a first plate member and a second plate member and performing a heat press. Only a release layer is disposed between the first plate member and the first resin layer and between the second plate member and the second resin layer. The method for manufacturing a coil device according to (11) above allows wiring to be appropriately formed on the resin layers (first resin layer, second resin layer).

[0024] (12) In the coil device manufacturing method of (10) or (11) above, the first resin layer may have a first surface facing the first main surface and a second surface opposite the first surface. A conductive layer may be disposed on the second surface. The coil device manufacturing method of (12) above may further include the steps of: applying a dry film resist to the conductive layer and exposing and developing the dry film resist to form a resist pattern having openings exposing the conductive layer; forming an electroplated layer by electroplating on the portions of the conductive layer exposed from the openings; removing the resist pattern; and etching away the portions of the conductive layer that were underneath the resist pattern. The coil device manufacturing method of (12) above allows wiring to be appropriately formed on the resin layer.

[0025] [Details of the embodiment of the present disclosure] The details of the embodiment of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and redundant description will not be repeated. The coil device according to the embodiment is referred to as coil device 100.

[0026] (Configuration of Coil Device 100) The configuration of the coil device 100 will be described below.

[0027] FIG. 1 is a first plan view of the coil device 100. FIG. 2 is a second plan view of the coil device 100 seen from the opposite side to FIG. 1. FIG. 3 is a third plan view of the coil device 100, in which the first resin layer 30 and the third wiring 40 are omitted. FIG. 4 is a fourth plan view of the coil device 100 seen from the opposite side to FIG. 3, in which the second resin layer 31 and the fourth wiring 41 are omitted. FIG. 5 is a cross-sectional view taken along line VV in FIG. 1. As shown in FIGS. 1 to 5, the coil device 100 has a first base film 10, a first wiring 20, a second wiring 21, a first resin layer 30, a second resin layer 31, a third wiring 40, and a fourth wiring 41.

[0028] The first base film 10 is made of a flexible, electrically insulating material. A specific example of the material of the first base film 10 is polyimide. The first base film 10 has a first main surface 10a and a second main surface 10b. The first main surface 10a and the second main surface 10b form the end surfaces of the first base film 10 in the thickness direction. The second main surface 10b is the surface opposite the first main surface 10a.

[0029] The first wiring 20 is disposed on the first main surface 10a. The first wiring 20 has a first coil portion 20a that is wound in a spiral shape in a plan view. One end and the other end of the first wiring 20 are located at the outermost and innermost peripheries of the first coil portion 20a, respectively.

[0030] The second wiring 21 is disposed on the second main surface 10b. The second wiring 21 has a second coil portion 21a that is spirally wound in a plan view. The second coil portion 21a overlaps the first coil portion 20a in a plan view. One end and the other end of the second wiring 21 are located at the outermost and innermost peripheries of the second coil portion 21a, respectively. One end of the first wiring 20 and one end of the second wiring 21 overlap each other in a plan view.

[0031] Each of the first wiring 20 and the second wiring 21 has a conductive layer 22 and an electrolytic plated layer 23 .

[0032] The conductive layer 22 includes, for example, a first layer 22a and a second layer 22b. The first layer 22a is disposed on the main surfaces (first main surface 10a, second main surface 10b) of the first base film 10. The first layer 22a is, for example, a sputtered layer (a layer formed by sputtering). A specific example of the material of the first layer 22a is a nickel-chromium alloy.

[0033] A through hole 10c is formed in the first base film 10 and the first layer 22a. The through hole 10c penetrates the first base film 10 and the first layer 22a in the thickness direction. The through hole 10c is formed at a position overlapping one end of the first wiring 20 and one end of the second wiring 21.

[0034] The second layer 22b is disposed on the first layer 22a. The second layer 22b is also formed on the inner wall surface of the through hole 10c. The second layer 22b is, for example, an electroless plated layer (a layer formed by electroless plating). A specific example of the material of the second layer 22b is copper.

[0035] The electrolytic plated layer 23 is disposed on the conductive layer 22 (second layer 22b). The electrolytic plated layer 23 is a layer formed by electrolytic plating. A specific example of a material for the electrolytic plated layer 23 is copper. The first wiring 20 and the second wiring 21 are electrically connected by the second layer 22b and the electrolytic plated layer 23 disposed on the inner wall surface of the through hole 10c.

[0036] The area of ​​the portion of the first main surface 10a where the first wirings 20 are arranged is preferably 90 percent or less of the area of ​​the first main surface 10a. The area of ​​the portion of the first main surface 10a where the first wirings 20 are arranged is, for example, 40 percent or more of the area of ​​the first main surface 10a. The area of ​​the portion of the second main surface 10b where the second wirings 21 are arranged is preferably 90 percent or less of the area of ​​the second main surface 10b. The area of ​​the portion of the second main surface 10b where the second wirings 21 are arranged is, for example, 40 percent or more of the area of ​​the second main surface 10b.

[0037] The first resin layer 30 is disposed on the first major surface 10a so as to cover the first wiring 20. The first resin layer 30 has a first surface 30a and a second surface 30b. The first surface 30a faces the first major surface 10a. The second surface 30b is the surface opposite to the first surface 30a.

[0038] The first resin layer 30 includes a first adhesive layer 30c and a second base film 30d. The first adhesive layer 30c is disposed on the first main surface 10a so as to cover the first wiring 20. The second base film 30d is disposed on the first adhesive layer 30c. The first adhesive layer 30c and the second base film 30d respectively constitute the first surface 30a and the second surface 30b. A specific example of a material for the first adhesive layer 30c is a thermosetting resin. A specific example of a material for the second base film 30d is polyimide.

[0039] The second resin layer 31 is disposed on the second main surface 10b so as to cover the second wiring 21. The second resin layer 31 has a third surface 31a and a fourth surface 31b. The third surface 31a faces the second main surface 10b. The fourth surface 31b is the surface opposite to the third surface 31a.

[0040] The second resin layer 31 includes a second adhesive layer 31c and a third base film 31d. The second adhesive layer 31c is disposed on the second main surface 10b so as to cover the second wiring 21. The third base film 31d is disposed on the second adhesive layer 31c. The second adhesive layer 31c and the third base film 31d respectively constitute the third surface 31a and the fourth surface 31b. A specific example of a material for the second adhesive layer 31c is a thermosetting resin. A specific example of a material for the third base film 31d is polyimide.

[0041] The distance between the second surface 30b and the fourth surface 31b is defined as the distance DIS. The value obtained by subtracting the minimum value of the distance DIS from the maximum value of the distance DIS is 20 percent or less of the maximum value of the distance DIS. The value obtained by subtracting the minimum value of the distance DIS from the maximum value of the distance DIS may be 5 percent or less of the maximum value of the distance DIS. Note that the value obtained by subtracting the minimum value of the distance DIS from the maximum value of the distance DIS is, for example, 0.1 percent or more of the maximum value of the distance DIS, and is not 0 percent of the maximum value of the distance DIS. The distance DIS is measured by thickness measurement using a micrometer. The distance DIS may also be measured by cross-sectional observation. The maximum value of the distance DIS is, for example, 125 μm or more.

[0042] The third wiring 40 is disposed on the second surface 30b. The third wiring 40 has a third coil portion 40a that is spirally wound in a plan view. The third coil portion 40a overlaps the first coil portion 20a in a plan view. One end and the other end of the third wiring 40 are located at the outermost and innermost peripheries of the third coil portion 40a, respectively. The other end of the first wiring 20 and the other end of the third wiring 40 overlap each other in a plan view.

[0043] The fourth wiring 41 is disposed on the fourth surface 31b. The fourth wiring 41 has a fourth coil portion 41a that is spirally wound in a plan view. The fourth coil portion 41a overlaps the second coil portion 21a in a plan view. One end and the other end of the fourth wiring 41 are located at the outermost and innermost peripheries of the fourth coil portion 41a, respectively. The other end of the second wiring 21 and the other end of the fourth wiring 41 overlap each other in a plan view.

[0044] The distance between adjacent portions of the third wiring 40 is defined as distance SP1. The distance between adjacent portions of the fourth wiring 41 is defined as distance SP2. The distance SP1 and the distance SP2 are preferably 15 μm or less, and more preferably 10 μm or less. The distance SP1 and the distance SP2 are, for example, 1 μm or more. The height of the third wiring 40 is defined as height H1, and the height of the fourth wiring 41 is defined as height H2. The height H1 and the height H2 are preferably 45 μm or more, and more preferably 90 μm or more. The height H1 and the height H2 are, for example, 150 μm or less.

[0045] Each of the third wiring 40 and the fourth wiring 41 includes a conductive layer 42 and an electrolytic plated layer 43 .

[0046] The conductive layer 42 includes, for example, a first layer 42a and a second layer 42b. The first layer 42a of the third wiring 40 is disposed on the second surface 30b, and the first layer 42a of the fourth wiring 41 is disposed on the fourth surface 31b. The first layer 42a is, for example, a sputtered layer. A specific example of the material of the first layer 42a is a nickel-chromium alloy.

[0047] A through hole 30e (not shown) is formed in the first resin layer 30 and the first layer 42a. The through hole 30e penetrates the first resin layer 30 and the first layer 42a in the thickness direction. The through hole 30e is formed at a position overlapping the other end of the first wiring 20 and the other end of the third wiring 40. A through hole 31e (not shown) is formed in the second resin layer 31 and the first layer 42a. The through hole 31e penetrates the second resin layer 31 and the first layer 42a in the thickness direction. The through hole 31e is formed at a position overlapping the other end of the second wiring 21 and the other end of the fourth wiring 41.

[0048] The second layer 42b is disposed on the first layer 42a. The second layer 42b is also formed on the inner wall surface of the through hole 30e, on the other end of the first wiring 20 exposed from the through hole 30e, and on the inner wall surface of the through hole 31e and on the other end of the second wiring 21 exposed from the through hole 31e. The second layer 42b is, for example, an electroless plating layer. A specific example of the material of the second layer 42b is copper.

[0049] The electrolytic plating layer 43 is disposed on the conductive layer 42 (second layer 42b). The electrolytic plating layer 43 is a layer formed by electrolytic plating. A specific example of a material for the electrolytic plating layer 43 is copper. The first wiring 20 and the third wiring 40 are electrically connected by the second layer 42b and the electrolytic plating layer 43, which are disposed on the inner wall surface of the through hole 30e and on the other end of the first wiring 20 exposed from the through hole 30e. The second wiring 21 and the fourth wiring 41 are electrically connected by the second layer 42b and the electrolytic plating layer 43, which are disposed on the inner wall surface of the through hole 31e and on the other end of the second wiring 21 exposed from the through hole 31e.

[0050] <Modifications> Although the above describes an example in which the second wiring 21 is formed on the second main surface 10b, the coil device 100 does not necessarily have to have the second wiring 21 formed thereon. In this case, the value obtained by subtracting the minimum value of the distance between the second surface 30b and the second main surface 10b from the maximum value of the distance between the second surface 30b and the second main surface 10b is 10% or less of the maximum value of the distance between the second surface 30b and the second main surface 10b. In this case, the maximum value of the distance between the second surface 30b and the second main surface 10b may be 65 μm or less.

[0051] (Method of Manufacturing Coil Device 100) A method of manufacturing the coil device 100 will be described below.

[0052] 6 is a manufacturing process diagram of the coil device 100. As shown in Fig. 6, the manufacturing method of the coil device 100 includes a preparation step S1, a conductive treatment step S2, a resist pattern formation step S3, an electrolytic plating step S4, a resist pattern removal step S5, and an etching step S6. The manufacturing method of the coil device 100 further includes a heat pressing step S7, a conductive treatment step S8, a resist pattern formation step S9, an electrolytic plating step S10, a resist pattern removal step S11, and an etching step S12.

[0053] In the preparation step S1, a first base film 10 is prepared. A first layer 22a is formed on a first main surface 10a and a second main surface 10b of the first base film 10 prepared in the preparation step S1. A through hole 10c is formed in the first base film 10 prepared in the preparation step S1 and its first layer 22a before the conductive treatment step S2 is performed. The through hole 10c is formed by, for example, irradiating with a laser.

[0054] 7 is a cross-sectional view illustrating the conductive treatment step S2. As shown in FIG. 7, in the conductive treatment step S2, a second layer 22b is formed on the first layer 22a and on the inner wall surface of the through hole 10c. The second layer 22b is formed by, for example, electroless plating.

[0055] 8 is a cross-sectional view illustrating the resist pattern forming step S3. As shown in FIG. 8, in the resist pattern forming step S3, a resist pattern 50 is formed on the conductive layer 22 (second layer 22b). In the resist pattern forming step S3, first, a dry film resist is applied to the conductive layer 22. Second, the dry film resist applied to the conductive layer 22 is exposed and developed. This forms a resist pattern 50 having openings 50a. The conductive layer 22 is exposed from the openings 50a.

[0056] 9 is a cross-sectional view illustrating the electrolytic plating step S4. As shown in FIG. 9, in the electrolytic plating step S4, an electrolytic plated layer 23 is formed on the conductive layer 22 exposed from the opening 50 a. The electrolytic plated layer 23 is formed by electrolytic plating.

[0057] Fig. 10 is a cross-sectional view illustrating the resist pattern removal step S5. As shown in Fig. 10, in the resist pattern removal step S5, the resist pattern 50 is removed from above the conductive layer 22. Fig. 11 is a cross-sectional view illustrating the etching step S6. As shown in Fig. 11, in the etching step S6, the conductive layer 22 that was underneath the resist pattern 50 is removed by etching. As a result, the first wiring 20 and the second wiring 21 are formed.

[0058] FIG. 12 is a cross-sectional view illustrating the heat-pressing step S7. As shown in FIG. 12, the heat-pressing step S7 forms a first resin layer 30 and a second resin layer 31. In the heat-pressing step S7, first, the second base film 30d is attached to the first main surface 10a by the first adhesive layer 30c, and the third base film 31d is attached to the second main surface 10b by the second adhesive layer 31c. At this stage, the first adhesive layer 30c and the second adhesive layer 31c are uncured. The first adhesive layer 30c and the second adhesive layer 31c are preferably made of a material with a large flow rate to easily fill the gaps between adjacent first wiring 20 and adjacent second wiring 21. A first layer 42a is disposed on the second base film 30d and the third base film 31d.

[0059] Second, the first base film 10, the first wiring 20, the second wiring 21, the first adhesive layer 30c, the second adhesive layer 31c, the second base film 30d, and the third base film 31d are sandwiched between the first plate member 60 and the second plate member 61, and then heated and pressurized. The first plate member 60 and the second plate member 61 are, for example, stainless steel plates. At this time, only the release layer 63 is disposed between the first plate member 60 and the second base film 30d and between the second plate member 61 and the third base film 31d. In other words, no press cushion layer (the layer of resin material that softens when heated) is disposed between the first plate member 60 and the second base film 30d and between the second plate member 61 and the third base film 31d. This hardens the first adhesive layer 30c and the second adhesive layer 31c, forming a first resin layer 30 on the first main surface 10a to cover the first wiring 20 and a second resin layer 31 on the second main surface 10b to cover the second wiring 21.

[0060] When the second wiring 21 is not formed, the first base film 10, the first wiring 20, the first adhesive layer 30c and the second base film 30d are sandwiched between the first plate member 60 and the second plate member 61, and only the release layer 63 is arranged between the first plate member 60 and the second base film 30d and between the second plate member 61 and the second main surface 10b.

[0061] Although not shown, after the heat pressing step S7 and before the conductive treatment step S8, through holes 30e are formed in the first resin layer 30 and the first layer 42a disposed thereon, and through holes 31e are formed in the second resin layer 31 and the first layer 42a disposed thereon. The through holes 30e and 31e are formed by, for example, irradiating with a laser.

[0062] 13 is a cross-sectional view illustrating the conductive treatment step S8. As shown in FIG. 13, in the conductive treatment step S8, a second layer 42b is formed on the first layer 42a. Although not shown, the second layer 42b is also formed on the inner wall surface of the through hole 30e, on the other end of the first wiring 20 exposed from the through hole 30e, and on the inner wall surface of the through hole 31e and on the other end of the second wiring 21 exposed from the through hole 31e. The second layer 42b is formed by, for example, electroless plating.

[0063] 14 is a cross-sectional view illustrating the resist pattern forming step S9. As shown in FIG. 14, in the resist pattern forming step S9, a resist pattern 51 is formed on the conductive layer 42 (second layer 42b). In the resist pattern forming step S9, first, a dry film resist is applied to the conductive layer 42. Second, the dry film resist applied to the conductive layer 42 is exposed and developed. The exposure at this time is performed by, for example, projection exposure. As a result, a resist pattern 51 having openings 51a is formed. The conductive layer 42 is exposed from the openings 51a.

[0064] 15 is a cross-sectional view illustrating the electrolytic plating step S10. As shown in FIG. 15, in the electrolytic plating step S10, an electrolytic plated layer 43 is formed on the conductive layer 42 exposed from the opening 51 a. The electrolytic plated layer 43 is formed by electrolytic plating.

[0065] 16 is a cross-sectional view illustrating the resist pattern removal step S11. As shown in FIG. 16, in the resist pattern removal step S11, the resist pattern 51 is removed from above the conductive layer 42. In the etching step S12, the conductive layer 42 that was underneath the resist pattern 51 is removed by etching. This forms the third wiring 40 and the fourth wiring 41. In this way, the coil device 100 having the structure shown in FIGS. 1 to 5 is formed.

[0066] (Effects of the Coil Device 100) The effects of the coil device 100 will be described below.

[0067] In the coil device 100, a plurality of coil portions are stacked in three or more layers (four layers in the example shown in FIGS. 1 to 6), thereby improving the coil characteristics (inductance).

[0068] In the heat pressing process S7, the portion of the first resin layer 30 (second resin layer 31) covering the first wiring 20 (second wiring 21) is more easily deformed than the portion of the first resin layer 30 (second resin layer 31) that does not cover the first wiring 20 (second wiring 21). Therefore, when a press cushion layer is interposed between the first plate member 60 and the second base film 30d and between the second plate member 61 and the third base film 31d, the portion of the first resin layer 30 (second resin layer 31) covering the first wiring 20 (second wiring 21) deforms before the portion of the first resin layer 30 (second resin layer 31) that does not cover the first wiring 20 (second wiring 21), and the softened press cushion layer penetrates between the portion of the first resin layer 30 (second resin layer 31) covering the first wiring 20 (second wiring 21) and the first plate member 60 (second plate member 61), making it difficult for force to be applied from the first plate member 60 (second plate member 61) to the first resin layer 30 (second resin layer 31) in a direction parallel to the pressure direction.

[0069] As a result, when a press cushion layer is interposed between the first plate member 60 and the second base film 30d and between the second plate member 61 and the third base film 31d, the portion of the first resin layer 30 (second resin layer 31) covering the first wiring 20 (second wiring 21) is likely to recess toward the first base film 10, and the minimum value of the distance DIS becomes smaller (the difference between the maximum value of the distance DIS and the minimum value of the distance DIS becomes larger).

[0070] When the difference between the maximum value of the distance DIS and the minimum value of the distance DIS becomes large, the thickness of the dry film resist applied to form the resist pattern 51 becomes partially smaller. As a result, the thickness of the resist pattern 51 in the portion where the opening 51a is formed becomes smaller than the height H1 (height H2), and adjacent portions of the third wiring 40 (fourth wiring 41) are connected on the resist pattern 51, resulting in defective formation of the third wiring 40 (fourth wiring 41). Furthermore, even if adjacent portions of the third wiring 40 (fourth wiring 41) are not connected on the resist pattern 51, the third wiring 40 (fourth wiring 41) may be formed on the portion of the resist pattern 51 around the opening 51a, making it impossible to peel off the resist pattern 51.

[0071] If the distance SP1 (distance SP2) is small, projection exposure must be used for the exposure when forming the resist pattern 51 in order to increase the exposure resolution. If there is a large difference between the maximum value of the distance DIS and the minimum value of the distance DIS and if there is variation in the thickness of the dry film resist applied to form the resist pattern 51, the focus will be shifted when performing projection exposure. This kind of focus shift also causes the third wiring 40 (fourth wiring 41) to be unable to be formed appropriately.

[0072] On the other hand, in the manufacturing process of the coil device 100, in the heat pressing step S7, no press cushion layer is interposed between the first plate member 60 and the second base film 30d and between the second plate member 61 and the third base film 31d. Therefore, in the manufacturing process of the coil device 100, a force is likely to be applied from the first plate member 60 (second plate member 61) to the first resin layer 30 (second resin layer 31) parallel to the pressure direction. As a result, in the coil device 100, the difference between the maximum value of the distance DIS and the minimum value of the distance DIS is small. Therefore, in the coil device 100, the thickness of the dry film resist applied to form the resist pattern 51 is less likely to vary, and the third wiring 40 (fourth wiring 41) can be appropriately formed.

[0073] The embodiments disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims, not by the above-described embodiments, and is intended to include all modifications within the meaning and scope of the claims.

[0074] 10 First base film, 10a First main surface, 10b Second main surface, 10c Through hole, 20 First wiring, 20a First coil portion, 21 Second wiring, 21a Second coil portion, 22 Conductive layer, 22a First layer, 22b Second layer, 23 Electrolytic plating layer, 30 First resin layer, 30a First surface, 30b Second surface, 30c First adhesive layer, 30d Second base film, 30e Through hole, 31 Second resin layer, 31a Third surface, 31b Fourth surface, 31c Second adhesive layer, 31d Third base film, 31e Through hole, 40 Third wiring, 40a Third coil portion, 41 Fourth wiring, 41a Fourth coil portion, 42 Conductive layer, 42a First layer, 42b Second layer, 43 Electrolytic plating layer, 50 Resist pattern, 51 Resist pattern, 50a, 51a opening, 60 first plate member, 61 second plate member, 63 release layer, DIS distance, S1 preparation step, S2 conductive treatment step, S3 resist pattern formation step, S4 electrolytic plating step, S5 resist pattern removal step, S6 etching step, S7 heat pressing step, S8 conductive treatment step, S9 resist pattern formation step, S10 electrolytic plating step, S11 resist pattern removal step, S12 etching step, H1, H2 height, SP1, SP2 spacing.

Claims

1. A coil device comprising: a first base film having a first main surface and a second main surface which is the opposite surface of the first main surface; a first wiring disposed on the first main surface and having a first coil portion wound in a spiral shape in a plan view; and a first resin layer disposed on the first main surface so as to cover the first wiring, the first resin layer having a first surface facing the first main surface and a second surface which is the opposite surface of the first surface, wherein a value obtained by subtracting a minimum value of a distance between the second surface and the second main surface from a maximum value of the distance between the second surface and the second main surface is 10% or less of the maximum value of the distance between the second surface and the second main surface.

2. The coil device according to claim 1, wherein a maximum value of a distance between the second surface and the second main surface is 65 μm or more.

3. A coil device comprising: a first base film having a first main surface and a second main surface which is the opposite surface of the first main surface; a first wiring disposed on the first main surface and having a first coil portion wound in a spiral shape in a plan view; a second wiring disposed on the second main surface and having a second coil portion wound in a spiral shape in a plan view; a first resin layer disposed on the first main surface so as to cover the first wiring; and a second resin layer disposed on the second main surface so as to cover the second wiring, the first resin layer having a first surface facing the first main surface and a second surface which is the opposite surface of the first surface, the second resin layer having a third surface facing the second main surface and a fourth surface which is the opposite surface of the third surface, wherein a value obtained by subtracting a minimum value of a distance between the second surface and the fourth surface from a maximum value of the distance between the second surface and the fourth surface is 20% or less of the maximum value of the distance between the second surface and the fourth surface.

4. The coil device according to claim 3, wherein a maximum value of a distance between the second surface and the fourth surface is 125 μm or more.

5. The coil device according to claim 1 or 2, wherein an area of a portion of the first main surface on which the first wiring is disposed is 90% or less of the area of the first main surface.

6. The coil device according to claim 3 or 4, wherein an area of a portion of the first main surface on which the first wiring is disposed is 90% or less of the area of the first main surface, and an area of a portion of the second main surface on which the second wiring is disposed is 90% or less of the area of the second main surface.

7. The coil device according to any one of claims 1 to 6, further comprising a third wiring disposed on the second surface, wherein the third wiring has a conductive layer disposed on the second surface and an electrolytic plating layer disposed on the conductive layer.

8. The coil device according to claim 7, wherein the height of the third wiring is 45 μm or more.

9. The coil device according to claim 7 or 8, wherein the interval between adjacent third wirings is 15 μm or less.

10. A method for manufacturing a coil device, comprising: preparing a first base film having a first main surface and a second main surface which is the opposite surface of the first main surface; forming a first wiring having a first coil portion wound in a spiral shape in a plan view on the first main surface; disposing a first resin layer on the first main surface so as to cover the first wiring; and sandwiching the first base film, the first wiring, and the first resin layer between a first plate member and a second plate member and performing a hot press, wherein only a release layer is disposed between the first plate member and the first resin layer and between the second plate member and the second main surface.

11. A method for manufacturing a coil device, comprising: preparing a first base film having a first main surface and a second main surface which is the opposite surface of the first main surface; forming a first wiring having a first coil portion wound in a spiral shape in a plan view and a second wiring having a second coil portion wound in a spiral shape in a plan view on the first main surface and the second main surface, respectively; disposing a first resin layer on the first main surface so as to cover the first wiring and disposing a second resin layer on the second main surface so as to cover the second wiring; and sandwiching the first base film, the first wiring, the second wiring, the first resin layer, and the second resin layer between a first plate member and a second plate member and performing a hot press, wherein only a release layer is disposed between the first plate member and the first resin layer and between the second plate member and the second resin layer.

12. The first resin layer has a first surface facing the first main surface and a second surface opposite to the first surface. A conductive layer is disposed on the second surface. A step of forming a resist pattern having an opening for exposing the conductive layer by attaching a dry film resist on the conductive layer and exposing and developing the dry film resist; A step of forming an electrolytic plating layer by electrolytic plating on a portion of the conductive layer exposed from the opening; A step of removing the resist pattern; The method of manufacturing a coil device according to claim 10 or claim 11, further comprising a step of removing a portion of the conductive layer that was under the resist pattern by etching.

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