Coil device and actuator

Abstract

This coil device includes: a first insulating layer having a first main surface and a second main surface opposite the first main surface; first wiring disposed above the first main surface and having a first coil spirally wound in plan view; second wiring disposed above the second main surface and having a second coil spirally wound in plan view; a first adhesive layer disposed above the first main surface so as to cover the first wiring; a second insulating layer disposed above the first adhesive layer, having a third main surface opposing the first adhesive layer, and having a fourth main surface which is a surface opposite the third main surface; and a third wiring disposed above the fourth main surface and having a third coil spirally wound in plan view. The first coil, the second coil, and the third coil are disposed so as to mutually overlap in plan view. The distance between the fourth main surface and the upper surface of the first wiring in the first coil is 50 μm or less.

Description

Coil device and actuator

[0001] The present disclosure relates to a coil device and an actuator. This application claims priority to Japanese Patent Application No. 2024-000245, filed on January 4, 2024. The entire contents of the Japanese patent application are incorporated herein by reference.

[0002] 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 first base film, first and second wiring, and first and second insulating layers.

[0003] The first base film has a first main surface and a second main surface. The first main surface and the second main surface are end surfaces in the thickness direction of the base film. The second main surface is the surface opposite to the first main surface. The first wiring is arranged on the first main surface and has a first coil portion that is spirally wound in a planar view. The second wiring is arranged on the second main surface and has a second coil portion that is spirally wound in a planar view. The first coil portion and the second coil portion are arranged to overlap each other in a planar view.

[0004] The first insulating layer is disposed on the first main surface so as to cover the first wiring, and the second insulating layer is disposed on the second main surface so as to cover the second wiring.

[0005] Japanese Patent Application Laid-Open No. 2021-174794

[0006] The coil device of the present disclosure includes a first insulating layer 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 that is spirally wound in a plan view, a second wiring arranged on the second main surface and having a second coil portion that is spirally wound in a plan view, a first adhesive layer arranged on the first main surface so as to cover the first wiring, a second insulating layer arranged on the first adhesive layer and having a third main surface facing the first adhesive layer and a fourth main surface opposite the third main surface, and a third wiring arranged on the fourth main surface and having a third coil portion that is spirally wound in a plan view. The first coil portion, the second coil portion, and the third coil portion are arranged so as to overlap one another in a plan view. The distance between the top surface of the first wiring in the first coil portion and the fourth main surface is 50 μm or less.

[0007] FIG. 1 is a cross-sectional view of the coil device 100. FIG. 2 is a plan view of the printed wiring board 10. FIG. 3 is a plan view of the printed wiring board 10 viewed from the opposite direction to FIG. 2. FIG. 4 is a plan view of the printed wiring board 30. FIG. 5 is a plan view of the printed wiring board 50. FIG. 6 is a cross-sectional view of the actuator 200. FIG. 7 is a manufacturing process diagram of the coil device 100. FIG. 8 is a cross-sectional view illustrating the preparation step S1. FIG. 9 is a cross-sectional view illustrating the electroless plating step S21. FIG. 10 is a cross-sectional view illustrating the resist pattern formation step S22. FIG. 11 is a cross-sectional view illustrating the electrolytic plating step S23. FIG. 12 is a cross-sectional view illustrating the etching step S24. FIG. 13 is a cross-sectional view of the second insulating layer 31 (third insulating layer 51) prepared in the first attachment step S3. FIG. 14 is a cross-sectional view illustrating the first attachment step S3. FIG. 15 is a cross-sectional view illustrating the second wiring formation step S4. FIG. 16 is a cross-sectional view illustrating the second attachment step S5. Fig. 17 is a cross-sectional view illustrating the third wiring forming step S6 Fig. 18 is a cross-sectional view of a coil device 100 according to a modified example.

[0008] [Problem to be Solved by the Present Disclosure] The coil device described in Patent Document 1 generates a thrust force on a magnet arranged opposite the first coil portion by passing a current through the first coil portion and the second coil portion. To improve this thrust force, for example, it is conceivable to arrange another coil portion on the first insulating layer. More specifically, it is conceivable to arrange a second base film on the first insulating layer and arrange wiring having a third coil portion wound in a spiral shape on the second base film.

[0009] However, such a configuration leaves room for improvement in thrust. The present disclosure provides a coil device with improved thrust.

[0010] Effect of the Present Disclosure According to the coil device of the present disclosure, it is possible to improve thrust.

[0011] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described.

[0012] (1) A coil device according to an embodiment of the present disclosure includes a first insulating layer 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 spirally wound in a plan view; a second wiring disposed on the second main surface and having a second coil portion spirally wound in a plan view; a first adhesive layer disposed on the first main surface so as to cover the first wiring; a second insulating layer disposed on the first adhesive layer and having a third main surface facing the first adhesive layer and a fourth main surface opposite the third main surface; and a third wiring disposed on the fourth main surface and having a third coil portion spirally wound in a plan view. The first coil portion, the second coil portion, and the third coil portion are arranged to overlap one another in a plan view. The distance between the top surface of the first wiring in the first coil portion and the fourth main surface is 50 μm or less. The coil device described in (1) above can improve thrust.

[0013] (2) In the coil device of (1), the thickness of the second insulating layer may be smaller than the thickness of the first insulating layer. According to the coil device of (2), it is possible to further improve the thrust.

[0014] (3) In the coil device of (1) or (2), the thickness of the second insulating layer may be 0.5 times or less the thickness of the first insulating layer. The coil device of (3) can further improve thrust.

[0015] (4) In the coil device according to any one of (1) to (3), the thickness of the second insulating layer may be 0.9 times or less the distance between the top surface of the first wiring in the first coil portion and the fourth principal surface. The coil device according to (4) can further improve thrust.

[0016] (5) In the coil device according to any one of (1) to (4), the thickness of the second insulating layer may be 0.75 times or less the distance between the top surface of the first wiring in the first coil portion and the fourth principal surface. The coil device according to (5) can further improve thrust.

[0017] (6) In the coil device according to any one of (1) to (5), the thickness of the second insulating layer may be 2.0 times or less the distance between two adjacent portions of the first wiring in the first coil portion. The printed wiring board according to (6) can further improve thrust.

[0018] (7) The coil device according to (1) to (6) above may further include: a second adhesive layer disposed on the second principal surface so as to cover the second wiring; a third insulating layer disposed on the second adhesive layer and having a fifth principal surface facing the second adhesive layer and a sixth principal surface opposite the fifth principal surface; and a fourth wiring disposed on the sixth principal surface and having a fourth coil portion wound in a spiral shape in a planar view. The first coil portion, the second coil portion, the third coil portion, and the fourth coil portion may be disposed so as to overlap one another in a planar view. The distance between the upper surface of the second wiring in the second coil portion and the sixth principal surface may be 50 μm or less. The coil device according to (7) above can further improve thrust while reducing warpage.

[0019] (8) In the coil device of (7), the thickness of the third insulating layer may be smaller than the thickness of the first insulating layer. According to the coil device of (8), it is possible to further improve the thrust.

[0020] (9) In the coil device of (7) or (8), the thickness of the third insulating layer may be 0.5 times or less the thickness of the first insulating layer. The coil device of (8) can further improve thrust.

[0021] (10) In the coil device according to any one of (7) to (9), the thickness of the third insulating layer may be 0.9 times or less the distance between the top surface of the second wiring in the second coil portion and the sixth principal surface. The coil device according to (10) can further improve thrust.

[0022] (11) In the coil device according to any one of (7) to (10), the thickness of the third insulating layer may be 0.75 times or less the distance between the top surface of the second wiring in the second coil portion and the sixth principal surface. The coil device according to (11) can further improve thrust.

[0023] (12) In the coil device according to any one of (7) to (11) above, the thickness of the third insulating layer may be 2.0 times or less the distance between two adjacent portions of the second wiring in the second coil section. The printed wiring board according to (12) above can further improve thrust.

[0024] (13) An actuator according to an embodiment includes the coil device according to any one of (1) to (13) above and a magnet. The magnet is disposed so as to face the third coil portion. The actuator according to (13) above can improve thrust.

[0025] (14) A coil device according to another embodiment of the present disclosure includes: a first insulating layer having a first main surface; a first wiring having a first coil portion disposed on the first main surface and spirally wound in a plan view; a first adhesive layer disposed on the first main surface so as to cover the first wiring; a second insulating layer disposed on the first adhesive layer and having a second main surface facing the first adhesive layer and a third main surface opposite the second main surface; a second wiring having a second coil portion disposed on the third main surface and spirally wound in a plan view; a second adhesive layer disposed on the third main surface so as to cover the second wiring; a third insulating layer disposed on the second adhesive layer and having a fourth main surface facing the second adhesive layer and a fifth main surface opposite the fourth main surface; and a third wiring having a third coil portion disposed on the fifth main surface and spirally wound in a plan view. The first coil portion, the second coil portion, and the third coil portion are disposed so as to overlap one another in a plan view. The distance between the top surface of the first wiring in the first coil portion and the third principal surface is 50 μm or less. According to the coil device of (14) above, it is possible to improve thrust.

[0026] [Details of the embodiment of the present disclosure] Next, 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 a coil device 100.

[0027] (Configuration of Coil Device 100) The configuration of the coil device 100 will be described below.

[0028] FIG. 1 is a cross-sectional view of a coil device 100. FIG. 2 is a plan view of a printed wiring board 10. FIG. 3 is a plan view of the printed wiring board 10 viewed from the opposite direction to that of FIG. 2. FIG. 4 is a plan view of a printed wiring board 30. FIG. 5 is a plan view of a printed wiring board 50. As shown in FIGS. 1 to 5, the coil device 100 has a printed wiring board 10, a first adhesive layer 20, a printed wiring board 30, a second adhesive layer 40, and a printed wiring board 50.

[0029] The printed wiring board 10 has a first insulating layer 11, first wiring 12, and second wiring 13. The first insulating layer 11 has a first main surface 11a and a second main surface 11b. The first main surface 11a and the second main surface 11b are end surfaces of the first insulating layer 11 in the thickness direction. The second main surface 11b is the surface opposite to the first main surface 11a. The first insulating layer 11 is made of a flexible, electrically insulating material. The first insulating layer 11 is made of, for example, polyimide. A through hole 11c is formed in the first insulating layer 11. The through hole 11c penetrates the first insulating layer 11 in the thickness direction. The thickness of the first insulating layer 11 is defined as thickness T1.

[0030] The first wiring 12 is disposed on the first main surface 11 a. The first wiring 12 has a first coil portion 12 a. The first coil portion 12 a is a portion of the first wiring 12 that is wound in a spiral shape in a plan view.

[0031] The aspect ratio of the first wiring 12 in the first coil portion 12a is defined as the first aspect ratio. The width of the first wiring 12 in the first coil portion 12a is defined as width W1, and the height of the first wiring 12 in the first coil portion 12a is defined as height H1. The first aspect ratio is the value obtained by dividing the height H1 by the width W1. The first aspect ratio is, for example, 1 to 5. The width W1 is, for example, 20 μm to 60 μm. The height H1 is, for example, 20 μm to 100 μm. The spacing between two adjacent portions of the first wiring 12 in the first coil portion 12a is defined as spacing SP1. The spacing SP1 is, for example, 2 μm to 15 μm.

[0032] The second wiring 13 is disposed on the second main surface 11b. The second wiring 13 has a second coil portion 13a. The second coil portion 13a is a portion of the second wiring 13 that is wound in a spiral shape in a plan view. The second coil portion 13a is disposed so as to overlap the first coil portion 12a in a plan view.

[0033] The aspect ratio of the second wiring 13 in the second coil portion 13a is defined as the second aspect ratio. The width of the second wiring 13 in the second coil portion 13a is defined as the width W2, and the height of the second wiring 13 in the second coil portion 13a is defined as the height H2. The second aspect ratio is the value obtained by dividing the height H2 by the width W2. The second aspect ratio is, for example, 1 to 5. The width W2 is, for example, 20 μm to 60 μm. The height H2 is, for example, 20 μm to 100 μm. The spacing between two adjacent portions of the second wiring 13 in the second coil portion 13a is defined as the spacing SP2. The spacing SP2 is, for example, 2 μm to 15 μm.

[0034] Each of the first wiring 12 and the second wiring 13 has, for example, a seed layer 14, an electroless plated layer 15, and an electrolytic plated layer 16. The seed layer 14 is disposed on the main surfaces (first main surface 11a, second main surface 11b) of the first insulating layer 11. The seed layer 14 is, for example, composed of only a metal layer. The seed layer 14 may be composed of a combination of a metal layer and a nickel (Ni)-chromium (Cr) alloy layer. When the seed layer 14 is composed of only a metal layer, the metal layer is, for example, an electrolytic copper foil. When the seed layer 14 is composed of a combination of a metal layer and a nickel-chromium alloy layer, the metal layer is, for example, a sputtered copper layer.

[0035] The electroless plated layer 15 is a layer formed by electroless plating. The electroless plated layer 15 is disposed on the seed layer 14. The electroless plated layer 15 is also disposed on the inner wall surface of the through hole 11c and on the side surface of the seed layer 14 that is continuous with the inner wall surface of the through hole 11c. The constituent material of the electroless plated layer 15 is copper (Cu), for example. The electrolytic plated layer 16 is a layer formed by electrolytic plating. The electrolytic plated layer 16 is disposed on the electroless plated layer 15. The constituent material of the electrolytic plated layer 16 is copper, for example. The first wiring 12 and the second wiring 13 are electrically connected to each other by the electroless plated layer 15 and the electrolytic plated layer 16 that are embedded in the through hole 11c.

[0036] The first adhesive layer 20 is disposed on the first main surface 11a so as to cover the first wiring 12. The constituent material of the first adhesive layer 20 is, for example, an epoxy adhesive. The printed wiring board 30 has a second insulating layer 31 and third wiring 32. The second insulating layer 31 is disposed on the first adhesive layer 20.

[0037] The second insulating layer 31 has a third main surface 31a and a fourth main surface 31b. The third main surface 31a and the fourth main surface 31b are end surfaces of the second insulating layer 31 in the thickness direction. The third main surface 31a faces the first adhesive layer 20, and the fourth main surface 31b is the surface opposite the third main surface 31a. The second insulating layer 31 is made of a flexible, electrically insulating material. For example, the second insulating layer 31 is made of polyimide.

[0038] The distance between the top surface of the first wiring 12 in the first coil portion 12a and the fourth main surface 31b is defined as distance DIS1. Distance DIS1 may be 50 μm or less, or may be 20 μm or less. The thickness of the second insulating layer 31 is defined as thickness T2. Thickness T2 may be smaller than thickness T1. Thickness T2 may be 1 time or less than thickness T1, 0.9 times or less than thickness T1, or 0.5 times or less than thickness T1. Thickness T1 may be 0.9 times or less than distance DIS1, or 0.75 times or less than distance DIS1. Thickness T2 may be 2.0 times or less than spacing SP1, or may be 1.0 times or less than spacing SP1.

[0039] The third wiring 32 is disposed on the fourth main surface 31b. Although not shown, the third wiring 32 is electrically connected to the first wiring 12. The third wiring 32 has a third coil portion 32a. The third coil portion 32a is a portion of the third wiring 32 that is wound in a spiral shape in a plan view. The third coil portion 32a is disposed so as to overlap the first coil portion 12a and the second coil portion 13a in a plan view.

[0040] The third wiring 32 includes, for example, a seed layer 33 , an electroless plated layer 34 , and an electrolytic plated layer 35 .

[0041] The seed layer 33 is disposed on the fourth main surface 31b. The seed layer 33 is, for example, composed of only a metal layer. The seed layer 33 may be composed of a combination of a metal layer and a nickel-chromium alloy layer. When the seed layer 33 is composed of only a metal layer, the metal layer is, for example, an electrolytic copper foil. When the seed layer 33 is composed of a combination of a metal layer and a nickel-chromium alloy layer, the metal layer is, for example, a sputtered copper layer.

[0042] The electroless plated layer 34 is a layer formed by electroless plating. The electroless plated layer 34 is disposed on the seed layer 33. The constituent material of the electroless plated layer 34 is, for example, copper. The electrolytic plated layer 35 is a layer formed by electrolytic plating. The electrolytic plated layer 35 is disposed on the electroless plated layer 34. The constituent material of the electrolytic plated layer 35 is, for example, copper.

[0043] The second adhesive layer 40 is disposed on the second main surface 11b so as to cover the second wiring 13. The constituent material of the second adhesive layer 40 is, for example, an epoxy adhesive. The printed wiring board 50 has a third insulating layer 51 and fourth wiring 52. The third insulating layer 51 is disposed on the second adhesive layer 40.

[0044] The third insulating layer 51 has a fifth main surface 51a and a sixth main surface 51b. The fifth main surface 51a and the sixth main surface 51b are end surfaces of the third insulating layer 51 in the thickness direction. The fifth main surface 51a faces the second adhesive layer 40, and the sixth main surface 51b is the surface opposite the fifth main surface 51a. The third insulating layer 51 is made of a flexible, electrically insulating material. The material of the third insulating layer 51 is, for example, polyimide.

[0045] The distance between the upper surface of the second wiring 13 in the second coil portion 13a and the sixth main surface 51b is defined as distance DIS2. Distance DIS2 may be 50 μm or less, or may be 20 μm or less. The thickness of the third insulating layer 51 is defined as thickness T3. Thickness T3 may be smaller than thickness T1. Thickness T3 may be 1 time or less than thickness T1, 0.9 times or less than thickness T1, or 0.5 times or less than thickness T1. Thickness T3 may be 0.9 times or less than distance DIS2, or 0.75 times or less than distance DIS2. Thickness T3 may be 2.0 times or less than spacing SP2, or may be 1.0 times or less than spacing SP2.

[0046] The fourth wiring 52 is disposed on the sixth main surface 51b. Although not shown, the fourth wiring 52 is electrically connected to the second wiring 13. The fourth wiring 52 has a fourth coil portion 52a. The fourth coil portion 52a is a portion of the fourth wiring 52 that is wound in a spiral shape in a plan view. The fourth coil portion 52a is disposed so as to overlap the first coil portion 12a, the second coil portion 13a, and the third coil portion 32a in a plan view.

[0047] The fourth wiring 52 includes, for example, a seed layer 53 , an electroless plated layer 54 , and an electrolytic plated layer 55 .

[0048] The seed layer 53 is disposed on the sixth main surface 51b. The seed layer 53 is, for example, composed of only a metal layer. The seed layer 53 may be composed of a combination of a metal layer and a nickel-chromium alloy layer. When the seed layer 53 is composed of only a metal layer, the metal layer is, for example, an electrolytic copper foil. When the seed layer 53 is composed of a combination of a metal layer and a nickel-chromium alloy layer, the metal layer is, for example, a sputtered copper layer.

[0049] Electroless plated layer 54 is a layer formed by electroless plating. Electroless plated layer 54 is disposed on seed layer 53. Electroless plated layer 54 is made of, for example, copper. Electrolytic plated layer 55 is a layer formed by electrolytic plating. Electrolytic plated layer 55 is disposed on electroless plated layer 54. Electrolytic plated layer 55 is made of, for example, copper.

[0050] The coil device 100 may further include a third adhesive layer 60 , a fourth adhesive layer 61 , a fourth printed wiring board 70 , and a fifth insulating layer 80 .

[0051] The third adhesive layer 60 is disposed on the fourth main surface 31b so as to cover the third wiring 32. The fourth adhesive layer 61 is disposed on the sixth main surface 51b so as to cover the fourth wiring 52. The third adhesive layer 60 and the fourth adhesive layer 61 are made of, for example, an epoxy adhesive. The fourth printed wiring board 70 has a fourth insulating layer 71 and fifth wiring 72. The fourth insulating layer 71 is disposed on the fourth adhesive layer 61.

[0052] The fourth insulating layer 71 has a seventh main surface 71a and an eighth main surface 71b. The seventh main surface 71a and the eighth main surface 71b are end surfaces of the fourth insulating layer 71 in the thickness direction. The seventh main surface 71a faces the fourth adhesive layer 61, and the eighth main surface 71b is the surface opposite to the seventh main surface 71a. The fourth insulating layer 71 is made of a flexible, electrically insulating material. The fourth insulating layer 71 is made of, for example, polyimide. A through hole 71c is formed in the fourth insulating layer 71 and the fourth adhesive layer 61. The fourth wiring 52 is partially exposed from the through hole 71c.

[0053] The fifth wiring 72 is disposed on the eighth main surface 71 b. The fifth wiring 72 has an external connection terminal 72 a. The fifth wiring 72 also has, for example, a seed layer 73, an electroless plating layer 74, and an electrolytic plating layer 75.

[0054] The seed layer 73 is disposed on the eighth main surface 71b. The seed layer 73 is, for example, composed of only a metal layer. The seed layer 73 may be composed of a combination of a metal layer and a nickel-chromium alloy layer. When the seed layer 73 is composed of only a metal layer, the metal layer is, for example, an electrolytic copper foil. When the seed layer 73 is composed of a combination of a metal layer and a nickel-chromium alloy layer, the metal layer is, for example, a sputtered copper layer.

[0055] The electroless plated layer 74 is a layer formed by electroless plating. The electroless plated layer 74 is disposed on the seed layer 73. The electroless plated layer 74 is also disposed on the inner wall surface of the through hole 71c, on the fifth wiring 72 exposed from the through hole 71c, and on the side surface of the seed layer 73 that is continuous with the inner wall surface of the through hole 71c. The electroless plated layer 74 is made of, for example, copper. The electrolytic plated layer 75 is a layer formed by electrolytic plating. The electrolytic plated layer 75 is disposed on the electroless plated layer 74. The electrolytic plated layer 75 is made of, for example, copper. The fourth wiring 52 and the fifth wiring 72 are electrically connected to each other by the electroless plated layer 74 and the electrolytic plated layer 75 that are embedded in the through hole 71c.

[0056] A solder resist 76 is disposed on the eighth main surface 71b so as to cover the fifth wiring 72. The solder resist 76 has openings 76a formed therein to expose the external connection terminals 72a.

[0057] The fifth insulating layer 80 is disposed on the third adhesive layer 60. The fifth insulating layer 80 has a ninth main surface 80a and a tenth main surface 80b. The ninth main surface 80a and the tenth main surface 80b are end surfaces of the fifth insulating layer 80 in the thickness direction. The ninth main surface 80a faces the third adhesive layer 60. The tenth main surface 80b is the surface opposite the ninth main surface 80a. The constituent material of the fifth insulating layer 80 is a flexible, electrically insulating material. The constituent material of the fifth insulating layer 80 is, for example, polyimide.

[0058] The distance between the top surface of the third wiring 32 in the third coil portion 32a and the tenth main surface 80b is defined as distance DIS3. Distance DIS3 may be 50 μm or less, or may be 20 μm or less. The thickness of the fifth insulating layer 80 is defined as thickness T4. Thickness T4 may be smaller than thickness T1. Thickness T4 may be 1 time or less than thickness T1, 0.9 times or less than thickness T1, or 0.5 times or less than thickness T1. Thickness T4 may be 0.9 times or less than distance DIS3, or 0.75 times or less than distance DIS3.

[0059] The distance between the top surface of the fourth wiring 52 in the fourth coil portion 52a and the eighth main surface 71b is defined as distance DIS4. Distance DIS4 may be 50 μm or less, or may be 20 μm or less. The thickness of the fourth insulating layer 71 is defined as thickness T5. Thickness T5 may be smaller than thickness T1. Thickness T5 may be 1 time or less than thickness T1, 0.9 times or less than thickness T1, or 0.5 times or less than thickness T1. Thickness T4 may be 0.9 times or less than distance DIS4, or 0.75 times or less than distance DIS4.

[0060] <Actuator Using Coil Device 100> An actuator using the coil device 100 is referred to as actuator 200. FIG. 6 is a cross-sectional view of the actuator 200. As shown in FIG. 6, the actuator 200 includes the coil device 100 and a magnet 110. The magnet 110 is disposed so as to face the third coil portion 32a. The magnet 110 is in direct or indirect contact with the fifth insulating layer 80. When power is supplied from the external connection terminal 72a, a current flows through the first coil portion 12a, the second coil portion 13a, the third coil portion 32a, and the fourth coil portion 52a. A magnetic flux generated based on this current generates a thrust force on the magnet 110.

[0061] Although the above describes an example in which the coil device 100 is combined with the magnet 110 to form an actuator, the coil device 100 may also be used as an inductor without being combined with a magnet. In this case, the coil device 100 can increase the magnetic flux density, thereby increasing the inductance.

[0062] <Modifications> In the above, an example has been described in which the coil device 100 has the printed wiring board 30 and the third adhesive layer 60, but the coil device 100 does not have to have the printed wiring board 30 and the third adhesive layer 60. In this case, the fifth insulating layer 80 is disposed on the first adhesive layer 20. Also in this case, the distance DIS3 is set to the distance between the top surface of the first wiring 12 in the first coil portion 12a and the tenth main surface 80b. In the above, an example has been described in which the number of coil portions stacked in the thickness direction is four, but the number of coil portions stacked in the thickness direction may be five, six, seven, or more.

[0063] (Method of Manufacturing Coil Device 100) A method of manufacturing the coil device 100 will be described below.

[0064] 7 is a manufacturing process diagram of the coil device 100. As shown in FIG. 7, the manufacturing method of the coil device 100 includes a preparation step S1, a first wiring forming step S2, a first attachment step S3, a second wiring forming step S4, a second attachment step S5, a third wiring forming step S6, and a solder resist forming step S7.

[0065] 8 is a cross-sectional view illustrating the preparation step S1. As shown in FIG. 8, in the preparation step S1, a first insulating layer 11 is prepared. At this point, seed layers 14 are disposed on the first main surface 11a and the second main surface 11b. Although not shown, after the first insulating layer 11 is prepared, through holes 11c are formed. The through holes 11c are formed, for example, by irradiating with laser light.

[0066] In the first wiring formation step S2, the first wiring 12 and the second wiring 13 are formed. The first wiring formation step S2 includes an electroless plating step S21, a resist pattern formation step S22, an electrolytic plating step S23, and an etching step S24.

[0067] 9 is a cross-sectional view illustrating the electroless plating step S21. As shown in Fig. 9, in the electroless plating step S21, electroless plating is performed to form an electroless plated layer 15 on the seed layer 14. In the electroless plating step S21, the electroless plating layer 15 is also formed on the inner wall surface of the through hole 11c and on the side surface of the seed layer 14 that is continuous with the inner wall surface of the through hole 11c.

[0068] 10 is a cross-sectional view illustrating the resist pattern forming step S22. As shown in FIG. 10, in the resist pattern forming step S22, a resist pattern 17 is formed on the electroless plated layer 15. The resist pattern 17 is formed, for example, by applying a dry film resist to the electroless plated layer 15 and then exposing and developing the applied dry film resist. The resist pattern 17 has openings 17a that partially expose the electroless plated layer 15.

[0069] 11 is a cross-sectional view illustrating the electrolytic plating step S23. As shown in FIG. 11, in the electrolytic plating step S23, electrolytic plating is performed to form an electrolytic plated layer 16 on the electroless plated layer 15 exposed from the opening 17a. After the electrolytic plated layer 16 is formed, the resist pattern 17 is removed.

[0070] 12 is a cross-sectional view illustrating the etching step S24. As shown in FIG. 12, in the etching step S24, the electroless plating layer 15 and the seed layer 14 that were located under the resist pattern 17 are removed by etching. In this manner, the first wiring 12 and the second wiring 13 are formed by, for example, a semi-additive method. In this manner, the printed wiring board 10 is formed.

[0071] Although not shown, an electrolytic plating step may be further performed after the etching step S24. In this electrolytic plating step, an electric current is passed through seed layer 14, electroless plated layer 15, and electrolytic plated layer 16 in a plating solution, thereby forming an electrolytic plated layer so as to cover seed layer 14, electroless plated layer 15, and electrolytic plated layer 16.

[0072] In the first attaching step S3, the second insulating layer 31 and the third insulating layer 51 are attached to the printed wiring board 10. In the first attaching step S3, the second insulating layer 31 and the third insulating layer 51 are first prepared. FIG. 13 is a cross-sectional view of the second insulating layer 31 (third insulating layer 51) prepared in the first attaching step S3. As shown in FIG. 13 , at this point, the second insulating layer 31 has a first adhesive layer 20 disposed on its third main surface 31 a, a seed layer 33 disposed on its fourth main surface 31 b, and a carrier film 36 disposed on the seed layer 33. Similarly, at this point, the third insulating layer 51 has a seed layer 53 disposed on its sixth main surface 51 b, a second adhesive layer 40 disposed on its fifth main surface 51 a, and a carrier film 56 disposed on the seed layer 53.

[0073] 14 is a cross-sectional view illustrating the first attaching step S3. As shown in FIG. 14, in the first attaching step S3, secondly, the second insulating layer 31 is adhered to the printed wiring board 10 by the first adhesive layer 20, and the third insulating layer 51 is adhered to the printed wiring board 10 by the second adhesive layer 40.

[0074] More specifically, first, the second insulating layer 31 is disposed on the first adhesive layer 20, and the third insulating layer 51 is disposed on the second adhesive layer 40. Next, the second insulating layer 31 is heated and pressed toward the printed wiring board 10, and the third insulating layer 51 is heated and pressed toward the printed wiring board 10. As a result, the first adhesive layer 20 is cured to bond the second insulating layer 31, and the second adhesive layer 40 is cured to bond the third insulating layer 51. The above pressure is applied by sandwiching the printed wiring board 10 and the second insulating layer 31 and third insulating layer 51 shown in FIG. 13 between a pair of metal plates. A cushioning material may be inserted between the metal plate and the carrier film 36 (carrier film 56). For example, only a release film may be inserted as the cushioning material; thermoplastic resin, which is typically inserted together with a release film, is not used. After the first attachment step S3, the carrier film 36 and the carrier film 56 are peeled off. The use of the carrier films 36 and 56 can suppress warping of the second insulating layer 31 and the third insulating layer 51 (ensuring the flatness of the second insulating layer 31 and the third insulating layer 51). Furthermore, not using a thermoplastic resin as the cushioning material (using only a release material as the cushioning material) can also suppress warping of the second insulating layer 31 and the third insulating layer 51.

[0075] 15 is a cross-sectional view illustrating the second wiring formation step S4. As shown in FIG. 15, in the second wiring formation step S4, the third wiring 32 is formed and the fourth wiring 52 is also formed. The second wiring formation step S4 is performed in the same manner as the first wiring formation step S2. That is, the third wiring 32 and the fourth wiring 52 are formed by, for example, a semi-additive method.

[0076] 16 is a cross-sectional view illustrating the second attaching step S5. As shown in FIG. 16, in the second attaching step S5, the fourth insulating layer 71 is attached by the fourth adhesive layer 61, and the fifth insulating layer 80 is attached by the third adhesive layer 60. The second attaching step S5 is performed in the same manner as the first attaching step S3.

[0077] At this point, a seed layer 73 is disposed on the eighth main surface 71b. Although not shown, after the second attaching step S5 is performed, a through hole 71c is formed in the fourth insulating layer 71 and the fourth adhesive layer 61. The through hole 71c is formed, for example, by irradiating with laser light.

[0078] 17 is a cross-sectional view illustrating the third wiring forming step S6. As shown in FIG. 17, in the third wiring forming step S6, a fifth wiring 72 is formed. The third wiring forming step S6 is performed in the same manner as the first wiring forming step S2. That is, the fifth wiring 72 is formed, for example, by a semi-additive method. In the solder resist forming step S7, a solder resist 76 is formed on the eighth main surface 71b so as to cover the fifth wiring 72. As a result of the above, the coil device 100 having the structure shown in FIGS. 1 to 5 is formed.

[0079] (Effects of the Coil Device 100) The effects of the coil device 100 will be described below.

[0080] The closer the first coil portion 12a and the third coil portion 32a are arranged, and the closer the second coil portion 13a and the fourth coil portion 52a are arranged, the greater the inductance of the coil of the coil device 100 composed of the first coil portion 12a, the second coil portion 13a, the third coil portion 32a, and the fourth coil portion 52a, and the greater the electromagnetic induction. In the coil device 100, since the distances DIS1 and DIS2 are 50 μm or less, the inductance of the coil of the coil device 100, and therefore the electromagnetic induction, are increased, and the thrust force on the magnet 110 is greater. In particular, because the first coil portion 12a is closer to the magnet 110 than the second coil portion 13a, reducing the distance DIS1 has a significant effect of increasing the thrust force on the magnet 110.

[0081] In the coil device 100, the thickness T2 (thickness T3) is reduced to reduce the distance DIS1 (distance DIS2). Reducing the thickness T2 (thickness T3) increases the likelihood of deformation of the second insulating layer 31 (third insulating layer 51) during the first attachment step S3. However, because the carrier film 36 (carrier film 56) is disposed on the seed layer 33 of the second insulating layer 31 (seed layer 53 of the third insulating layer 51) during the first attachment step S3, deformation of the second insulating layer 31 (third insulating layer 51) during the first attachment step S3 can be suppressed. In the first attachment step S3, attachment is performed while applying a force uniformly across the surface to be pressed in a plan view, thereby further suppressing deformation of the second insulating layer 31 (third insulating layer 51).

[0082] In the coil device 100, the printed wiring board 10 is sandwiched between the printed wiring boards 30 and 50, resulting in a nearly symmetrical structure with respect to the printed wiring board 10. Therefore, the coil device 100 can suppress warping while improving the thrust force by increasing the number of coil portions.

[0083] (Other Modifications) The coil device 100 may include at least a configuration in which the distance between the upper surface of a wiring and the main surface of an insulating layer, stacked on the wiring via an adhesive layer, opposite the adhesive layer is 50 μm or less. FIG. 18 is a cross-sectional view of a coil device 100 according to a modification. As shown in FIG. 18 , in the coil device 100, the printed wiring board 10 does not have to have the first wiring 12. The coil device 100 does not have to have the first adhesive layer 20, the printed wiring board 30, the third adhesive layer 60, and the fifth insulating layer 80. That is, the coil device 100 may have a structure in which single-sided printed wiring boards are stacked. In the example shown in FIG. 18 , three single-sided printed wiring boards are stacked, but the number of single-sided printed wiring boards may be two, four, or more.

[0084] (Example) As shown in Tables 1 and 2, Samples 1 to 12 were prepared. The distances DIS1, DIS2, and DIS3, the thicknesses T1, T2, and T3, the width W1, and the spacing SP1 were varied in Samples 1 to 12. Although not shown in Table 1, the width W2 and the spacing SP1 were the same as the width W1 and the spacing SP1 in Samples 1 to 12. Furthermore, blank spaces for the distances DIS1, DIS2, and DIS3 and their average values ​​in Table 1 indicate that the second insulating layer 31, the third insulating layer 51, and the fifth insulating layer 80 were so large that measurement was impossible. The presence or absence of a carrier film in the first attachment step S3 and the cushioning material in the first attachment step S3 were also varied in Samples 1 to 12. In Table 2, "A" in the cushioning material column indicates that a release film was used as the cushioning material, and "B" in the cushioning material column indicates that a release film and a thermoplastic resin were used as the cushioning material. A 50 μm thick polyethylene terephthalate was used as the release film for the cushioning material. The thickness of the thermoplastic resin for the cushioning material was 250 μm.

[0085]

[0086]

[0087] For Samples 1 to 12, the thrust generated by the current flowing through the first coil portion 12a to the fourth coil portion 52a was evaluated. The thrust for each sample was evaluated as a relative value when the thrust for Sample 1 was set to 1. For Samples 1 to 12, the short-circuit rate was measured. The short-circuit rate was calculated by checking using a microscope whether adjacent wiring portions were in contact, dividing the number of pieces that had short circuits by the total number inspected, and multiplying the result by 100. The thrust and short-circuit rate measured for Samples 1 to 12 are shown in Table 3.

[0088]

[0089] As shown in Tables 1 to 3, in each sample, the thrust was improved by reducing the distance DIS1 (distance DIS2, distance DIS3). In particular, sufficient thrust was ensured when the distance DIS1 (distance DIS2, distance DIS3) was 50 μm or less. Furthermore, a comparison of Sample 1 with Samples 2 to 5 shows that the thrust was improved as the thickness T2 (thickness T3) became smaller. Furthermore, a comparison of Sample 1 with Sample 6 shows that the thrust was improved by setting the thickness T2 to 0.75 times the distance DIS1 or less.

[0090] In Samples 8 to 10, a carrier film was not used in the first attachment step S3. As a result, in Samples 9 and 10, in which the second insulating layer 31 and the third insulating layer 51 were thin, the second insulating layer 31 and the third insulating layer 51 were significantly deflected in the first attachment step S3, resulting in an increased short-circuit rate and making manufacturing substantially difficult. Although manufacturing was possible for Sample 8, in which the second insulating layer 31 and the third insulating layer 51 were thick, the thickness of the second insulating layer 31 and the third insulating layer 51 made it impossible to obtain a distance DIS1 (distance DIS2) of 50 μm or less, resulting in insufficient thrust.

[0091] In Samples 11 and 12, not only a release film but also a thermoplastic resin was used as the cushioning material. As a result, it was difficult to apply uniform pressure in the first attachment step S3, and a distance DIS1 (distance DIS2) of 50 μm or less could not be obtained, resulting in insufficient thrust.

[0092] 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.

[0093] 100 coil device, 10 printed wiring board, 11 first insulating layer, 11a first main surface, 11b second main surface, 11c through hole, 12 first wiring, 12a first coil portion, 13 second wiring, 13a second coil portion, 14 seed layer, 15 electroless plating layer, 16 electrolytic plating layer, 17 resist pattern, 17a opening, 20 first adhesive layer, 30 printed wiring board, 31 second insulating layer, 31a third main surface, 31b fourth main surface, 32 third wiring, 32a third coil portion, 33 seed layer, 34 electroless plating layer, 35 electrolytic plating layer, 36 carrier film, 40 second adhesive layer, 50 printed wiring board, 51 third insulating layer, 51a fifth main surface, 51b sixth main surface, 52 fourth wiring, 52a fourth coil portion, 53 seed layer, 54 Electroless plated layer, 55 Electrolytic plated layer, 56 Carrier film, 60 Third adhesive layer, 61 Fourth adhesive layer, 70 Fourth printed wiring board, 71 Fourth insulating layer, 71a Seventh main surface, 71b Eighth main surface, 71c Through hole, 72 Fifth wiring, 72a External connection terminal, 73 Seed layer, 74 Electroless plated layer, 75 Electrolytic plated layer, 76 Solder resist, 76a Opening, 80 Fifth insulating layer, 80a Ninth main surface, 80b Tenth main surface, 110 Magnet, 200 Actuator, DIS1, DIS2, DIS3, DIS4 Distance, H1, H2 Height, S1 Preparation step, S2 First wiring forming step, S3 First bonding step, S4 Second wiring forming step, S5 Second bonding step, S6 Third wiring forming step, S7 Solder resist forming step, S21 Electroless plating step, S22 resist pattern forming step, S23 electrolytic plating step, S24 etching step, T1, T2, T3, T4, T5 thickness, W1, W2 width.

Claims

1. A coil device comprising: a first insulating layer 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 adhesive layer disposed on the first main surface so as to cover the first wiring; a second insulating layer disposed on the first adhesive layer and having a third main surface and a fourth main surface which is the opposite surface of the third main surface and facing the first adhesive layer; and a third wiring disposed on the fourth main surface and having a third coil portion wound in a spiral shape in a plan view, wherein the first coil portion, the second coil portion, and the third coil portion are arranged so as to overlap each other in a plan view, and a distance between an upper surface of the first wiring in the first coil portion and the fourth main surface is 50 μm or less.

2. The coil device according to claim 1, wherein a thickness of the second insulating layer is smaller than a thickness of the first insulating layer.

3. The coil device according to claim 1 or 2, wherein the thickness of the second insulating layer is 0.5 times or less of the thickness of the first insulating layer.

4. The coil device according to any one of claims 1 to 3, wherein the thickness of the second insulating layer is 0.9 times or less of the distance between an upper surface of the first wiring in the first coil portion and the fourth main surface.

5. The coil device according to any one of claims 1 to 4, wherein the thickness of the second insulating layer is 0.75 times or less of the distance between an upper surface of the first wiring in the first coil portion and the fourth main surface.

6. The coil device according to any one of claims 1 to 5, wherein the thickness of the second insulating layer is 2.0 times or less of the distance between two adjacent portions of the first wiring in the first coil portion.

7. A second adhesive layer disposed on the second main surface so as to cover the second wiring; a third insulating layer disposed on the second adhesive layer and having a fifth main surface facing the second adhesive layer and a sixth main surface opposite to the fifth main surface; and a fourth wiring disposed on the sixth main surface and having a fourth coil portion wound in a spiral shape in a plan view. The first coil portion, the second coil portion, the third coil portion, and the fourth coil portion are arranged so as to overlap each other in a plan view. The distance between the upper surface of the second wiring in the second coil portion and the sixth main surface is 50 μm or less. The coil device according to any one of claims 1 to 6.

8. The thickness of the third insulating layer is smaller than the thickness of the first insulating layer. The coil device according to claim 7.

9. The thickness of the third insulating layer is 0.5 times or less the thickness of the first insulating layer. The coil device according to claim 7 or claim 8.

10. The thickness of the third insulating layer is 0.9 times or less the distance between the upper surface of the second wiring in the second coil portion and the sixth main surface. The coil device according to any one of claims 7 to 9.

11. The thickness of the third insulating layer is 2.0 times or less the interval between two adjacent portions of the second wiring in the second coil portion. The coil device according to any one of claims 7 to 10.

12. The thickness of the third insulating layer is 0.75 times or less the distance between the upper surface of the second wiring in the second coil portion and the sixth main surface. The coil device according to any one of claims 7 to 11.

13. The coil device according to any one of claims 1 to 12, and a magnet. The magnet is arranged so as to face the third coil portion. An actuator.

14. A coil device comprising: a first insulating layer having a 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 first adhesive layer disposed on the first main surface so as to cover the first wiring; a second insulating layer disposed on the first adhesive layer and having a second main surface facing the first adhesive layer and a third main surface which is the opposite surface of the second main surface; a second wiring disposed on the third main surface and having a second coil portion wound in a spiral shape in a plan view; a second adhesive layer disposed on the third main surface so as to cover the second wiring; a third insulating layer disposed on the second adhesive layer and having a fourth main surface facing the second adhesive layer and a fifth main surface which is the opposite surface of the fourth main surface; and a third wiring disposed on the fifth main surface and having a third coil portion wound in a spiral shape in a plan view, wherein the first coil portion, the second coil portion, and the third coil portion are arranged so as to overlap each other in a plan view, and a distance between an upper surface of the first wiring in the first coil portion and the third main surface is 50 μm or less.

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