Coil Device

Abstract

This coil device comprises: a base film having a first major surface and a second major surface; a first coil wire disposed on the first major surface and having a portion wound in a spiral shape; a second coil wire disposed on the second major surface and having a portion wound in a spiral shape; a first protection layer disposed on the first major surface so as to cover the first coil wire; a second protection layer disposed on the second major surface so as to cover the second coil wire; and an electrically conductive portion. In the base film, a through-hole penetrating through the base film in a thickness direction is formed. The electrically conductive portion is embedded in the through-hole and connects the first coil wire and the second coil wire, whereby the first coil wire and the second coil wire are electrically connected.

Description

[Technical Field]

[0001] The present disclosure relates to a coil device. This application claims priority to Japanese Patent Application No. 2022-508, filed January 5, 2022, and Japanese Patent Application No. 2022-020719, filed February 14, 2022. The entire contents of the Japanese patent application are incorporated herein by reference. [Background technology]

[0002] For example, Japanese Patent Laid-Open No. 2016-9854 (Patent Document 1) describes a coil device that includes a base film, a first conductive pattern, a second conductive pattern, a plating layer, a first adhesive layer, a first cover film, a second adhesive layer, and a second cover film.

[0003] The base film has a first main surface and a second main surface opposite the first main surface. The base film has a through hole formed therein, penetrating the base film in the thickness direction. The first conductive pattern is spirally wound on the first main surface. The second conductive pattern is spirally wound on the second main surface. The first conductive pattern and the second conductive pattern are electrically connected by a plating layer formed on the inner wall surface of the through hole.

[0004] A first adhesive layer is disposed on the first main surface to cover the first conductive pattern. A first cover film is disposed on the first adhesive layer. A second adhesive layer is disposed on the second main surface to cover the second conductive pattern. A second cover film is disposed on the second adhesive layer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-9854 Summary of the Invention

[0006] The coil device of the present disclosure includes a base film having a first main surface and a second main surface, a first coil wiring disposed on the first main surface and having a spirally wound portion, a second coil wiring disposed on the second main surface and having a spirally wound portion, a first protective layer disposed on the first main surface so as to cover the first coil wiring, a second protective layer disposed on the second main surface so as to cover the second coil wiring, and a conductive portion. The base film has a through hole formed therethrough in the thickness direction. The conductive portion is embedded in the through hole and connects to the first coil wiring and the second coil wiring, thereby electrically connecting the first coil wiring and the second coil wiring. If the total mass of the first coil wiring, the second coil wiring, and the conductive portion is A and the total volume of the base film, the first coil wiring, the second coil wiring, the first protective layer, the second protective layer, and the conductive portion is B, the value of A / B is 2.0 g / cm. 3 That's all. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view of a coil device 100. As shown in FIG. [Figure 2] FIG. 2 is a plan view of the printed wiring board 10. As shown in FIG. [Figure 3] FIG. 3 is a bottom view of the printed wiring board 10. As shown in FIG. [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Figure 5] FIG. 5 is a process diagram showing a method for manufacturing printed wiring board 10. [Figure 6] FIG. 6 is a cross-sectional view illustrating the seed layer forming step S2. [Figure 7] FIG. 7 is a cross-sectional view illustrating the resist forming step S3. [Figure 8] FIG. 8 is a cross-sectional view illustrating the first electrolytic plating step S4. [Figure 9] FIG. 9 is a cross-sectional view illustrating the resist removing step S5. [Figure 10]FIG. 10 is a cross-sectional view illustrating the etching step S6. [Figure 11] FIG. 11 is a schematic diagram illustrating soldering of the coil device 100 to the substrate 60. As shown in FIG. [Figure 12] FIG. 12 is a cross-sectional view of a coil device 100 according to the first modification. [Figure 13] FIG. 13 is a cross-sectional view of a coil device 100 according to the second modification. [Figure 14] FIG. 14 is a cross-sectional view of a coil device 100 according to the third modification. DETAILED DESCRIPTION OF THE INVENTION

[0008] [Problem to be solved by this disclosure] However, the coil device described in Patent Document 1 has room for improvement in solderability, that is, in soldering to a substrate with high horizontality.

[0009] The present disclosure has been made in view of the above-described conventional techniques. More specifically, the present disclosure provides a coil device that can improve solderability.

[0010] [Effects of this disclosure] According to the coil device of the present disclosure, it is possible to improve solderability.

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

[0012] (1) A coil device according to one embodiment includes a base film having a first main surface and a second main surface, a first coil wiring disposed on the first main surface and having a spirally wound portion, a second coil wiring disposed on the second main surface and having a spirally wound portion, a first protective layer disposed on the first main surface so as to cover the first coil wiring, a second protective layer disposed on the second main surface so as to cover the second coil wiring, and a conductive portion. The base film has a through hole formed therethrough in the thickness direction. The conductive portion is embedded in the through hole and connected to the first coil wiring and the second coil wiring, thereby electrically connecting the first coil wiring and the second coil wiring. If the total mass of the first coil wiring, the second coil wiring, and the conductive portion is A and the total volume of the base film, the first coil wiring, the second coil wiring, the first protective layer, the second protective layer, and the conductive portion is B, the value of A / B is 2.0 g / cm. 3 That's all.

[0013] According to the coil device of (1) above, solderability can be improved. (2) The coil device of (1) above may further include an external connection terminal disposed on the first protective layer, and a solder resist disposed on the first protective layer so as to expose the external connection terminal.

[0014] (3) In the coil device of (1) or (2) above, the first coil wiring, the second coil wiring, and the conductive part may contain copper. The total volume of the base film, the first coil wiring, the second coil wiring, the first protective layer, the second protective layer, and the conductive part is C, and the volume of copper contained in the first coil wiring, the second coil wiring, and the conductive part is Sum of If D is the value of D / C×100, the value of D / C may be 10 percent or more and 70 percent or less.

[0015] (4) In the coil device according to (1) to (3) above, the first protective layer may be disposed on the first main surface so as to cover the first coil wiring and may have a first layer formed of an adhesive. The second protective layer may be disposed on the second main surface so as to cover the second coil wiring and may have a third layer formed of an adhesive.

[0016] (5) In the coil device of (4), the first protective layer may further include a second layer disposed on the first layer. The second protective layer may further include a fourth layer disposed on the third layer.

[0017] (6) In the coil device of (5) above, the second layer and the fourth layer may be made of polyimide.

[0018] (7) In the coil device according to (4) to (6) above, the first layer and the third layer may have a thickness of 2 μm or more and 100 μm or less.

[0019] (8) In the coil devices described in (1) to (7) above, the distance between two adjacent portions of the first coil wiring and the distance between two adjacent portions of the second coil wiring may be 2 μm or more and 20 μm or less. The thickness of the first coil wiring and the thickness of the second coil wiring may be 30 μm or more and 80 μm or less. The width of the first coil wiring and the width of the second coil wiring may be 10 μm or more and 100 μm or less.

[0020] (9) In the coil devices (1) to (8) above, the value obtained by dividing the thickness of the first coil wiring by the width of the first coil wiring and the value obtained by dividing the thickness of the second coil wiring by the width of the second coil wiring may be greater than or equal to 1.0 and less than or equal to 3.0.

[0021] (10) In the coil device according to (1) to (9) above, the height, width, and length of the coil device may be 100 μm or more and 500 μm or less, 2 mm or more and 10 mm or less, and 2 mm or more and 40 mm or less, respectively.

[0022] (11) A coil device according to another embodiment includes a base film having a first main surface and a second main surface, a first coil wiring disposed on the first main surface and having a spirally wound portion, a second coil wiring disposed on the second main surface and having a spirally wound portion, a first protective layer disposed on the first main surface so as to cover the first coil wiring, a second protective layer disposed on the second main surface so as to cover the second coil wiring, a conductive portion, and a dummy wiring electrically isolated from the first coil wiring and the second coil wiring and disposed on at least one of the first main surface and the second main surface. The base film has a through hole penetrating the base film along the thickness direction. The conductive portion is embedded in the through hole and connected to the first coil wiring and the second coil wiring, thereby electrically connecting the first coil wiring and the second coil wiring. The value obtained by dividing the total mass of the first coil wiring, the second coil wiring, the conductive part, and the dummy wiring by the total volume of the base film, the first coil wiring, the second coil wiring, the first protective layer, the second protective layer, the conductive part, and the dummy wiring is 2.0 g / cm 3 That's all.

[0023] According to the coil device of (11) above, the density can be adjusted by using dummy wiring.

[0024] [Details of the embodiments of the present disclosure] Next, details of embodiments 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.

[0025] (Configuration of coil device according to embodiment) The configuration of a coil device according to an embodiment (hereinafter referred to as "coil device 100") will be described below.

[0026] 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 bottom view of the printed wiring board 10. FIG. 3 shows the printed wiring board 10 as seen from the opposite side to that of FIG. 2. FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. 2. As shown in FIGS. 1, 2, 3, and 4, the coil device 100 has a printed wiring board 10, a first protective layer 20, a second protective layer 30, wiring 40, and a solder resist 50.

[0027] The printed wiring board 10 includes a base film 11 , a coil wiring 12 , and a conductive portion 15 .

[0028] The base film 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 base film 11 in the thickness direction. The second main surface 11b is the surface opposite to the first main surface 11a. The base film 11 is made of a flexible, electrically insulating material. More specifically, the base film 11 is made of, for example, polyimide.

[0029] A through hole 11c is formed in the base film 11. The through hole 11c penetrates the base film 11 in the thickness direction.

[0030] The coil wiring 12 is arranged on the main surface of the base film 11. The coil wiring 12 has first coil wiring 13 and second coil wiring 14. The first coil wiring 13 is arranged on the first main surface 11a. The first coil wiring 13 has a portion that is spirally wound when viewed from the first main surface 11a along the thickness direction of the base film 11. The second coil wiring 14 is arranged on the second main surface 11b. The second coil wiring 14 has a portion that is spirally wound when viewed from the second main surface 11b along the thickness direction of the base film 11.

[0031] Preferably, the area of ​​the portion of the first coil wiring 13 that is spirally wound when viewed from the first main surface 11a along the thickness direction of the base film 11 and the area of ​​the portion of the second coil wiring 14 that is spirally wound when viewed from the second main surface 11b along the thickness direction of the base film 11 are 10 cm or less. 2 More than 50cm 2 below These areas are the sum of the area of ​​the spirally wound portion and the area of ​​the land portion. The area of ​​the spirally wound portion and the area of ​​the land portion are calculated based on the values ​​obtained by scanning the coil device 100 using an X-ray CT to determine the dimensions and layer structure of the coil portion and conductive portion.

[0032] The distance between adjacent portions of the coil wiring 12 (first coil wiring 13, second coil wiring 14) is defined as distance L. The thickness of the coil wiring 12 (first coil wiring 13, second coil wiring 14) is defined as thickness T. The width of the coil wiring 12 (first coil wiring 13, second coil wiring 14) is defined as width W.

[0033] The distance L is preferably 2 μm or more and 20 μm or less. The thickness T is preferably 30 μm or more and 80 μm or less, and more preferably 40 μm or more and 60 μm or less. The width W is preferably 10 μm or more and 100 μm or less, and more preferably 15 μm or more and 30 μm or less. The value obtained by dividing the thickness T by the width W is preferably 1.0 or more and 3.0 or less, and more preferably 1.5 or more and 2.5 or less. The thickness T, width W, and distance L of the coil wiring 12 (first coil wiring 13, second coil wiring 14) are obtained by exposing the cross section of the coil wiring 12 using a cross-section processing device such as a microtome and averaging values ​​measured at any 10 points on the cross section.

[0034] The end of the first coil wiring 13 forms a land 13a. The end of the second coil wiring 14 forms a land 14a. The lands 13a and 14a overlap the through-hole 11c. The difference between the thickness T of the land 13a and the thickness T of the spirally wound portion of the first coil wiring 13, and the difference between the thickness T of the land 14a and the thickness T of the spirally wound portion of the second coil wiring 14, are preferably 8 μm or less. The difference between the thickness T of the land 13a and the thickness T of the spirally wound portion of the first coil wiring 13, and the difference between the thickness T of the land 14a and the thickness T of the spirally wound portion of the second coil wiring 14, may be 0 μm or more. The difference between the thickness T of the land 13a and the thickness T of the spirally wound portion of the first coil wiring 13 may be 1% or more of the thickness T of the spirally wound portion of the first coil wiring 13. The difference between the thickness T of the land 14a and the thickness T of the spirally wound portion of the second coil wiring 14 may be 1 percent or more of the thickness T of the spirally wound portion of the second coil wiring 14. The thickness T of the land 13a and the thickness T of the land 14a are the maximum thickness values ​​in cross sections of the land 13a and the land 14a exposed by a cross-section processing device such as a microtome. The thickness T of the first coil wiring 13 portion and the thickness T of the second coil wiring 14 portion are obtained by exposing the cross section of the coil wiring 12 (first coil wiring 13, second coil wiring 14) by a cross-section processing device such as a microtome and then averaging values ​​measured at any 10 points on the cross section.

[0035] The length of the first coil wiring 13 and the length of the second coil wiring 14 are preferably 150 mm or more and 1000 mm or less. The sum of the lengths of the first coil wiring 13 and the second coil wiring 14 is preferably 300 mm or more and 2000 mm or less.

[0036] The width W of the land 13a is larger than the width W of the spirally wound portion of the first coil wiring 13. The width W of the land 14a is larger than the width W of the spirally wound portion of the second coil wiring 14.

[0037] Coil wiring 12 (first coil wiring 13, second coil wiring 14) has a seed layer 12a, a first electrolytic plated layer 12b, and a second electrolytic plated layer 12c.

[0038] The seed layer 12a is disposed on the main surfaces (first main surface 11a and second main surface 11b) of the base film 11. The seed layer 12a has a first layer 12aa and a second layer 12ab. The first layer 12aa is disposed on the main surfaces (first main surface 11a and second main surface 11b) of the base film 11. The second layer 12ab is disposed on the first layer 12aa. The second layer 12ab is also disposed on the inner wall surfaces of the through holes 11c.

[0039] The first layer 12aa is, for example, a sputtered layer (a layer formed by sputtering). The first layer 12aa is, for example, formed of a nickel-chromium alloy. The second layer 12ab is, for example, an electroless plated layer (a layer formed by electroless plating). The second layer 12ab is, for example, formed of copper.

[0040] First electrolytic plated layer 12b is a layer formed by electrolytic plating. First electrolytic plated layer 12b is made of copper. First electrolytic plated layer 12b is disposed on seed layer 12a. First electrolytic plated layer 12b is also disposed on the inner wall surface of through hole 11c with second layer 12ab interposed therebetween.

[0041] Second electrolytic plated layer 12c is a layer formed by electrolytic plating. Second electrolytic plated layer 12c is formed of copper. Second electrolytic plated layer 12c covers seed layer 12a and first electrolytic plated layer 12b. More specifically, second electrolytic plated layer 12c is disposed on the side surfaces of seed layer 12a and on the side surfaces and top surface of first electrolytic plated layer 12b.

[0042] The second layer 12ab and the first electrolytic plated layer 12b disposed on the through hole 11c form a conductive portion 15. The conductive portion 15 electrically connects the first coil wiring 13 (land 13a) and the second coil wiring 14 (land 14a).

[0043] Fig. 5 is a process diagram showing a method for manufacturing printed wiring board 10. As shown in Fig. 5, the method for manufacturing printed wiring board 10 includes a preparation step S1, a seed layer formation step S2, a resist formation step S3, a first electrolytic plating step S4, a resist removal step S5, an etching step S6, and a second electrolytic plating step S7.

[0044] In the preparation step S1, a base film 11 is prepared. The base film 11 prepared in the preparation step S1 does not have coil wiring 12 formed thereon. Furthermore, the base film 11 prepared in the preparation step S1 does not have through holes 11c formed therein.

[0045] 6 is a cross-sectional view illustrating the seed layer forming step S2. As shown in FIG. 6, in the seed layer forming step S2, a seed layer 12a is formed. In the seed layer forming step S2, first, a first layer 12aa is formed by sputtering. In the seed layer forming step S2, second, a through hole 11c is formed. The through hole 11c is formed using a laser or a drill.

[0046] Thirdly, in the seed layer formation step S2, the second layer 12ab is formed by electroless plating. Because the through hole 11c is formed before the electroless plating is performed, the second layer 12ab is also formed on the inner wall surface of the through hole 11c.

[0047] 7 is a cross-sectional view illustrating the resist formation step S3. In the resist formation step S3, a resist 16 is formed. The resist 16 is formed by applying a photosensitive organic material onto the seed layer 12a and exposing and exposing the applied photosensitive organic material to light. The resist 16 is formed by applying a dry film resist onto the seed layer 12a and exposing the applied dry film resist to light. Film Resist The seed layer 12a is exposed from the openings in the resist 16.

[0048] 8 is a cross-sectional view illustrating the first electrolytic plating step S4. As shown in FIG. 8, in the first electrolytic plating step S4, a first electrolytic plated layer 12b is formed. In the first electrolytic plating step S4, a current is passed through the seed layer 12a in a plating solution, so that the first electrolytic plated layer 12b grows from the seed layer 12a exposed through the openings in the resist 16. At this time, the first electrolytic plated layer 12b also grows from the second layer 12ab on the through-hole 11c.

[0049] 9 is a cross-sectional view illustrating resist removal step S5. As shown in Fig. 9, in resist removal step S5, resist 16 is removed. After resist 16 is removed, seed layer 12a is exposed between adjacent first electrolytic plated layers 12b.

[0050] Fig. 10 is a cross-sectional view illustrating the etching step S6. As shown in Fig. 10, in the etching step S6, the seed layer 12a exposed between adjacent first electrolytic plated layers 12b is removed.

[0051] In the etching step S6, first, the second layer 12ab is etched. The etching of the second layer 12ab is performed by supplying an etching solution between adjacent first electroplated layers 12b. The etching solution is selected so that the etching rate is determined by the reaction between the reactive species in the etching solution and the etching target, rather than by the diffusion of reactive species in the etching solution to the vicinity of the etching target.

[0052] More specifically, the etching solution used has a dissolution reaction rate of 1.0 μm / min or less for the material (i.e., copper) constituting the second layer 12ab. Specific examples of the etching solution include an aqueous solution of sulfuric acid and hydrogen peroxide, and an aqueous solution of sodium peroxodisulfate. The dissolution reaction rate of the etching solution is measured based on the weight of copper lost after etching and the etching time.

[0053] Secondly, in the etching step S6, etching is performed on the first layer 12aa. When etching the first layer 12aa, the etching solution is switched. The new etching solution is one with a high selectivity to the material (i.e., nickel-chromium alloy) that constitutes the first layer 12aa. Therefore, after the etching solution is switched, etching of the first electroplated layer 12b is less likely to proceed.

[0054] In the second electrolytic plating step S7, a second electrolytic plated layer 12c is formed. In the second electrolytic plating step S7, a current is passed through the seed layer 12a and the first electrolytic plated layer 12b in the plating solution, so that the second electrolytic plated layer 12c grows to cover the seed layer 12a and the first electrolytic plated layer 12b. In this manner, the printed wiring board 10 is manufactured. Note that, for example, by appropriately adjusting the jetting speed and current density of the plating solution in the second electrolytic plating step S7, it is possible to change the difference between the thickness T of the land 13a and the thickness T of the spirally wound portion of the first coil wiring 13, and the difference between the thickness T of the land 14a and the thickness T of the spirally wound portion of the second coil wiring 14.

[0055] As shown in FIG. 1, the first protective layer 20 is disposed on the first main surface 11a so as to cover the first coil wiring 13. The first protective layer 20 has a first layer 21 and a second layer 22. The first layer 21 is disposed on the first main surface 11a so as to cover the first coil wiring 13. Although not shown, a through hole is formed in the first protective layer 20. The through hole penetrates the first protective layer 20 in the thickness direction, exposing the first coil wiring 13. Note that the first protective layer 20 does not necessarily have to have the second layer 22.

[0056] The second protective layer 30 is disposed on the second main surface 11b so as to cover the second coil wiring 14. The second protective layer 30 has a third layer 31 and a fourth layer 32. The third layer 31 is disposed on the second main surface 11b so as to cover the second coil wiring 14. The fourth layer 32 is disposed on the third layer 31. Note that the second protective layer 30 does not necessarily have to have the fourth layer 32.

[0057] The first layer 21 and the third layer 31 are formed of, for example, an adhesive. 。 The second layer 22 and the fourth layer 32 are made of, for example, polyimide.

[0058] The thickness of the first layer 21 and the thickness of the third layer 31 are defined as thickness T1 and thickness T2, respectively. Thickness T1 is the maximum value of the distance between the upper surface of the first coil wiring 13 and the upper surface of the first layer 21. Thickness T2 is the maximum value of the distance between the upper surface of the second coil wiring 14 and the upper surface of the third layer 31. Thickness T1 and thickness T2 are preferably 2 μm or more and 50 μm or less. Thickness T1 and thickness T2 are obtained by exposing a cross-section of the coil device 100 using a cross-section processing device such as a microtome and then averaging values ​​measured at any 10 points on the cross-section.

[0059] The wiring 40 is disposed on the first protective layer 20. The wiring 40 is formed of, for example, copper. Although not shown, the wiring 40 is electrically connected to the first coil wiring 13 by a conductive portion embedded in a through hole formed in the first protective layer 20. The wiring 40 has an external connection terminal 41. A plating layer 42 is disposed on the external connection terminal 41. The plating layer 42 is formed of, for example, gold. When a current flows through the coil wiring 12 via the external connection terminal 41, the coil wiring 12 generates a magnetic field.

[0060] The solder resist 50 is disposed on the first protective layer 20 so as to cover the wiring 40. Openings are formed in the solder resist 50. The external connection terminals 41 are exposed from the openings in the solder resist 50.

[0061] The total mass of the first coil wiring 13, the second coil wiring 14, and the conductive portion 15 is A, and the volume of the base film 11, the first coil wiring 13, the second coil wiring 14, the first protective layer 20, the second protective layer 30, and the conductive portion 15 is Sum of If B is used, the value of A / B is 2.0g / cm 3 The value of A / B is preferably 7.0 g / cm 3 The value of A / B is as follows: 、 2.2g / cm 3 More than 3.0g / cm 3 or more than 3.8g / cm 3 It is preferable that this is equal to or greater than this.

[0062] The density of copper, which is a material contained in the first coil wiring 13, the second coil wiring 14, and the conductive portion 15, is greater than the density of polyimide, which is a material constituting the base film 11, the second layer 22, and the fourth layer 32, and the density of the adhesive, which is a material constituting the first layer 21 and the third layer 31. Therefore, the greater the pattern density of the coil wiring 12 (the greater the width W and the smaller the distance L), and the greater the thickness T of the coil wiring 12, the greater the value obtained by dividing the total mass of the first coil wiring 13, the second coil wiring 14, and the conductive portion 15 by the total volume of the base film 11, the first coil wiring 13, the second coil wiring 14, the first protective layer 20, the second protective layer 30, and the conductive portion 15.

[0063] When calculating the value (A / B) obtained by dividing the total mass of the first coil wiring 13, the second coil wiring 14, and the conductive portion 15 by the total volume of the base film 11, the first coil wiring 13, the second coil wiring 14, the first protective layer 20, the second protective layer 30, and the conductive portion 15, first, the volume of each component of the coil device 100 measured using X-ray CT is calculated. That is, the layer configuration and dimensions of the base film 11, the first coil wiring 13, the second coil wiring 14, the first protective layer 20, the second protective layer 30, and the conductive portion 15 of the coil device 100 are measured to calculate the volume of each of these components, and then the total is calculated.

[0064] Second, the total mass of the first coil wiring 13, the second coil wiring 14 and the conductive portion 15 is calculated by multiplying the total volume of the first coil wiring 13, the second coil wiring 14 and the conductive portion 15 by the copper density, which is a known value.

[0065] As a result of the above, the total mass of the first coil wiring 13, the second coil wiring 14, and the conductive portion 15 and the total volume of the base film 11, the first coil wiring 13, the second coil wiring 14, the first protective layer 20, the second protective layer 30, and the conductive portion 15 are obtained, and the value (A / B value) obtained by dividing the total mass of the first coil wiring 13, the second coil wiring 14, and the conductive portion 15 by the total volume of the base film 11, the first coil wiring 13, the second coil wiring 14, the first protective layer 20, the second protective layer 30, and the conductive portion 15 can be calculated.

[0066] Furthermore, the total volume of the base film 11, the first coil wiring 13, the second coil wiring 14, the first protective layer 20, the second protective layer 30, and the conductive portion 15 is defined as C, and the volume of copper contained in the first coil wiring 13, the second coil wiring 14, and the conductive portion 15 is defined as Sum of When D is taken as D, the value of D / C×100 is preferably 10% or more and 70% or less.

[0067] The height, width and length of the coil device 100 are 100 μm or more and 500 μm or less, 2 mm or more and 10 mm or less and 2 mm or more and 40 mm or less, respectively.

[0068] FIG. 11 is a schematic diagram illustrating soldering of the coil device 100 to a substrate 60. As shown in FIG. 11, the coil device 100 is soldered to, for example, a substrate 60. The substrate 60 has terminals 61. The terminals 61 are on the main surface of the substrate 60. The substrate 60 is, for example, a rigid substrate, and the terminals 61 are made of, for example, copper. The coil device 100 is electrically connected to the substrate 60 by connecting the external connection terminals 41 (plating layer 42) and the terminals 61 with a connection layer 62 made of a solder alloy.

[0069] (Effects of the coil device according to the embodiment) The effects of the coil device 100 will be described below.

[0070] To improve the pattern density of the coil wiring, it is necessary to shorten the distance between adjacent coil wiring portions. Also, by increasing the thickness of the coil wiring, the electrical resistance of the coil wiring can be reduced.

[0071] Conventionally, etching solutions have been used that have a high dissolution reaction rate for the material that makes up the seed layer (i.e., etching solutions in which the diffusion of reactive species in the etching solution to the vicinity of the etching target determines the etching rate.) If the distance between adjacent coil wiring portions is shortened or the thickness of the coil wiring is increased, it becomes difficult for the etching solution to be supplied between the adjacent coil wiring portions.

[0072] As a result, when using the above-mentioned etching solution, the etching variation to the seed layer becomes large, and the etching amount increases in order to reliably remove the seed layer. For these reasons, it has not been possible to shorten the distance between adjacent coil wiring portions or to increase the thickness of the coil wiring in the past.

[0073] The coil device 100 has a printed wiring board 10. In the etching step S6 of the printed wiring board 10, an etching solution having a low dissolution reaction rate with respect to the material constituting the second layer 12ab is used. As a result, the etching rate in the etching step S6 is determined by the reaction between reactive species in the etching solution and the etching target, and even if it is difficult to supply the etching solution between adjacent first electroplated layers 12b, variations in the etching of the seed layer 12a (second layer 12ab) are unlikely to occur.

[0074] Therefore, according to the coil device 100, the pattern density of the coil wiring 12 can be increased and the thickness T can be made larger.

[0075] Furthermore, land 13a has a width W larger than that of the spirally wound portion of first coil wiring 13, and land 14a has a width W larger than that of the spirally wound portion of second coil wiring 14. Therefore, the plating growth rate is fast on lands 13a and 14a, and thickness T tends to be large.

[0076] When the difference between the thickness T at the land 13a and the thickness T at the portion of the first coil wiring 13 that is wound in a spiral shape and the difference between the thickness T at the land 14a and the thickness T at the portion of the second coil wiring 14 that is wound in a spiral shape become large, it becomes necessary to increase the thicknesses T1 and T2 in order to cover the first coil wiring 13 and the second coil wiring 14 with the first layer 21 and the third layer 31, respectively.

[0077] However, in the coil device 100, the difference between the thickness T at the land 13a and the thickness T at the portion of the first coil wiring 13 that is wound in a spiral shape, and the difference between the thickness T at the land 14a and the thickness T at the portion of the second coil wiring 14 that is wound in a spiral shape are small, so that the thicknesses T1 and T2 can be made small.

[0078] Thus, in the coil device 100, the pattern density of the coil wiring 12 increases, the thickness T increases, and the thicknesses T1 and T2 decrease, so that the value obtained by dividing the total mass of the first coil wiring 13, the second coil wiring 14, and the conductive portion 15 by the total volume of the base film 11, the first coil wiring 13, the second coil wiring 14, the first protective layer 20, the second protective layer 30, and the conductive portion 15 increases. More specifically, in the coil device 100, the value obtained by dividing the total mass of the first coil wiring 13, the second coil wiring 14, and the conductive portion 15 by the total volume of the base film 11, the first coil wiring 13, the second coil wiring 14, the first protective layer 20, the second protective layer 30, and the conductive portion 15 (value A / B) is 2.0 g / cm. 3 It can be more than that.

[0079] When soldering the coil device 100 to the substrate 60, the solder alloy is melted on the terminals 61. If the value obtained by dividing the total mass of the first coil wiring 13, the second coil wiring 14, and the conductive portion 15 by the total volume of the base film 11, the first coil wiring 13, the second coil wiring 14, the first protective layer 20, the second protective layer 30, and the conductive portion 15 is small, the coil device 100 will tilt due to the surface tension of the molten solder alloy, and it will be impossible to ensure horizontality when soldering the coil device 100 to the substrate 60. However, the coil device 100 has a density of 2.0 g / cm 3 As a result of the above, horizontality can be ensured when soldering to the substrate 60.

[0080] Table 1 shows the relationship between the soldering yield rate and the density of the coil device. When the angle between the back surface of the coil device (the surface opposite to the surface where soldering is performed) and the surface of the board was within ±3°, it was determined that the soldering was performed well. The percentages of coil devices that were determined to be soldered well were designated A, B, C, D, and E, respectively, for cases where the percentage was 99% or more, 96% or more but less than 99%, 90% or more but less than 96%, 70% or more but less than 90%, and less than 70%. The density of the coil device in Table 1 is the sum of the masses of the first coil wiring 13, the second coil wiring 14, and the conductive portion 15 divided by the sum of the volumes of the base film 11, the first coil wiring 13, the second coil wiring 14, the first protective layer 20, the second protective layer 30, and the conductive portion 15.

[0081] [Table 1]

[0082] As shown in Table 1, the density of the coil device is 2.0 g / cm 3 When the density of the coil device was less than 2.0 g / cm, the rate of non-defective soldering was less than 90 percent (the rating was D or E). 3 When the density of the coil device was 2.0 g / cm or more, the rate of good soldering was 90% or more (the rating was A, B, or C). 3 It has been experimentally demonstrated that solderability is improved when the temperature is above this level.

[0083] If the value obtained by dividing the total mass of the first coil wiring 13, the second coil wiring 14, and the conductive portion 15 by the total volume of the base film 11, the first coil wiring 13, the second coil wiring 14, the first protective layer 20, the second protective layer 30, and the conductive portion 15 is too large, when soldering the coil device 100 to the substrate 60, the solder alloy between the external connection terminal 41 (plating layer 42) and the terminal 61 will be pushed out from between the external connection terminal 41 (plating layer 42) and the terminal 61 due to the weight of the coil device 100. If the solder alloy between the external connection terminal 41 (plating layer 42) and the terminal 61 is pushed out, there is a risk that the connection between the external connection terminal 41 (plating layer 42) and the terminal 61 will be poor.

[0084] Therefore, the coil device 100 has a density of 7.0 g / cm 3 By setting the following, connection defects between the external connection terminal 41 and the terminal 61 can be suppressed.

[0085] (Variation 1) Fig. 12 is a cross-sectional view of a coil device 100 according to Modification 1. As shown in Fig. 12, the coil device 100 does not necessarily have to have wiring 40, plating layer 42, and solder resist 50. In this case, the end of the first coil wiring 13 opposite to the land 13a serves as a terminal portion 13b, and a through hole is formed in the first protective layer 20 to expose the terminal portion 13b.

[0086] (Variation 2) Fig. 13 is a cross-sectional view of a coil device 100 according to Modification 2. As shown in Fig. 13, the printed wiring board 10 may have dummy wiring 17. The dummy wiring 17 has a first dummy wiring 18 and a second dummy wiring 19. The first dummy wiring 18 is arranged on the first main surface 11a, and the second dummy wiring 19 is arranged on the second main surface 11b.

[0087] The dummy wiring 17 is electrically isolated from the coil wiring 12. More specifically, the first dummy wiring 18 is not connected to the first coil wiring 13, and the second dummy wiring 19 is not connected to the second coil wiring 14. Like the coil wiring 12, the dummy wiring 17 (first dummy wiring 18, second dummy wiring 19) has a seed layer 12a, a first electrolytic plated layer 12b, and a second electrolytic plated layer 12c. Furthermore, the first dummy wiring 18 and the second dummy wiring 19 are covered with a first protective layer 20 (first layer 21) and a second protective layer 30 (third layer 31), respectively.

[0088] If the total mass of the first coil wiring 13, the second coil wiring 14, the conductive portion 15, and the dummy wiring 17 is E, and the total volume of the base film 11, the first coil wiring 13, the second coil wiring 14, the first protective layer 20, the second protective layer 30, the conductive portion 15, and the dummy wiring 17 is F, the value of E / F is 2.0 g / cm 3 That's all.

[0089] When calculating the value (E / F value) obtained by dividing the total mass of the first coil wiring 13, the second coil wiring 14, the conductive portion 15, and the dummy wiring 17 by the total volume of the base film 11, the first coil wiring 13, the second coil wiring 14, the first protective layer 20, the second protective layer 30, the conductive portion 15, and the dummy wiring 17, first, the volume of each component of the coil device 100 measured using X-ray CT is calculated. That is, the layer configuration and dimensions of the base film 11, the first coil wiring 13, the second coil wiring 14, the first protective layer 20, the second protective layer 30, the conductive portion 15, and the dummy wiring 17 of the coil device 100 are measured to calculate the volume of each of these components, and then the total is calculated.

[0090] Second, the total mass of the first coil wiring 13, the second coil wiring 14, the conductive portion 15 and the dummy wiring 17 is calculated by multiplying the total volume of the first coil wiring 13, the second coil wiring 14, the conductive portion 15 and the dummy wiring 17 by the copper density, which is a known value.

[0091] As a result of the above, the total mass of the first coil wiring 13, the second coil wiring 14, the conductive portion 15, and the dummy wiring 17 and the total volume of the base film 11, the first coil wiring 13, the second coil wiring 14, the first protective layer 20, the second protective layer 30, the conductive portion 15, and the dummy wiring 17 are obtained, and the value (E / F value) obtained by dividing the total mass of the first coil wiring 13, the second coil wiring 14, the conductive portion 15, and the dummy wiring 17 by the total volume of the base film 11, the first coil wiring 13, the second coil wiring 14, the first protective layer 20, the second protective layer 30, the conductive portion 15, and the dummy wiring 17 can be calculated.

[0092] Since the dummy wiring 17 also contains copper like the coil wiring 12, forming the dummy wiring 17 in addition to the coil wiring 12 increases the density of the coil device 100. Therefore, by forming the dummy wiring 17, it is possible to adjust the density of the coil device 100.

[0093] (Variation 3) Fig. 14 is a cross-sectional view of a coil device 100 according to Modification 3. As shown in Fig. 14, the coil device 100 may further include an adhesive layer 71, a base film 72, a third coil wiring 73, an adhesive layer 74, a base film 75, a fourth coil wiring 76, an adhesive layer 77, a base film 78, an adhesive layer 79, and a base film 80. Although not shown, the coil device 100 according to Modification 3 may further include a first conductive connecting portion and a second conductive connecting portion.

[0094] The adhesive layer 71 is made of an adhesive. The adhesive layer 71 is disposed on the first main surface 11a so as to cover the first coil wiring 13. The base film 72 is disposed on the adhesive layer 71. The base film 72 is made of a material such as polyimide. The base film 72 has a third main surface 72a and a fourth main surface 72b. The third main surface 72a faces the adhesive layer 71, and the fourth main surface 72b is the surface opposite the third main surface 72a.

[0095] The third coil wiring 73 includes a seed layer made up of a first layer 73aa disposed on the fourth main surface 72b and a second layer 73ab disposed on the first layer 73aa, and a second layer 73ab disposed on the seed layer. Do The third coil wiring 73 has an electroplated layer 73b disposed on the seed layer. The constituent materials of the first layer 73aa and the second layer 73ab are not limited, but include, for example, a nickel-chromium alloy and copper, respectively. The constituent material of the electroplated layer 73b is, for example, copper. The third coil wiring 73 may further have another electroplated layer made of copper that covers the side surfaces of the seed layer and the side surfaces and top surface of the electroplated layer 73b.

[0096] The adhesive layer 74 is made of an adhesive. The adhesive layer 74 is disposed on the second main surface 11b so as to cover the second coil wiring 14. The base film 75 is disposed on the adhesive layer 74. The base film 75 is made of a material such as polyimide. The base film 75 has a fifth main surface 75a and a sixth main surface 75b. The fifth main surface 75a faces the adhesive layer 74, and the sixth main surface 75b is the surface opposite the fifth main surface 75a.

[0097] The fourth coil wiring 76 includes a seed layer made up of a first layer 76aa disposed on the sixth main surface 75b and a second layer 76ab disposed on the first layer 76aa, and a second layer 76ab disposed on the seed layer. Do The fourth coil wiring 76 has an electroplated layer 76b disposed on the seed layer. The constituent materials of the first layer 76aa and the second layer 76ab are not limited, but include, for example, a nickel-chromium alloy and copper, respectively. The constituent material of the electroplated layer 76b is, for example, copper. Note that the fourth coil wiring 76 may further have another electroplated layer made of copper that covers the side surfaces of the seed layer and the side surfaces and top surface of the electroplated layer 76b.

[0098] The adhesive layer 77 is made of an adhesive. The adhesive layer 77 is disposed on the fourth main surface 72b so as to cover the third coil wiring 73. The base film 78 is disposed on the adhesive layer 77. The base film 78 is made of a material such as polyimide. The base film 78 has a seventh main surface 78a and an eighth main surface 78b. The seventh main surface 78a faces the adhesive layer 77, and the eighth main surface 78b is the surface opposite the seventh main surface 78a. The external connection terminal 41 is disposed on the eighth main surface 78b. The adhesive layer 79 is made of an adhesive. The adhesive layer 79 is disposed on the sixth main surface 75b so as to cover the fourth coil wiring 76. The base film 80 is disposed on the adhesive layer 79.

[0099] It should be noted that first coil wiring 13 and second coil wiring 14 may or may not have second electrolytic plated layer 12c.

[0100] As described above, the coil device 100 according to the third modification may further include a first conductive connecting portion and a second conductive connecting portion (not shown). The base film 72 may have a through hole (not shown) formed therein, penetrating the base film 72 in the thickness direction. The first conductive connecting portion is embedded in the through hole formed in the base film 72 and connects the first coil wiring 13 and the third coil wiring 73, thereby electrically connecting the first coil wiring 13 and the third coil wiring 73. The base film 75 may have a through hole (not shown) formed therein, penetrating the base film 75 in the thickness direction. The second conductive connecting portion is embedded in the through hole formed in the base film 75 and connects the second coil wiring 14 and the fourth coil wiring 76, thereby electrically connecting the second coil wiring 14 and the fourth coil wiring 76.

[0101] If the total mass of the first coil wiring 13, the second coil wiring 14, the conductive portion 15, the third coil wiring 73, the fourth coil wiring 76, the first conductive connecting portion, and the second conductive connecting portion is G, and the total volume of the base film 11, the first coil wiring 13, the second coil wiring 14, the conductive portion 15, the third coil wiring 73, the fourth coil wiring 76, the adhesive layer 71, the base film 72, the adhesive layer 74, the base film 75, the adhesive layer 77, the base film 78, the adhesive layer 79, the base film 80, the first conductive connecting portion, and the second conductive connecting portion is H, the value of G / H is 2.0 g / cm 3 That is, when the coil device 100 has a plurality of printed wiring boards, if the density of the coil device 100 is 2.0 g / cm 3 It may be more than that.

[0102] If the total volume of the base film 11, the first coil wiring 13, the second coil wiring 14, the conductive portion 15, the third coil wiring 73, the fourth coil wiring 76, the adhesive layer 71, the base film 72, the adhesive layer 74, the base film 75, the adhesive layer 77, the base film 78, the adhesive layer 79, the base film 80, the first conductive connection portion, and the second conductive connection portion is I, and the volume of copper contained in the first coil wiring 13, the second coil wiring 14, the conductive portion 15, the third coil wiring 73, the fourth coil wiring 76, the first conductive connection portion, and the second conductive connection portion is J, it is preferable that the value of J / I x 100 is greater than or equal to 10 percent and less than or equal to 70 percent.

[0103] A multilayer substrate including the coil device 100 shown in FIG. 1 or the coil device 100 according to Modification 1, Modification 2, or Modification 3 is also included in the embodiments of the present disclosure.

[0104] 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. [Explanation of symbols]

[0105] L: distance, S1: preparation step, S2: seed layer formation step, S3: resist formation step, S4: first electrolytic plating step, S5: resist removal step, S6: etching step, S7: second electrolytic plating step, T: thickness, W: width, 100: coil device, 10: printed wiring board, 11: base film, 11a: first main surface, 11b: second main surface, 11c: through hole, 12: coil wiring, 12a: seed layer, 12aa: first layer, 12ab: second layer, 12b: first electrolytic plating layer, 12c: second electrolytic plating layer, 13: first coil wiring, 13a: land, 13b: terminal portion, 14: second coil wiring, 14a: land, 15: conductive portion, 16: resist, 17: dummy wiring, 18: first dummy wiring, 19: second dummy wiring, 20: first protective layer, 21: first layer, 22: second layer, 30: second protective layer, 31 Third layer, 32 Fourth layer, 40 Wiring, 41 External connection terminal, 42 Plating layer, 60 Substrate, 61 Terminal, 62 Connection layer, 50 Solder resist, 71 Adhesive layer, 72 Base film, 72a Third main surface, 72b Fourth main surface, 73 Third coil wiring, 73aa First layer, 73ab Second layer, 73b Electroplated layer, 74 Adhesive layer, 75 Base film, 75a Fifth main surface, 75b Sixth main surface, 76 Fourth coil wiring, 77 Adhesive layer, 78 Base film, 78a Seventh main surface, 78b Eighth main surface, 79 Adhesive layer, 80 Base film.

Claims

1. A coil device, a base film having a first major surface and a second major surface; a first coil wiring disposed on the first main surface and having a portion wound in a spiral shape; and, a second coil wiring disposed on the second main surface and having a portion wound in a spiral shape; a first protective layer disposed on the first main surface so as to cover the first coil wiring; a second protective layer disposed on the second main surface so as to cover the second coil wiring; a conductive portion; The base film has a through hole formed therein, the through hole passing through the base film along a thickness direction, the conductive portion is embedded in the through hole and connected to the first coil wiring and the second coil wiring, thereby electrically connecting the first coil wiring and the second coil wiring; When the total mass of the first coil wiring, the second coil wiring, and the conductive portion is A, and the total volume of the base film, the first coil wiring, the second coil wiring, the first protective layer, the second protective layer, and the conductive portion is B, the value of A / B is 2.0 g / cm ３ That's all, a wiring disposed on the first protective layer and electrically connected to the first coil wiring; an external connection terminal disposed on the wiring; a solder resist disposed on the wiring and the first protective layer so as to expose the external connection terminals, the first protective layer includes a first layer disposed on the first main surface so as to cover the first coil wiring, and a second layer disposed on the first layer; the second protective layer includes a third layer disposed on the second main surface so as to cover the second coil wiring, and a fourth layer disposed on the third layer; the base film, the second layer, and the fourth layer are formed of polyimide, the first layer and the third layer are formed of an adhesive; the external connection terminals are connected to the substrate via a solder alloy; The coil device has a height, width and length of 100 μm or more and 500 μm or less, 2 mm or more and 10 mm or less and 2 mm or more and 40 mm or less, respectively.

2. the first coil wiring, the second coil wiring, and the conductive portion contain copper, 2. The coil device of claim 1, wherein the total volume of the base film, the first coil wiring, the second coil wiring, the first protective layer, the second protective layer, and the conductive portion is C, and the total volume of copper contained in the first coil wiring, the second coil wiring, and the conductive portion is D, and the value of D / C x 100 is greater than or equal to 10 percent and less than or equal to 70 percent.

3. The coil device according to claim 1 , wherein the first layer and the third layer have a thickness of 2 μm or more and 100 μm or less.

4. a distance between two adjacent portions of the first coil wiring and a distance between two adjacent portions of the second coil wiring are 2 μm or more and 20 μm or less; a thickness of the first coil wiring and a thickness of the second coil wiring are 30 μm or more and 80 μm or less; The coil device according to claim 1 , wherein the width of the first coil wiring and the width of the second coil wiring are not less than 10 μm and not more than 100 μm.

5. The coil device according to claim 1, wherein the value obtained by dividing the thickness of the first coil wiring by the width of the first coil wiring and the value obtained by dividing the thickness of the second coil wiring by the width of the second coil wiring are greater than or equal to 1.0 and less than or equal to 3.

0.

6. A coil device, a base film having a first major surface and a second major surface; a first coil wiring disposed on the first main surface and having a portion wound in a spiral shape; a second coil wiring disposed on the second main surface and having a spirally wound portion; a first protective layer disposed on the first main surface so as to cover the first coil wiring; a second protective layer disposed on the second main surface so as to cover the second coil wiring; A conductive portion; a dummy wiring that is electrically separated from the first coil wiring and the second coil wiring and that is disposed on at least one of the first main surface and the second main surface, The base film has a through hole formed therein, the through hole passing through the base film along a thickness direction, the conductive portion is embedded in the through hole and connected to the first coil wiring and the second coil wiring, thereby electrically connecting the first coil wiring and the second coil wiring; When the total mass of the first coil wiring, the second coil wiring, the conductive portion, and the dummy wiring is E, and the total volume of the base film, the first coil wiring, the second coil wiring, the first protective layer, the second protective layer, the conductive portion, and the dummy wiring is F, the value of E / F is 2.0 g / cm ３ That's all, a wiring disposed on the first protective layer and electrically connected to the first coil wiring; and an external connection terminal disposed on the wiring; a solder resist disposed on the wiring and the first protective layer so as to expose the external connection terminals, the first protective layer includes a first layer disposed on the first main surface so as to cover the first coil wiring, and a second layer disposed on the first layer; the second protective layer includes a third layer disposed on the second main surface so as to cover the second coil wiring, and a fourth layer disposed on the third layer; the base film, the second layer, and the fourth layer are formed of polyimide, the first layer and the third layer are formed of an adhesive; the external connection terminals are connected to the substrate via a solder alloy; The coil device has a height, width and length of 100 μm or more and 500 μm or less, 2 mm or more and 10 mm or less and 2 mm or more and 40 mm or less, respectively.

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