Okuzawa, Nobuyuki (Tokyo, JP)
Yoshida, Makoto (Tokyo, JP)

Plaque It! Sponsored by: Flash of Genius

11/528410

08/19/2008

09/28/2006

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TDK Corporation (Tokyo, JP)

336/200

29/602.1, 336/232, 336/223

H01F5/00; H01F7/06

29/605, 336/200, 29/606, 29/602.1, 336/232, 336/223

5372967	Method for fabricating a vertical trench inductor	December, 1994	Sundaram et al.
6008102	Method of forming a three-dimensional integrated inductor	December, 1999	Alford et al.
6114937	Integrated circuit spiral inductor	September, 2000	Burghartz et al.	336/200
6696912	Integrated circuit inductor with a magnetic core	February, 2004	Ahn et al.	336/200
6876285	High density multi-layer microcoil and method for fabricating the same	April, 2005	Liang et al.
6992557	Printed inductor capable of raising Q value	January, 2006	Aoyagi	336/200
7088215	Embedded duo-planar printed inductor	August, 2006	Winter et al.	336/200

JPB23601619

October, 2004

Mai, Anh T.

Oliff & Berridge, PLC

What is claimed is:

1. A common mode choke coil, comprising: a first helical coil unit having a plurality of elongate first conductive layers arranged in parallel on a bottom insulation layer, second conductive layers formed on both ends of the first conductive layers; and a third conductive layer formed on the second conductive layers, which is electrically connected to the second conductive layer at one end thereof and which is electrically connected, at another end thereof, to the second conductive layer formed on the first conductive layer adjacent to the first conductive layer directly under the second conductive layer, one turn of the coil being formed by the first conductive layer, the second conductive layer, the third conductive layer and the another second conductive layer; and a second helical coil unit having a configuration similar to that of the first helical coil unit, wherein a first imaginary plane including three conductive layers among the first, second, third, and the another second conductive layers forming one turn of the coil of the first helical coil unit and a second imaginary plane including three conductive layers among the first, second, third, and the another second conductive layers forming one turn of the coil of the second helical coil unit are substantially orthogonal to axes of spiral of the first and second helical coil units.

2. A common mode choke coil according to claim 1, further comprising: a core extending through the first and second helical coil units on the side of the inner circumferences thereof; and a magnetic member part connected to the core and cooperating with the core to form a closed magnetic path.

3. A common mode choke coil according to claim 2, wherein the closed magnetic path is formed substantially parallel to the surface on which the first conductive layers are formed.

4. A common mode choke coil according to claim 2, wherein the closed magnetic path is formed substantially orthogonal to the surface on which the first conductive layers are formed.

5. A common mode choke coil according to claim 2, wherein the core is formed from a material having a high permeability.

6. A common mode choke coil according to claim 1, wherein, when an element forming surface is viewed in the normal direction thereof, the first and second helical coils are formed like comb teeth and are interdigitated with each other.

7. A common mode choke coil according to claim 1, wherein the first and second imaginary planes are substantially orthogonal to the extending direction of the core.

8. A common mode choke coil according to claim 1, wherein the conductive layer which is not included in the first imaginary plane among the first, second, third and the another second conductive layers forming one turn of the coil of the first helical coil unit is formed so as not to extend across the second imaginary plane and wherein the conductive layer which is not included in the second imaginary plane among the first, second, third and the another second conductive layers forming one turn of the coil of the second helical coil unit is formed so as not to extend across the first imaginary plane.

9. A method of manufacturing a common mode choke coil, comprising: forming a first electrode film on a substrate; forming a first resist layer on the first electrode film; forming a plurality of elongated first openings in parallel in the first resist layer to expose the first electrode film; forming each of first conductive layers electrically connected to the first electrode film through the first openings using a plating process; forming a second resist layer on the entire surface after removing the first resist layer; forming a plurality of second openings for exposing both ends of the first conductive layers in the second resist layer; forming each of second conductive layers electrically connected to the first conductive layers through the second openings using a plating process; removing the second resist layer and the first electrode film under the second resist layer; forming a first insulation layer on which the tops of the second conductive layers are exposed; forming a second electrode film electrically connected to the second conductive layers on the first insulation layer; forming a third resist layer on the second electrode film; forming the third resist layer with a plurality of elongated third openings arranged in parallel to expose the second electrode film in positions where the openings overlap the second conductive layers at one end thereof and overlap, at another end thereof, the second conductive layers formed on the first conductive layer adjacent to the first conductive layer directly under the second conductive layer when the substrate surface is viewed in the normal direction thereof; forming each of third conductive layers electrically connected to the second electrode film through the third openings using a plating process; removing the third resist layer and the second electrode film under the third resist layer; forming a first helical coil unit one turn of which is formed by the first, second, third, and the another second conductive layers; similarly forming a second helical coil unit simultaneously with the first helical coil unit; forming a first intermediate electrode film between the second conductive layers and the second electrode film; forming a first intermediate resist layer on the first intermediate electrode film; forming the first intermediate resist layer with a first intermediate opening exposing the first intermediate electrode film and extending across the first conductive layers when the substrate surface is viewed in the normal direction thereof; forming a first magnetic member layer on the first intermediate electrode film in the first intermediate opening using a plating process; removing the first intermediate resist layer and the first intermediate electrode film under the first intermediate resist layer; forming a core constituted by the first magnetic member layer and extending through the first and second helical coil units on a side of an inner circumference thereof; forming a second intermediate electrode film electrically connected to the second conductive layers on the entire surface; forming a second intermediate resist layer on the second intermediate electrode film; forming a second intermediate opening in the second intermediate resist layer to expose the second intermediate electrode film on the second conductive layer; forming a first intermediate conductive layer electrically connected to the second intermediate electrode film through the second intermediate opening using a plating process; removing the second intermediate resist layer and the second intermediate electrode film under the second intermediate resist layer; forming a second insulation layer on the first insulation layer with the first intermediate conductive layer exposed; and forming the first and second helical coil units with the second electrode film electrically connected to the second conductive layers through the second intermediate electrode film and the first intermediate conductive layer.

10. A method of manufacturing a common mode choke coil according to claim 9, further comprising: forming an organic insulating material in a gap between the first and second helical coil units; and heating and curing the organic insulating material to insulate the first and second helical coil units from each other.

11. A method of manufacturing a common mode choke coil according to claim 9, further comprising: forming the first intermediate opening in an annular shape; and forming a magnetic member part forming a closed magnetic path in cooperation with the core in the first intermediate opening at the same time when the core is formed.

12. A method of manufacturing a common mode choke coil according to claim 9, further comprising: removing the first intermediate resist layer instead of the step of removing the first intermediate resist layer and the first intermediate electrode film under the first intermediate resist layer; forming a third intermediate resist layer on the first intermediate electrode film and the first magnetic member layer; forming the third intermediate resist layer with a third intermediate opening for exposing both ends of the first magnetic member layer; forming a second magnetic member layer on the first magnetic member layer in the third intermediate opening using a plating process; forming the core by removing the third intermediate resist layer and the first intermediate electrode film under the same; forming a third electrode film on the second insulation layer and the second magnetic member layer after forming the first and second helical coil units; forming a fourth resist layer on the third electrode film; forming the fourth resist layer with a fourth opening for exposing the third electrode film on the second magnetic member layer; forming a third magnetic member layer on the third electrode film in the fourth opening using a plating process; removing the fourth resist layer and the third electrode film under the same; forming a third insulation layer on which the third magnetic member layer is exposed; forming a fourth electrode film on the third insulation layer; forming a fifth resist layer on the fourth electrode film; forming the fifth resist layer with a fifth opening for exposing the fourth electrode film on the third magnetic member layer on both ends thereof; forming a fourth magnetic member layer on the fourth electrode film in the fifth opening using a plating process; and forming a closed magnetic path constituted by the core and the second, third, and fourth magnetic member layers by removing the fifth resist layer and the fourth conductive film under the fifth resist layer.

13. A method of manufacturing a common mode choke coil, comprising: forming a first electrode film on a substrate; forming a first resist layer on the first electrode film; forming a plurality of elongated first openings in parallel in the first resist layer to expose the first electrode film; forming each of first conductive layers electrically connected to the first electrode film through the first openings using a plating process; forming a second resist layer on the entire surface after removing the first resist layer; forming a plurality of second openings for exposing both ends of the first conductive layers in the second resist layer; forming each of second conductive layers electrically connected to the first conductive layers through the second openings using a plating process; removing the second resist layer and the first electrode film under the second resist layer; forming a first insulation layer on which the tops of the second conductive layers are exposed; forming a second electrode film electrically connected to the second conductive layers on the first insulation layer; forming a third resist layer on the second electrode film; forming the third resist layer with a plurality of elongated third openings arranged in parallel to expose the second electrode film in positions where the openings overlap the second conductive layers at one end thereof and overlap, at another end thereof, the second conductive layers formed on the first conductive layer adjacent to the first conductive layer directly under the second conductive layer when the substrate surface is viewed in the normal direction thereof; forming each of third conductive layers electrically connected to the second electrode film through the third openings using a plating process; removing the third resist layer and the second electrode film under the third resist layer; forming a first helical coil unit one turn of which is formed by the first, second, third, and the another second conductive layers; and similarly forming a second helical coil unit simultaneously with the first helical coil unit; forming a first intervening resist layer between the second conductive layer and the second electrode film after forming the first insulation layer; forming the first intervening resist layer with a first intervening opening exposing the first insulation layer and extending across the first conductive layer when the substrate surface is viewed in the normal direction thereof; forming a groove on the first insulation layer under the first intervening opening; removing the first intervening resist layer; forming a first intervening electrode film in the groove and on the first insulation layer; forming a first magnetic member layer on the first intervening electrode film in the groove using a plating process; forming a core constituted by the first magnetic member layer and extending through the first and second helical coil units on the side of the inner circumferences thereof; and forming the second electrode film on the first insulation layer.

14. A method of manufacturing a common mode choke coil according to claim 13, further comprising: forming the first intervening opening in an annular shape; and forming a magnetic member part forming a closed magnetic path in cooperation with the core in the first intervening opening at the same time when the core is formed.

15. A method of manufacturing a common mode choke coil according to claim 13, further comprising: forming a second intervening resist electrode film on the first insulation layer after forming the first insulation layer; forming a second intervening resist layer on the second intervening electrode film; forming the second intervening resist layer with a second intervening opening for exposing the second intervening electrode film on both ends of the core; forming a second magnetic member layer on the second intervening electrode film in the second intervening opening using a plating process; removing the second intervening resist layer and the second intervening electrode film under the second intervening resist layer; forming the second electrode film on the first insulation layer; forming a second insulation layer for exposing the second magnetic member layer after forming the first and second helical coil units; forming a third electrode film on the second insulation layer; forming a fourth resist layer on the third electrode film; forming the fourth resist layer with a fourth opening exposing the third electrode film on the second magnetic member layer at both ends thereof; forming a third magnetic member layer on the third electrode film in the fourth opening using a plating process; and forming a closed magnetic path constituted by the core and the second and third magnetic member layers by removing the fourth resist layer and the third electrode film under the fourth resist layer.

16. A method of manufacturing a common mode choke coil according to claim 13, comprising: forming an organic insulating material in a gap between the first and second helical coil units; and heating and curing the organic insulating material to insulate the first and second helical coil units from each other.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a common mode choke coil and a method of manufacturing the same.

2. Description of the Related Art

Known coil components mounted on internal circuits of electronic apparatus such as personal computers and portable telephones include wire-wound types provided by winding a copper wire around a ferrite core, multi-layer types provided by forming a coil conductor pattern on a magnetic sheet made of ferrite etc. and stacking such magnetic sheets one over another, and thin-film types provided by alternately forming insulation films and metal thin-film coil conductors using a thin film forming technique. Recently, there is a rapid trend toward electronic apparatus having smaller sizes and higher performance, which has resulted in strong demand for coil components having smaller sizes and higher performance. Referring to thin-film type coil components, coil components of a chip size of 1 mm or less are supplied to the market by providing coil conductors having smaller thickness.

Coil components include common mode choke coils for suppressing a common mode current which can cause electromagnetic interference in a balanced transmission system and inductors which are combined with a capacitor to provide a low-pass filter (LPF). Patent Document 1 discloses a thin-film type common mode choke coil having an insulation layer and a spiral coil conductor formed using a thin film forming technique between a pair of magnetic substrates disposed opposite to each other. Patent Documents 2 and 3 disclose thin-film type inductors and methods of manufacturing the same. Patent Document 4 discloses a thin-film type micro-coil having a core and a method of manufacturing the same.

Patent Document 1: Japanese Patent No. 3601619

Patent Document 2: U.S. Pat. No. 6,008,102

Patent Document 3: U.S. Pat. No. 5,372,967

Patent Document 4: U.S. Pat. No. 6,876,285

Further size reduction of common mode choke coils is still required. However, in the case of the common mode choke coil according to the related art disclosed in Patent Document 1, it is required to increase the number of turns of the coil conductor to improve electrical characteristics such as impedance characteristics, for example. As a result, the coil conductor must be formed in a larger area, and a problem arises in that it will be difficult to reduce the size of the common mode choke coil.

Further, since the common mode choke coil according to the related art has a pair of magnetic substrates disposed opposite to each other, there is a problem in that it is difficult to provide the choke coil with a low profile.

The common mode choke coil according to the related art is completed through a thin film forming step for forming an insulation layer and a coil conductor (coil layer) on a magnetic substrate in the form of a wafer using a thin film forming technique such as a photo-process, a substrate combining step for combining the substrate with another magnetic substrate by bonding them using a bonding layer formed on the insulation layer, a cutting step for cutting the wafer to divide it into chips, and an external electrode forming step for forming an external electrode. As thus described, the manufacture of a common mode choke coil involves a plurality of manufacturing steps and therefore requires a high manufacturing cost, which results in a problem in that the cost of the common mode choke coil is increased.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a common mode choke coil having high electrical characteristics, a small size, and a low profile at a low cost and to provide a method of manufacturing the same.

The above-described object is achieved by a common mode choke coil comprising:

a first helical coil unit having a plurality of elongate first conductive layers arranged in parallel on a bottom insulation layer, second conductive layers formed on both ends of the first conductive layers, and a third conductive layer formed on the second conductive layers, which is electrically connected to the second conductive layer at one end thereof and which is electrically connected, at another end thereof, to the second conductive layer formed on the first conductive layer adjacent to the first conductive layer directly under the second conductive layer, one turn of the coil being formed by the first conductive layer, the second conductive layer, the third conductive layer and the another second conductive layer; and

a second helical coil unit having a configuration similar to that of the first helical coil unit.

The common mode choke coil according to the invention is characterized in that it includes:

a core extending through the first and second helical coil units on the side of the inner circumferences thereof; and

a magnetic member part connected to the core and cooperating with the core to form a closed magnetic path.

The common mode choke coil according to the invention is characterized in that the closed magnetic path is formed substantially parallel to the surface on which the first conductive layers are formed.

The common mode choke coil according to the invention is characterized in that the closed magnetic path is formed substantially orthogonal to the surface on which the first conductive layers are formed.

The common mode choke coil according to the invention is characterized in that the core is formed from a material having a high permeability.

The common mode choke coil according to the invention is characterized in that a first imaginary plane including three conductive layers among the first, second, third, and second conductive layers forming one turn of the coil of the first helical coil unit and a second imaginary plane including three conductive layers among the first, second, third, and second conductive layers forming one turn of the coil of the second helical coil unit are substantially orthogonal to axes of spiral of the first and second helical coil units.

The common mode choke coil according to the invention is characterized in that the first and second imaginary planes are substantially orthogonal to the extending direction of the core.

The common mode choke coil according to the invention is characterized in that the conductive layer which is not included in the first imaginary plane among the first, second, third and second conductive layers forming one turn of the coil of the first helical coil unit is formed so as not to extend across the second imaginary plane and in that the conductive layer which is not included in the second imaginary plane among the first, second, third and second conductive layers forming one turn of the coil of the second helical coil unit is formed so as not to extend across the first imaginary plane.

The above-described object is achieved by a method of manufacturing a common mode choke coil, comprising the steps of:

forming a first electrode film on a substrate;

forming a first resist layer on the first electrode film;

forming a plurality of elongate first openings in parallel in the first resist layer to expose the first electrode film;

forming each of first conductive layers electrically connected to the first electrode film through the first openings using a plating process;

forming a second resist layer on the entire surface after removing the first resist layer;

forming a plurality of second openings for exposing both ends of the first conductive layers in the second resist layer;

forming each of second conductive layers electrically connected to the first conductive layers through the second openings using a plating process;

removing the second resist layer and the first electrode film under the second resist layer;

forming a first insulation layer on which the tops of the second conductive layers are exposed;

forming a second electrode film electrically connected to the second conductive layers on the first insulation layer;

forming a third resist layer on the second electrode film;

forming the third resist layer with a plurality of elongate third openings arranged in parallel to expose the second electrode film in positions where the openings overlap the second conductive layers at one end thereof and overlap, at another end thereof, the second conductive layers formed on the first conductive layer adjacent to the first conductive layer directly under the second conductive layer when the substrate surface is viewed in the normal direction thereof;

forming each of third conductive layers electrically connected to the second electrode film through the third openings using a plating process;

removing the third resist layer and the second electrode film under the third resist layer;

forming a first helical coil unit one turn of which is formed by the first, second, third, and second conductive layers; and

similarly forming a second helical coil unit simultaneously with the first helical coil unit.

The method of manufacturing a common mode choke coil according to the invention is characterized in that it includes the steps of:

forming a first intermediate electrode film between the second conductive layers and the second electrode film;

forming a first intermediate resist layer on the first intermediate electrode film;

forming the first intermediate resist layer with a first intermediate opening exposing the first intermediate electrode film and extending across the first conductive layers when the substrate surface is viewed in the normal direction thereof;

forming a first magnetic member layer on the first intermediate electrode film in the first intermediate opening using a plating process;

removing the first intermediate resist layer and the first intermediate electrode film under the first intermediate resist layer;

forming a core constituted by the first magnetic member layer and extending through the first and second helical coil units on the side of the inner circumference thereof;

forming a second intermediate electrode film electrically connected to the second conductive layers on the entire surface;

forming a second intermediate resist layer on the second intermediate electrode film;

forming a second intermediate opening in the second intermediate resist layer to expose the second intermediate electrode film on the second conductive layer;

forming a first intermediate conductive layer electrically connected to the second intermediate electrode film through the second intermediate opening using a plating process;

removing the second intermediate resist layer and the second intermediate electrode film under the second intermediate resist layer;

forming a second insulation layer on the first insulation layer with the first intermediate conductive layer exposed; and

forming the first and second helical coil units with the second electrode film electrically connected to the second conductive layers through the second intermediate electrode film and the first intermediate conductive layer.

The method of manufacturing a common mode choke coil according to the invention is characterized in that it includes the steps of:

forming the first intermediate opening in an annular shape; and

forming a magnetic member part forming a closed magnetic path in cooperation with the core in the first intermediate opening at the same time when the core is formed.

The method of manufacturing a common mode choke coil according to the invention is characterized in that it includes the steps of:

removing the first intermediate resist layer instead of the step of removing the first intermediate resist layer and the first intermediate electrode film under the first intermediate resist layer;

forming a third intermediate resist layer on the first intermediate electrode film and the first magnetic member layer;

forming the third intermediate resist layer with a third intermediate opening for exposing both ends of the first magnetic member layer;

forming a second magnetic member layer on the first magnetic member layer in the third intermediate opening using a plating process;

forming the core by removing the third intermediate resist layer and the first intermediate electrode film under the same;

forming a third electrode film on the second insulation layer and the second magnetic member layer after forming the first and second helical coil units;

forming a fourth resist layer on the third electrode film;

forming the fourth resist layer with a fourth opening for exposing the third electrode film on the second magnetic member layer;

forming a third magnetic member layer on the third electrode film in the fourth opening using a plating process;

removing the fourth resist layer and the third electrode film under the same;

forming a third insulation layer on which the third magnetic member layer is exposed;

forming a fourth electrode film on the third insulation layer;

forming a fifth resist layer on the fourth electrode film;

forming the fifth resist layer with a fifth opening for exposing the fourth electrode film on the third magnetic member layer on both ends thereof;

forming a fourth magnetic member layer on the fourth electrode film in the fifth opening using a plating process; and

forming a closed magnetic path constituted by the core and the second, third, and fourth magnetic member layers by removing the fifth resist layer and the fourth conductive film under the fifth resist layer.

The method of manufacturing a common mode choke coil according to the invention is characterized in that it includes the steps of:

forming a first intervening resist layer between the second conductive layer and the second electrode film after forming the first insulation layer;

forming the first intervening resist layer with a first intervening opening exposing the first insulation layer and extending across the first conductive layer when the substrate surface is viewed in the normal direction thereof;

forming a groove on the first insulation layer under the first intervening opening;

removing the first intervening resist layer;

forming a first intervening electrode film in the groove and on the first insulation layer;

forming a first magnetic member layer on the first intervening electrode film in the groove using a plating process;

forming a core constituted by the first magnetic member layer and extending through the first and second helical coil units on the side of the inner circumferences thereof; and

forming the second electrode film on the first insulation layer.

The method of manufacturing a common mode choke coil according to the invention is characterized in that it includes the steps of:

forming the first intervening opening in an annular shape; and

forming a magnetic member part forming a closed magnetic path in cooperation with the core in the first intervening opening at the same time when the core is formed.

The method of manufacturing a common mode choke coil according to the invention is characterized in that it includes the steps of:

forming a second intervening resist electrode film on the first insulation layer after forming the first insulation layer;

forming a second intervening resist layer on the second intervening electrode film;

forming the second intervening resist layer with a second intervening opening for exposing the second intervening electrode film on both ends of the core;

forming a second magnetic member layer on the second intervening electrode film in the second intervening opening using a plating process;

removing the second intervening resist layer and the second intervening electrode film under the second intervening resist layer;

forming the second electrode film on the first insulation layer;

forming a second insulation layer for exposing the second magnetic member layer after forming the first and second helical coil units;

forming a third electrode film on the second insulation layer;

forming a fourth resist layer on the third electrode film;

forming the fourth resist layer with a fourth opening exposing the third electrode film on the second magnetic member layer at both ends thereof;

forming a third magnetic member layer on the third electrode film in the fourth opening using a plating process; and

forming a closed magnetic path constituted by the core and the second and third magnetic member layers by removing the fourth resist layer and the third electrode film under the fourth resist layer.

The method of manufacturing a common mode choke coil according to the invention is characterized in that it includes the steps of:

forming an organic insulating material in a gap between the first and second helical coil units; and

heating and curing the organic insulating material to insulate the first and second helical coil units from each other.

The invention makes it possible to manufacture a compact and low-profile common mode choke coil having high electrical characteristics at a low cost.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view of a common mode choke coil 1 according to a first embodiment of the invention;

FIG. 2 is a front view of the common mode choke coil 1 according to the first embodiment of the invention;

FIG. 3 is a side view of the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 4A and 4B show a method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 5A and 5B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 6A and 6B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 7A and 7B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 8A and 8B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 9A and 9B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 10A and 10B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 11A and 11B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 12A and 12B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 13A and 13B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 14A and 14B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 15A and 15B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 16A and 16B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 17A and 17B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 18A and 18B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 19A and 19B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 20A and 20B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 21A and 21B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 22A and 22B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 23A and 23B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 24A and 24B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 25A and 25B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 26A and 26B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 27A and 27B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 28A and 28B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 29A and 29B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 30A and 30B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 31A and 31B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 32A and 32B show the method of manufacturing the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 33A, 33 B, 33 C, and 33 D are plan views of modifications of the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 34A, 34 B, 34 C, and 34 D are plan views of modifications of the common mode choke coil 1 according to the first embodiment of the invention;

FIG. 35 is a perspective view of a modification of the common mode choke coil 1 according to the first embodiment of the invention;

FIGS. 36A and 36B show a method of manufacturing a common mode choke coil 201 according to a second embodiment of the invention;

FIGS. 37A and 37B show the method of manufacturing the common mode choke coil 201 according to the second embodiment of the invention;

FIGS. 38A and 38B show the method of manufacturing the common mode choke coil 201 according to the second embodiment of the invention;

FIGS. 39A and 39B show the method of manufacturing the common mode choke coil 201 according to the second embodiment of the invention;

FIGS. 40A and 40B show the method of manufacturing the common mode choke coil 201 according to the second embodiment of the invention;

FIGS. 41A and 41B show the method of manufacturing the common mode choke coil 201 according to the second embodiment of the invention;

FIGS. 42A and 42B show the method of manufacturing the common mode choke coil 201 according to the second embodiment of the invention;

FIGS. 43A and 43B show the method of manufacturing the common mode choke coil 201 according to the second embodiment of the invention;

FIGS. 44A and 44B show the method of manufacturing the common mode choke coil 201 according to the second embodiment of the invention;

FIGS. 45A and 45B show the method of manufacturing the common mode choke coil 201 according to the second embodiment of the invention;

FIGS. 46A and 46B show the method of manufacturing the common mode choke coil 201 according to the second embodiment of the invention;

FIGS. 47A and 47B show the method of manufacturing the common mode choke coil 201 according to the second embodiment of the invention;

FIGS. 48A and 48B show the method of manufacturing the common mode choke coil 201 according to the second embodiment of the invention;

FIGS. 49A and 49B show the method of manufacturing the common mode choke coil 201 according to the second embodiment of the invention;

FIGS. 50A and 50B show the method of manufacturing the common mode choke coil 201 according to the second embodiment of the invention;

FIGS. 51A and 51B show the method of manufacturing the common mode choke coil 201 according to the second embodiment of the invention;

FIGS. 52A and 52B show the method of manufacturing the common mode choke coil 201 according to the second embodiment of the invention;

FIGS. 53A and 53B show the method of manufacturing the common mode choke coil 201 according to the second embodiment of the invention;

FIGS. 54A and 54B show the method of manufacturing the common mode choke coil 201 according to the second embodiment of the invention;

FIGS. 55A and 55B show the method of manufacturing the common mode choke coil 201 according to the second embodiment of the invention;

FIGS. 56A and 56B show the method of manufacturing the common mode choke coil 201 according to the second embodiment of the invention;

FIGS. 57A and 57B show the method of manufacturing the common mode choke coil 201 according to the second embodiment of the invention;

FIG. 58 is a plan view of a common mode choke coil 401 according to a third embodiment of the invention;

FIG. 59 is a front view of the common mode choke coil 401 according to the third embodiment of the invention;

FIG. 60 is a side view of the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 61A and 61B show a method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 62A and 62B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 63A and 63B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 64A and 64B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 65A and 65B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 66A and 66B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 67A and 67B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 68A and 68B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 69A and 69B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 70A and 70B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 71A and 71B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 72A and 72B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 73A and 73B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 74A and 74B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 75A and 75B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 76A and 76B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 77A and 77B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 78A and 78B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 79A and 79B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 80A and 80B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 81A and 81B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 82A and 82B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 83A and 83B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 84A and 84B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 85A and 85B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 86A and 86B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 87A and 87B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 88A and 88B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 89A and 89B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 90A and 90B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 91A and 91B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 92A and 92B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 93A and 93B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 94A and 94B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 95A and 95B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 96A and 96B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 97A and 97B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 98A and 98B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 99A and 99B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 100A and 100B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 101A and 101B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 102A and 102B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 103A and 103B show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 104A, 104 B, and 104 C show the method of manufacturing the common mode choke coil 401 according to the third embodiment of the invention;

FIGS. 105A and 105B show a method of manufacturing a common mode choke coil 601 according to a fourth embodiment of the invention;

FIGS. 106A and 106B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 107A and 107B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 108A and 108B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 109A and 109B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 110A and 110B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 111A and 111B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 112A and 112B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 113A and 113B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 114A and 114B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 115A and 115B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 116A and 116B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 117A and 117B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 118A and 118B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 119A and 119B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 120A and 120B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 121A and 121B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 122A and 122B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 123A and 123B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 124A and 124B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 125A and 125B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 126A and 126B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 127A and 127B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 128A and 128B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 129A and 129B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 130A and 130B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 131A and 131B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 132A and 132B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 133A and 133B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 134A and 134B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 135A and 135B show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIGS. 136A, 136 B, and 136 C show the method of manufacturing the common mode choke coil 601 according to the fourth embodiment of the invention;

FIG. 137 is a table showing the numbers of thin film manufacturing steps required for common mode choke coils according to the first to fourth embodiments of the invention and the related art;

FIGS. 138A and 138B show a method of manufacturing a common mode choke coil 801 according to a fifth embodiment of the invention;

FIGS. 139A and 139B show the method of manufacturing the common mode choke coil 801 according to the fifth embodiment of the invention;

FIGS. 140A and 140B show the method of manufacturing the common mode choke coil 801 according to the fifth embodiment of the invention;

FIGS. 141A and 141B show the method of manufacturing the common mode choke coil 801 according to the fifth embodiment of the invention;

FIGS. 142A and 142B show the method of manufacturing the common mode choke coil 801 according to the fifth embodiment of the invention;

FIGS. 143A and 143B show the method of manufacturing the common mode choke coil 801 according to the fifth embodiment of the invention;

FIGS. 144A and 144B show the method of manufacturing the common mode choke coil 801 according to the fifth embodiment of the invention;

FIGS. 145A and 145B show the method of manufacturing the common mode choke coil 801 according to the fifth embodiment of the invention;

FIGS. 146A and 146B show the method of manufacturing the common mode choke coil 801 according to the fifth embodiment of the invention;

FIGS. 147A and 147B show the method of manufacturing the common mode choke coil 801 according to the fifth embodiment of the invention;

FIGS. 148A and 148B show the method of manufacturing the common mode choke coil 801 according to the fifth embodiment of the invention;

FIGS. 149A and 149B show the method of manufacturing the common mode choke coil 801 according to the fifth embodiment of the invention;

FIGS. 150A and 150B show the method of manufacturing the common mode choke coil 801 according to the fifth embodiment of the invention;

FIGS. 151A and 151B show the method of manufacturing the common mode choke coil 801 according to the fifth embodiment of the invention;

FIGS. 152A and 152B show the method of manufacturing the common mode choke coil 801 according to the fifth embodiment of the invention;

FIGS. 153A and 153B show the method of manufacturing the common mode choke coil 801 according to the fifth embodiment of the invention;

FIGS. 154A and 154B show the method of manufacturing the common mode choke coil 801 according to the fifth embodiment of the invention;

FIGS. 155A and 155B show the method of manufacturing the common mode choke coil 801 according to the fifth embodiment of the invention;

FIGS. 156A and 156B show the method of manufacturing the common mode choke coil 801 according to the fifth embodiment of the invention;

FIGS. 157A and 157B show the method of manufacturing the common mode choke coil 801 according to the fifth embodiment of the invention;

FIGS. 158A and 158B show the method of manufacturing the common mode choke coil 801 according to the fifth embodiment of the invention;

FIGS. 159A and 159B show the method of manufacturing the common mode choke coil 801 according to the fifth embodiment of the invention;

FIGS. 160A and 160B show the method of manufacturing the common mode choke coil 801 according to the fifth embodiment of the invention; and

FIGS. 161A and 161B show the method of manufacturing the common mode choke coil 801 according to the fifth embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

A common mode choke coil and a method of manufacturing the same according to a first embodiment of the invention will now be described with reference to FIGS. 1 to 35. First, a common mode choke coil 1 according to the present embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a plan view of the common mode choke coil 1 of the present embodiment showing an internal structure of the same. FIG. 2 is a front view of the common mode choke coil 1 taken in the direction indicated by α in FIG. 1 to show the internal structure. For easier understanding, FIG. 2 shows a coil bottom part 31 and a coil top part 35 in one and the same plane, although they are not formed in one and the same plane in practice. FIG. 3 is a side view of the common mode choke coil 1 taken in the direction indicated by β in FIG. 1 to show the internal structure. In FIGS. 1 and 3, hidden outlines are represented by broken lines.

As shown in FIGS. 1 and 3, the common mode choke coil 1 has a general outline in the form of a rectangular parallelepiped provided by forming an insulation layer 60 , a first helical coil unit 11 , a second helical coil unit 12 , and a closed magnetic path 141 on a silicon path 51 made of a single-crystal silicon using a thin-film forming technique.

As shown in FIG. 1, the closed magnetic path 141 has an elongate frame-like shape when viewed in the normal direction of a substrate surface of the silicon path 51 , and it is formed in the insulation layer 60 . The closed magnetic path 141 has a core 41 in the form of a rectangular parallelepiped and a magnetic member part 42 which is in the form of an inverted “C” when viewed in the normal direction of the substrate surface of the silicon substrate 51 .

Each of the first and second helical coil units 11 and 12 is helically (spirally) wound around the core 41 and formed in the insulation layer 60 . The first and second helical coil units 11 and 12 are formed such that their axes of spiral are substantially parallel to the substrate surface of the silicon substrate 51 . The axes of spiral of the first and second helical coil units 11 and 12 substantially coincide with each other.

The first helical coil unit 11 includes one coil having n turns (two turns in FIG. 1), each turn being constituted by a coil bottom part 31 , a coil side part 33 a , a coil top part 35 , and a coil side part 33 b which are each formed, for example, like a rectangular parallelepiped. Similarly, the second helical coil unit 12 includes one coil having n turns, each turn being constituted by a coil bottom part 32 , a coil side part 34 a , a coil top part 36 , and a coil side part 34 b which are each formed, for example, like a rectangular parallelepiped. The coil bottom parts 31 and the coil bottom parts 32 are alternately disposed at equal intervals under the core 41 (on the side of the silicon substrate 51 ), and the coil top parts 35 and the coil top parts 36 are alternately disposed at equal intervals above the core 41 .

In the present application, a term “double spiral structure” is used to refer to a structure in which the coil top parts and the coil bottom parts of the two helical coil units are disposed such that the respective parts alternate with each other and in which the axes of spiral of the helical coil units substantially coincide with each other.

For example, an interval a between one turn of the first helical coil unit 11 and one turn of the second helical coil unit 12 adjacent to the one turn of the coil is in the range from 10 to 50 μm. The first and second helical coil units 11 and 12 are formed from, for example, copper (Cu) to provide the coils with a low resistance. As shown in FIG. 2, one turn of the coil of the first helical coil unit 11 is formed in a rectangular shape when viewed in the direction of the axis of spiral. An internal diameter f of the first helical coil unit 11 in a direction parallel to the substrate surface of the silicon path 51 is, for example, in the range from 5 to 60 μm, and an inner diameter e of the same in a direction perpendicular to the substrate surface is, for example, in the range from 5 to 30 μm. Similarly, one turn of the coil of the second helical coil unit 12 is formed in a rectangular shape. An internal diameter f of the second helical coil unit 12 in the direction parallel to the substrate surface of the silicon path 51 is, for example, in the range from 5 to 60 μm, and an inner diameter e of the same in the direction perpendicular to the substrate surface is, for example, in the range from 5 to 30 μm. The first and second helical coils 11 and 12 are formed to have a section of a constant size in a direction orthogonal to the direction of a current flowing through them.

As shown in FIGS. 1 and 2, the coil bottom parts 31 are formed as a plurality of elongate features whose longer sides have a length c, for example, in the range from 20 to 300 μm and which have a thickness d, for example, in the range from 2 to 10 μm. The coil bottom parts 31 are disposed in parallel on a bottom insulation layer 52 at equal intervals. The coil bottom parts 31 are disposed in parallel at a predetermined angle to the shorter sides of the silicon substrate 51 .

A coil side part 33 a having a height equal to the inner diameter e of the first helical coil unit 11 is formed on one end of a coil bottom part 31 (the left end in FIGS. 1 and 2) in the direction of the longer sides of the same, and a coil side part 33 b having a height substantially equal to that of the coil side part 33 a is formed on another end of the same (the right end in FIGS. 1 and 2).

A plurality of elongate coil top parts 35 having, for example, substantially the same shape as the coil bottom parts 31 (having a length c in the range from 20 to 300 μm along the longer sides thereof and a thickness g in the range from 2 to 10 μm) are disposed in parallel at equal intervals on the coil side parts 33 a and 33 b . As shown in FIG. 1, one end of a coil top part 35 is electrically connected to a coil side part 33 a , and another end of the top coil part 35 is electrically connected to a coil side part 33 b formed on one end of a coil bottom part 31 which extends adjacent to the coil bottom part 31 directly under the above-mentioned coil side part 33 a so as to sandwich a coil bottom part 32 between them.

The coil bottom parts 32 are disposed between the coil bottom parts 31 substantially in parallel with the coil bottom parts 31 . The coil bottom parts 32 are formed from the same material and in the same shape as the coil bottom parts 31 at the same time using the same method of formation. A coil side part 34 a is formed on one end of a coil bottom part 32 (the left end in FIGS. 1 and 2) in the direction of the longer sides of the same, and a coil side part 34 b is formed on another end of the same (the right end in FIGS. 1 and 2). The coil side parts 34 a and 34 b are formed from the same material and in the same shape as the coil side parts 33 a and 33 b at the same time using the same method of formation. The coil side parts 34 a are disposed at equal intervals on a straight line so as to alternate with the coil side parts 33 a , and the coil side parts 34 b are disposed at equal intervals on a straight line so as to alternate with the coil side parts 33 b.

A plurality of elongate coil top parts 36 is disposed in parallel at equal intervals on the coil side parts 34 a and 34 b . The coil top parts 36 are disposed between the coil top parts 35 substantially in parallel with the coil top parts 35 . The coil top parts 36 are formed from the same material and in the same shape as the coil top parts 35 at the same time using the same method of formation. As shown in FIG. 1, one end of a coil top part 36 is electrically connected to a coil side part 34 a , and another end of the top coil part 36 is electrically connected to a coil side part 34 b formed on one end of a coil bottom part 32 which extends adjacent to the coil bottom part 32 directly under the above-mentioned coil side part 34 a so as to sandwich a coil bottom part 31 between them. As shown in FIG. 1, when the substrate surface of the silicon path 51 is viewed in the normal direction thereof, the coil top parts 35 extend across the coil bottom parts 32 at a predetermined angle to them, and the coil top parts 36 extend across the coil bottom parts 31 at a predetermined angle to them.

As shown in FIGS. 1 to 3, the core 41 is disposed to extend through the first and second helical coil units 11 and 12 on the side of the inner circumferences of the coils, the core 41 being in the form of a rectangular parallelepiped having, for example, an overall length b in the range from 100 to 300 μm and a thickness h in the range from 5 to 10 μm. The core 41 is formed to extend substantially coaxially with the axes of spiral of the first and second helical coil units 11 and 12 . The core 41 extends across the coil bottom parts 31 and 32 and the coil top parts 35 and 36 at a predetermined angle to them when the substrate surface of the silicon substrate 51 is viewed in the normal direction thereof. The core 41 is formed from a material having high permeability such as NiFe (permalloy). Since the core 41 is formed from a material having high permeability, the common mode choke coil 1 has a high inductance value, and it can therefore be provided with improved electrical characteristics such as impedance characteristics.

As shown in FIGS. 1 and 2, the magnetic member part 42 , which is formed from the same material as the core 41 to the same thickness h, is connected to both ends of the core 41 . The magnetic member part 42 cooperates with the core 41 to form an annular closed magnetic path 141 . The closed magnetic path 141 is formed substantially in parallel with the surface on which the coil bottom parts 31 are formed. The coil side parts 33 a and 34 a are disposed on the side of the outer circumference of the magnetic path 141 , and the coil side parts 33 b and 34 b are disposed on the side of the inner circumference of the same. Since the closed magnetic path 141 is formed in an annular shape from a material having high permeability, the leakage of magnetic flux can be prevented.

As shown in FIG. 2, the insulation layer 60 is provided by forming the insulation layer (bottom insulation layer) 52 , an insulation layer 54 , an insulation layer 56 , and an insulation layer 58 one over another in the order listed on the silicon substrate 51 . For example, each of the insulation layers 52 , 54 , 56 , and 58 is formed from alumina (Al ₂ O ₃ ). The coil bottom parts 31 and 32 are formed on the insulation layer 52 . The core 41 and the magnetic member part 42 are formed on the insulation layer 54 . The coil top parts 35 and 36 are formed on the insulation layer 56 . As thus described, the common mode choke coil 1 has a multi-layer structure in which the features such as the core 41 and coil bottom parts 31 and insulation layers 52 to 58 are formed one over another.

As shown in FIG. 1, each of two ends of the first helical coil unit 11 is electrically connected to an external electrode connecting part 61 in the form of a rectangular parallelepiped. Similarly, each of two ends of the second helical coil unit 12 is electrically connected to an external electrode connecting part 62 . The external electrode connecting parts 61 and 62 are formed such that they are partially exposed on each of a pair of outer surfaces of the insulation layer 60 opposite to each other. Although not shown, external electrodes are formed on the sides of the common mode choke coil 1 so as to cover the exposed parts of the external electrode connecting parts 61 and 62 . The common mode choke coil 1 is solder-mounted to a printed circuit board (PCB) using the external electrodes.

As described above, in the common mode choke coil 1 of the present embodiment, the first and second helical coil units 11 and 12 are formed such that their axes of spiral are substantially in parallel with the substrate surface of the silicon substrate 51 . Therefore, an increase in the number of turns of the coil results in substantially no change in the thickness of the coil. Further, the closed magnetic path 141 is formed in a plane which is substantially in parallel with the substrate surface of the silicon substrate 51 . Therefore, even if the common mode choke coil 1 has a great number of turns, it can be provided with a profile lower than that of a common mode choke coil whose axis of spiral is oriented perpendicularly to a substrate surface of a silicon path 51 thereof. Since the common mode choke coil 1 has helical coils, the coil 1 can be made smaller than a common mode choke coil having spiral coil extending in one plane even if it has a great number of turns.

The common mode choke coil 1 can be provided with a small profile because it does not have two magnetic substrates disposed opposite to each other unlike common mode choke coils according to the related art.

A method of manufacturing a common mode choke coil 1 according to the present embodiment will now be described with reference to FIGS. 4A to 32B. While a multiplicity of common mode choke coils 1 are simultaneously formed on a wafer, FIGS. 4 A to 32 B show an element forming region of one common mode choke coil 1 . FIGS. 4 to 32 having a suffix A are sectional views taken along lines A-A in FIGS. 4 to 32 having a suffix B. FIGS. 4 to 32 having a suffix B are plan views showing the method of manufacturing a common mode choke coil 1 .

First, as shown in FIGS. 4A and 4B, a film of alumina (Al ₂ O ₃ ) is formed on a silicon path 51 having a thickness of about 0.8 mm formed from a single-crystal silicon using, for example, a sputtering process to provide an insulation layer (bottom insulation layer) 52 having a thickness of about 3 μm. It is not required to form the insulation layer 52 when an insulated substrate having a sufficiently smooth surface is used. Although an organic insulating material may be used to form the insulation layer 52 , alumina is preferred because it can easily form a planar surface compared to an organic insulating material. Each of insulation layers to be described later is formed using the same method as for the insulation layer 52 .

Next, as shown in FIG. 5A, a titanium (Ti) electrode film 71 having a thickness of about 10 nm is formed on the insulation layer 52 using, for example, a sputtering process. The electrode film 71 is used as a buffer film for improving adhesion of a Cu electrode film 72 which will be described later. The buffer film may be formed from other metal materials such as chromium (Cr). Next, as shown in FIGS. 5A and 5B, a Cu electrode film (first electrode film) 72 having a thickness of about 100 nm is formed on the electrode film 71 using, for example, a sputtering process. The electrode film 72 is used as an electrode film for plating the patterns of conductive layers 81 and 82 which will be described later. Each of electrode films to be described later is formed using the same method as for the electrode films 71 and 72 .

Next, a resist is applied to the electrode film 72 using, for example, a spin coat process to form a resist layer (first resist layer) 151 having a thickness in the range from 10 to 15 μm. Each of resist layers to be described later is formed using the same method as for the resist layer 151 . Next, as shown in FIGS. 6A and 6B, the resist layer 151 is patterned to form openings 61 a and 62 a and openings (first openings) 81 a and 82 a for exposing the electrode film 72 in the resist layer 151 . The openings 61 a and 62 a are formed in parallel on each of shorter sides of the element forming region in positions inside and near longer sides of the outer circumference of the region. A plurality of elongate openings 81 a and 82 a are alternately formed in parallel at substantially equal intervals. The openings 81 a and 82 a are formed at a predetermined angle to the shorter sides of the element forming region. The two openings 82 a disposed near the shorter sides are formed such that they are connected to the openings 62 a at one end thereof.

Next, as shown in FIGS. 7A and 7B, Cu electrode layers (first conductive layers) 81 having a thickness in the range from 7 to 10 μm are formed on the electrode film 72 in the openings 61 a and 81 a , and conductive layers (first conductive layers) 82 having the same thickness are formed from the same material on the electrode film 72 in the openings 62 a and 82 a . For example, the conductive layers 81 and 82 are simultaneously formed using a pattern plating process and are each electrically connected to the electrode film 72 under the same. Cu is used to form the conductive layers 81 and 82 in order that first and second helical coil units 11 and 12 to be finally formed will have a low resistance. Each of Cu electrodes to be described later is formed and patterned using the same method as for the conductive layers 81 and 82 . As shown in FIGS. 8A and 8B, the resist layer 151 is then etched away.

Next, a resist is applied throughout the resultant surface to form a resist layer (second resist layer) 153 having a thickness in the range from 15 to 20 μm. Next, as shown in FIGS. 9A and 9B, the resist layer 153 is patterned to form the resist layer 153 with a plurality of openings (second openings) 83 a and 84 a for exposing both ends of the conductive layers 81 and 82 formed in the openings 81 a and 82 a and openings 63 a and 64 a for exposing the conductive layers 81 and 82 formed in the openings 61 a and 62 a . As shown in FIG. 9B, the plurality of openings 83 a and 84 a formed above one end of the plurality of respective conductive layers 81 and 82 are alternately disposed on a straight line at equal intervals, and the plurality of openings 83 a and 84 a formed above another end of the respective layers are alternately disposed on a straight line at equal intervals. Next, as shown in FIGS. 10A and 10B, Cu conductive layers (second conductive layers) 83 having a thickness of about 3 μm are formed on the conductive layers 81 in the openings 63 a and 83 a , and conductive layers (second conductive layers) 84 are formed from the same material with the same thickness on the conductive layers 82 in the openings 64 a and 84 a . The conductive layers 83 and 84 are simultaneously formed using a pattern plating process. Thus, the conductive layers 83 are electrically connected to the conductive layers 81 located under the same, and the conductive layers 84 are electrically connected to the conductive layers 82 located under the same.

Next, as shown in FIGS. 11A and 11B, the resist layer 153 is etched away. As shown in FIGS. 12A and 12B, dry etching (milling) is then performed to remove the electrode film 72 which has been exposed as a result of the removal of the resist layer 153 and to remove the electrode film 71 located under the electrode film 72 . When the electrode films 71 and 72 are removed, the surfaces of the conductive layers 81 to 84 are also etched in an amount substantially equivalent to the thickness of the electrode films 71 and 72 . However, since the conductive layers 81 to 84 are formed sufficiently thick compared to the electrode films 71 and 72 , the layers are not completely removed as a result of the dry etching. Each of electrode films to be described later is removed using the same method as for the electrode films 71 and 72 . Through the above-described steps, coil bottom parts 31 having a multi-layer structure are provided by forming the electrode films 71 and 72 and the conductive layers 81 one over another, and coil bottom parts 32 having a multi-layer structure are provided by forming the electrode films 71 and 72 and the conductive layers 82 one over another. The coil bottom parts 31 and 32 are alternately formed in parallel on the silicon substrate 51 .

Next, as shown in FIGS. 13A and 13B, a film of alumina is formed throughout the resultant surface using a sputtering process to provide an insulation layer (first insulation layer) 54 having a thickness in the range from 10 to 13 μm. As shown in FIGS. 14A and 14B, a CMP (chemical mechanical polishing) process is then performed to polish the surface of the insulation layer 54 until the tops of the conductive layers 83 and 84 are exposed, and a planar surface (CMP surface) 54 a is thereby formed. Visual observation is conducted to check whether the conductive layers 83 and 84 have been exposed or not.

Next, as shown in FIGS. 15A and 15B, a Ti electrode film 91 having a thickness of about 10 nm is formed on the planar surface 54 a of the insulation layer 54 using a sputtering process, and a NiFe (permalloy) electrode film (first intermediate electrode film) 92 having a thickness of about 100 nm is formed on the electrode film 91 using a sputtering process. Like the electrode film 71 , the electrode film 91 is formed as a buffer film for improving the adhesion of the electrode film 92 . The electrode film 92 is used as an electrode film for plating the pattern of a magnetic member layer 101 which will be described later.

A resist is then applied to the electrode film 92 to form a resist layer (first intermediate resist layer) 155 having a thickness in the range from 8 to 13 μm. Next, as shown in FIGS. 16A and 16B, the resist layer 155 is patterned to form an opening (first intermediate opening) 101 a for exposing the electrode film 92 in the resist layer 155 . The opening 101 a is formed like a rectangular window when the element forming region is viewed in the normal direction thereof (the normal direction of the substrate surface of the silicon substrate 51 ), and the opening includes a rectangular opening 41 a and an opening 42 a which is in the form of an inverted “C”. Referring to FIG. 16B, the opening 101 a is formed such that the conductive layers 83 and 84 on the left are disposed on the side of the outer circumference of the opening and such that the conductive layers 83 and 84 on the right are disposed on the side of the inner circumference of the opening. The opening 41 a is disposed between the conductive layers 83 and 84 on both ends of the coil bottom parts 31 and 32 so as to extend across the coil bottom parts 31 and 32 at a predetermined angle to them when the element forming region is viewed in the normal direction thereof.

Next, as shown in FIGS. 17A and 17B, a NiFe magnetic member layer (first magnetic member layer) 101 having a thickness in the range from 5 to 10 μm is formed on the electrode film 92 in the opening 101 a using, for example, a pattern plating process. The magnetic member layer 101 may be formed from a material having high permeability other than NiFe. Next, as shown in FIGS. 18A and 18B, the resist layer 155 is etched away. As shown in FIGS. 19A and 19B, dry etching is then performed to remove the electrode film 92 which has been exposed as a result of the removal of the resist layer 155 and to remove the electrode film 91 located under the electrode film 92 . When the electrode films 91 and 92 are removed, the surface of the magnetic member layer 101 is also etched in an amount substantially equivalent to the thickness of the electrode films 91 and 92 . However, since the magnetic member layer 101 is formed sufficiently thick compared to the electrode films 91 and 92 , the layer is not completely removed as a result of the dry etching. Through the above-described steps, a core 41 having a multi-layer structure is provided in the opening 41 a by forming the electrode films 91 and 92 and the conductive magnetic member layer 101 one over another. A magnetic member part 42 having a multi-layer structure identical to that of the core 41 and forming a closed magnetic path 141 in cooperation with the core 41 is also formed in the opening 42 a.

Next, as shown in FIGS. 20A and 20B, a Ti electrode film 73 having a thickness of about 10 nm is formed throughout the surface using a sputtering process, and a Cu electrode film (second intermediate electrode film) 74 having a thickness of about 100 nm is then formed on the electrode film 73 using a sputtering process. The electrode films 73 and 74 are electrically connected to the conductive layers 83 and 84 located under the same.

Next, a resist is applied to the electrode film 74 to form a resist layer (second intermediate resist layer) 157 having a thickness in the range from 15 to 20 μm. Next, as shown in FIGS. 21A and 21B, the resist layer 157 is patterned to form the resist layer 157 with openings (second intermediate openings) 85 a and 86 a for exposing the electrode film 74 on the conductive layers 83 and 84 formed in the openings 83 a and 84 a and openings 65 a and 66 a for exposing the electrode film 74 on the conductive layers 83 and 84 formed in the openings 63 a and 64 a.

Next, as shown in FIGS. 22A and 22B, Cu conductive layers (first intermediate conductive layers) 85 having a thickness in the range from 7 to 15 μm are formed on the electrode film 74 in the openings 65 a and 85 a , and conductive layers (first intermediate conductive layers) 86 are formed from the same material with the same thickness on the electrode film 74 in the openings 66 a and 86 a . The conductive layers 85 and 86 are formed using a pattern plating process and are each electrically connected to the electrode film 74 located under the same. Next, as shown in FIGS. 23A and 23B, the resist layer 157 is etched away. As shown in FIGS. 24A and 24B, dry etching is then performed to remove the electrode film 74 exposed as a result of the removal of the resist layer 157 and to remove the electrode film 73 under the electrode film 74 . Through the above-described steps, coil side parts 33 a and 33 b having a multi-layer structure are provided by forming the conductive layers 83 , the electrode films 73 and 74 , and the conductive layers 85 one over another, and coil side parts 34 a and 34 b having a multi-layer structure are provided by forming the conductive layers 84 , the electrode films 73 and 74 , and the conductive layers 86 one over another. Referring to FIG. 24B, the coil side parts 33 a and 34 a are alternately disposed on the left side to align on a straight line at equal intervals, and the coil side parts 33 b and 34 b are alternately disposed on the right side to align on a straight line at equal intervals.

Next, as shown in FIGS. 25A and 25B, a film of alumina is formed throughout the resultant surface using a sputtering process to provide an insulation layer (second insulation layer) 56 having a thickness in the range from 7 to 15 μm. As shown in FIGS. 26A and 26B, a CMP process is then performed to polish the surface of the insulation layer 56 until the tops of the conductive layers 85 and 86 is exposed, and a planar surface 56 a is thereby formed. In doing so, the insulation layer 56 is not polished until the core 41 and the magnetic member part 42 are exposed.

Next, as shown in FIGS. 27A and 27B, a Ti electrode film 75 having a thickness of about 10 nm is formed on the planar surface 56 a of the insulation layer 56 using a sputtering process, and a Cu electrode film (second electrode film) 76 having a thickness of about 100 nm is formed on the electrode film 75 using a sputtering process. The electrode films 75 and 76 are electrically connected to the conductive layers 83 through the electrode films 73 and 74 and the conductive layers 85 and are electrically connected to the conductive layers 84 through the electrode films 73 and 74 and the conductive layers 86 .

A resist is then applied to the electrode film 76 to form a resist layer (third resist layer) 159 having a thickness in the range from 10 to 15 μm. Next, as shown in FIGS. 28A and 28B, the resist layer 159 is patterned to form a plurality of openings (third openings) 87 a and 88 a for exposing the electrode film 76 in the form of elongate strips and to form openings 67 a and 68 a for exposing the electrode film 76 on the conductive layers 85 and 86 formed in the openings 65 a and 66 a . As a result, when the element forming region is viewed in the normal direction thereof, the openings 87 a and the openings 88 a are alternately formed in parallel at substantially equal intervals, each opening 87 a exposing the electrode film 76 on a coil side part 33 a at one end thereof and exposing, at another end thereof, the electrode film 76 on the coil side part 33 b on a coil bottom part 31 extending adjacent to the coil bottom part 31 directly under the above-mentioned coil side 33 a so as to sandwich a coil bottom part 32 between them, each opening 88 a exposing the electrode film 76 on a coil side part 34 a at one end thereof and exposing, at another end thereof, the electrode film 76 on the coil side part 34 b on a coil bottom part 32 extending adjacent to the coil bottom part 32 directly under the above-mentioned coil side part 34 a so as to sandwich a coil bottom part 31 between them. The openings 87 a are formed to extend across the coil bottom parts 32 and to face the bottom parts with the core 41 sandwiched between them when the element forming region is viewed in the normal direction thereof. The openings 88 a are formed to extend across the coil bottom parts 31 and to face the bottom parts 31 with the core 41 sandwiched between them, when viewed in the same direction. The openings 87 a disposed near the shorter sides of the element forming region are formed in connection with the respective openings 67 a at one end thereof.

Next, as shown in FIGS. 29A and 29B, Cu conductive layers (third conductive layers) 87 having a thickness in the range from 7 to 10 μm are formed on the electrode film 76 in the openings 67 a and 87 a , and conductive layers (third conductive layers) 88 are formed from the same material to the same thickness on the electrode film 76 in the openings 68 a and 88 a . The conductive layers 87 and 88 are simultaneously formed using a pattern plating process and are each electrically connected to the electrode film 76 under the same. Next, as shown in FIGS. 30A and 30B, the resist layer 159 is etched away. Next, as shown in FIGS. 31A and 31B, the electrode film 76 which has been exposed as a result of the removal of the resist layer 159 and the electrode film 75 under the electrode film 76 are removed. Thus, coil top parts 35 having a multi-layer structure are provided by forming the electrode films 75 and 76 and the conductive layers 87 one over another, and coil top parts 36 having a multi-layer structure are provided by forming the electrode films 75 and 76 and the conductive layers 88 one over another.

Through the above-described steps, a first helical coil unit 11 is formed, which includes one coil having n turns each constituted by a coil bottom part 31 , a coil side part 33 a , a coil top part 35 , and a coil side part 33 b . At the same time, a second helical coil unit 12 is formed, which includes one coil having n turns each constituted by a coil bottom part 32 , a coil side part 34 a , a coil top part 36 , and a coil side part 34 b . The first and second helical coil units 11 and 12 are formed in a double spiral structure. External electrode connecting parts 61 having a multi-layer structure constituted by the conductive layers 81 , 83 , 85 , and 87 are simultaneously formed in the openings 61 a , 63 a , 65 a , and 67 a , and external electrode connecting parts 62 having a multi-layer structure constituted by the conductive layers 82 , 84 , 86 , and 88 are simultaneously formed in the openings 62 a , 64 a , 66 a , and 68 a.

The coil top parts 35 and 36 are alternately disposed in parallel. When the element forming region is viewed in the normal direction thereof, the coil top parts 35 are disposed to extend across the coil bottom parts 32 with the core 41 sandwiched between them, and the coil top parts 36 are disposed to extend across the coil bottom parts 31 with the core 41 sandwiched between them.

Next, as shown in FIGS. 32A and 32B, a film of alumina is formed throughout the surface using a sputtering process to provide an insulation layer 58 having a thickness of about 10 μm which is to serve as a protective film for the coil top parts 35 and 36 . Referring to the material to form the insulation layer 58 , an insulating material other than alumina may be used. Through the above-described steps, an insulation layer 60 having a multi-layer structure is provided by forming the insulation layers 52 , 54 , 56 , and 58 one over another. The first and second helical coil units 11 and 12 and the closed magnetic path 141 are enclosed in the insulation layer 60 .

Next, the silicon path 51 is ground from the bottom thereof to achieve a desired thickness or to remove the substrate completely. The wafer is then cut along predetermined cutting lines to divide a plurality of the common mode choke coils 1 formed on the wafer into each element forming region in the form of a chip. The external electrode connecting parts 61 and 62 are partially exposed on an outer surface of the insulation layer 60 . Although not shown, external electrodes are then formed in electrical connection with the external electrode connecting parts 61 and 62 . Next, chamfering is performed on corners of the chip to complete a common mode choke coil 1 .

As described above, according to the method of manufacturing the common mode choke coil 1 of the present embodiment, the first and second helical coil units 11 and 12 having axes of spiral substantially in parallel with the substrate surface and the core 41 and the magnetic member part 42 forming the closed magnetic path 141 can be formed at a series of manufacturing steps using thin film formation techniques. Therefore, the common mode choke coil 1 can be provided at a low cost through a reduction in the number of manufacturing steps.

In the present embodiment, the closed magnetic path 141 can be formed at the same time when a thin film forming step is performed to form the first and second helical coil units 11 and 12 , the external electrode connecting parts 61 and 62 , and the insulation layer 60 . Therefore, there is no need for a substrate combining step for combining a magnetic substrate with the coil by bonding it using a bonding layer formed on the insulation layer. Manufacturing steps for the common mode choke coil 1 can therefore be simpler than those for common mode choke coils according to the related art. Since the manufacturing cost can be thus reduced, the common mode choke coil 1 can be provided at a low cost.

A common mode choke coil according to a modification of the present embodiment will now be described with reference to FIGS. 33A to 35. Common mode choke coils 1 ′ to 8 according to Modifications 1 to 8 are formed using the same manufacturing method as for the common mode choke coil 1 according to the present embodiment, and they have a general outline in the form of a rectangular parallelepiped. The common mode choke coils 1 ′ to 8 include first and second helical coil units having axes of spiral substantially in parallel with a substrate surface (element forming surface) of a silicon substrate 51 . Further, a core forming a part of a closed magnetic path is disposed on the side of the inner circumferences of the first and second coil units so as to extend through the coils. The closed magnetic path is formed in a plane in parallel with the element forming surface. In the following description, elements having functions and effects like those of elements in the first embodiment are indicated by like reference numerals and will not be described in detail.

First, a common mode choke coil 1 ′ according to Modification 1 of the present embodiment will be described with reference to FIG. 33A. FIG. 33A is a plan view of the common mode choke coil 1 ′ of the present modification showing an internal structure of the same. The common mode choke coil 1 ′ of the present modification is identical in configuration to the common mode choke coil 1 of the first embodiment except for the number of turns of the coils and the shape of external electrode connecting parts 63 and 64 .

A pair of external electrode connecting parts 63 and 64 is formed in parallel on each of short sides of the outer circumference of the common mode choke coil 1 ′. The external electrode connecting parts 61 and 62 of the common mode choke coil 1 shown in FIG. 1 are formed in a rectangular shape whose longitudinal direction extends along the longer sides of the coil 1 constituting the outer circumstance thereof. On the contrary, the external electrode connecting parts 63 and 64 of the common mode choke coil 1 ′ of the present modification are formed in a rectangular shape whose longitudinal direction extends along the shorter sides of the outer circumference of the coil 1 ′. Both ends of the first helical coil unit 11 are electrically connected to the pair of external electrode connecting parts 63 respectively, and both ends of the second helical coil unit 12 are electrically connected to the pair of external electrode connecting parts 64 respectively. In common mode choke coils 2 to 5 to be described later, external electrode connecting parts 63 are similarly electrically connected to both ends of a first helical coil unit respectively, and external electrode connecting parts 64 are similarly electrically connected to both ends of a second helical coil unit respectively.

Table 1 shows four examples of configuration patterns of the common mode choke coil 1 which are different from each other in any of the coil pitch (represented by p) of the first and second helical coil units 11 and 12 , the coil width on a section orthogonal to the direction in which a current flows through the coil, the number n of turns of the coil, the coil inner diameter (represented by f), and the width of the core 41 (represented by w). In Table 1, “14×2” means that each of the first and second helical coil units 11 and 12 has 14 turns.

	TABLE 1
	Pattern	Pattern	Pattern	Pattern
	1	2	3	4
Coil Pitch p (μm)	20	25	20	25
Coil Width (μm)	10	10	10	10
Number of Turns n	14 × 2	12 × 2	14 × 2	12 × 2
Coil Inner Diameter f (μm)	240	240	240	240
Core Width w (μm)	150	150	200	200

A common mode choke coil 2 according to Modification 2 of the present embodiment will now be described with reference to FIG. 33B. FIG. 33B is a plan view of the common mode choke coil 2 of the present modification showing an internal structure of the same. As shown in FIG. 33B, the common mode choke coil 2 of the present modification is characterized in that it includes two cores 43 a and 43 b which constitute an element of a closed magnetic path 143 by extending longitudinally of the closed magnetic path 143 that is in the form of a ring having a rectangular circumference so as to sandwich the hollow of the ring and first and second helical coil units 13 and 14 which are wound around the cores 43 a and 43 b , respectively. The closed magnetic path 143 is symmetric about an imaginary straight line passing through the center of the hollow and extending in parallel with the longitudinal direction of an element forming region. The first helical coil unit 13 is wound around the core 43 a , and the second helical coil unit 14 is wound around the core 43 b . The first and second helical coil units 13 and 14 have a spiral structure similar to that of the first helical coil unit 11 . Table 2 shows two examples of configuration patterns of the common mode choke coil 2 .

	TABLE 2
	Pattern 5	Pattern 6
	Coil Pitch p (μm)	20	25
	Coil Width (μm)	10	10
	Number of Turns n	14 × 2	12 × 2
	Coil Inner Diameter f (μm)	190	190
	Core Width w (μm)	100	100

A common mode choke coil 3 according to Modification 3 of the present embodiment will now be described with reference to FIG. 33C. FIG. 33C is a plan view of the common mode choke coil 3 of the present modification showing an internal structure of the same. As shown in FIG. 33C, the common mode choke coil 3 of the present modification is characterized in that first and second helical coil units 15 and 16 are wound around a core 41 separately from each other. Referring to FIG. 33C, the first helical coil unit 15 is disposed on the upper side of the core, and the second helical coil unit 16 is disposed on the lower side.

The angle at which coil top parts 35 and 36 and coil bottom parts 31 and 32 of the common mode choke coil 3 extend across the extending direction of the core 41 can be made closer to 90 deg when compared to such angles in the common mode choke coils 1 , 1 ′, and 2 . Since the core 41 is therefore more efficiently magnetized by magnetic fields generated by the first and second helical coil units 15 and 16 , the common mode choke coil 3 can be provided with higher electrical characteristics. Table 3 shows two examples of configuration patterns of the common mode choke coil 3 .

	TABLE 3
	Pattern 7	Pattern 8
	Coil Pitch p (μm)	20	25
	Coil Width (μm)	10	10
	Number of Turns n	14 × 2	12 × 2
	Coil Inner Diameter f (μm)	240	240
	Core Width w (μm)	150	150

A common mode choke coil 4 according to Modification 4 of the present embodiment will now be described with reference to FIG. 33D. FIG. 33D is a plan view of the common mode choke coil 4 of the present modification showing an internal structure of the same. As shown in FIG. 33D, the common mode choke coil 4 of the present modification is characterized as follows. The coil includes first and second helical coil units 17 and 18 having a double spiral structure. One turn of the coil of the first helical coil unit 17 is constituted by a coil bottom part 31 a , a coil side part (not shown), a coil top part 35 a , and another coil side part (not shown), and a first imaginary plane IP 1 including the coil top part 35 a and the two coil side parts among those elements is orthogonal to the core 41 . One turn of the coil of the second helical coil unit 18 is constituted by a coil bottom part 32 a , a coil side part (not shown), a coil top part 36 a , and another coil side part (not shown), and a second imaginary plane IP 2 including the coil top part 36 a and the two coil side parts among those elements is orthogonal to the core 41 . The first imaginary plane IP 1 and the second imaginary plane IP 2 do not cross each other.

The axes of spiral of the first and second helical coil units 17 and 18 substantially coincide with the extending direction of the core 41 . While the coil top parts 35 a are orthogonal to the core 41 , the coil bottom parts 31 a extend across the core 41 at a predetermined angle to the same. Adjoining coil top parts 35 a are electrically connected to each other by the coil bottom parts 31 a through a coil side part. Similarly, the coil bottom parts 32 a extend across the core 41 at a predetermined angle to the same, and adjoining coil top parts 36 a are electrically connected to each other by the coil bottom parts 32 a through a coil side part. In the first and second helical coil units 17 and 18 of the present modification, two coil side parts and a coil top part are included in an imaginary plane orthogonal to the core. Alternatively, those units may be formed such that two coil side parts and a coil bottom part are included in such an imaginary plane.

In the common mode choke coil 4 , since each of the first and second imaginary planes IP 1 and IP 2 is orthogonal to the core 41 , the core 41 can be more efficiently magnetized than in the common mode choke coil 3 of Modification 3 , and further improvement of electrical characteristics can be achieved. Since the first and second helical coil units 17 and 18 form a double spiral structure without being separated from each other, the common mode choke coil 4 can sufficiently eliminate common mode noise signals. Table 4 shows t