JP3128825B2 - High frequency coil - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency coil,
In particular, the present invention relates to a chip-type high-frequency coil used for a microwave circuit or the like.

[0002]

2. Description of the Related Art As a prior art of this kind, there is a chip type coil adopted in a high frequency microwave circuit and the like proposed by the present applicant in Japanese Patent Application Laid-Open No. 2-54903. This chip-type coil has a pair of terminal electrodes formed on the surface of a substrate, a strip-shaped coil conductor connected to both ends of the terminal electrode, and a polyimide or polyamide covering the surface of the terminal electrode and the coil conductor. In addition, an insulating film made of is formed, and at least a terminal electrode portion of the insulating film is removed by an etching method to expose the terminal electrode.

[0003]

In this chip type coil, magnetic flux leaks to the outside, and since the coil conductor is formed by using a thin film technique, the conductor resistance is large.
Q was low. Furthermore, when such a chip-type coil is formed using a conventional magnetic substrate, there is a problem that the upper limit of the usable frequency is limited to about 200 MHz.

[0004] Therefore, a main object of the present invention is to provide a high-frequency coil which has a large shielding effect, can improve Q, and can further expand a usable frequency band.

[0005]

According to the present invention, there is provided a magnetic substrate having a high magnetic permeability, a first insulating film formed on the magnetic substrate,
A thin-film coil conductor formed on the first insulating film with a space between the lines; a pair of terminal electrodes on the first insulating film spaced apart from the coil conductor and partially connected to the coil conductor; A second insulating film formed so as to cover the surface of the conductor and expose the terminal electrode; and a magnetic resin film formed on the second insulating film, wherein the first and second insulating films are made of polyimide. This is a high-frequency coil formed of a resin or a polyamide resin, and further formed with a magnetic resin film reaching the magnetic substrate between the coil conductors and between the terminal electrode and the coil conductor.

[0006]

The coil conductor is formed on the magnetic substrate via the first insulating film, and the upper portion of the coil conductor is covered with a resin (magnetic resin film) containing a magnetic material. Therefore, the coil conductor is covered with the magnetic substrate and the magnetic resin film. Further, since the magnetic resin film is inserted between the wires of the strip-shaped coil conductor, a magnetic path surrounded by the magnetic substrate and the magnetic resin film is formed. Therefore, leakage of the magnetic flux to the outside can be effectively prevented. An insulating film (first and second insulating films) made of a polyimide resin (or polyamide resin) having a low dielectric constant and excellent in smoothness and workability is provided between the magnetic substrate and the coil conductor and between the coil conductors. By forming and covering the coil conductor with a magnetic material, the stray capacitance between wires can be eliminated, and the adhesion with the magnetic material resin film can be strengthened.

[0007]

According to the present invention, since the coil conductor is covered with the magnetic material, there is no leakage of magnetic flux, and the shielding effect is enhanced. In addition, by using a magnetic substrate having a high magnetic permeability, the inductance of the coil conductor is improved, and when obtaining the same inductance, the wire length of the coil conductor can be shortened, and Q is improved. 2
It can be used in a high frequency band of 00 MHz or more.
Furthermore, since the coil conductor is coated with a polyimide resin or a polyamide resin having excellent smoothness, the magnetic flux that cancels out between lines is reduced, and a coil having a small deviation and a large inductance can be obtained.

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, a high frequency coil 10 as a background of the present invention is configured as a chip type coil and includes a magnetic substrate 12 having a high magnetic permeability capable of coping with a high frequency. Both ends of the upper surface of the magnetic substrate 12 are connected to the terminal electrodes 14a and 14b.
Is formed, and a spiral coil conductor 16 is formed in the center of the upper surface of the magnetic substrate 12. The outer end 16a of the coil conductor 16 is connected to the terminal electrode 14 as shown in FIG.
a. The terminal electrodes 14a and 14b and the coil conductor 16 are formed by forming an Ag conductor film on the entire upper surface of the magnetic substrate 12 by a thin film forming technique such as evaporation, sputtering, or ion plating.
The coil conductor 16 is formed by removing portions other than 4a, 14b and the coil conductor 16 by etching. The coil conductor 16 is formed to have a width of approximately 40 μm and a thickness of 5 μm, for example.

The entire surface of the upper surface of the magnetic substrate 12 is
An insulating film 18 made of a resin such as polyimide or polyamide is coated so as to cover the terminal electrodes 14a and 14b and the coil conductor 16. In the insulating film 18, the terminal electrodes 14a and 14b are removed by etching, and the inner end 16b of the coil conductor 16 is also removed by etching, so that a through hole 20 is formed.

A lead conductor 22 extending from the through hole 20 to the terminal electrode 14b is formed on the upper surface of the insulating film 18, and the lead conductor 22 is formed by the same method as the above-described coil conductor 16. Thus, the inner end 16b of the coil conductor 16 is connected to one end of the lead conductor 22 formed in the through hole 20, and is connected to the terminal electrode 14b via the lead conductor 22.

Further, on the entire upper surface of the magnetic substrate 12,
A protective insulating film 24 for protecting the surface is coated, and the terminal electrodes 14a and 14b of the protective insulating film 24 are removed by etching. Then, a paste-like resin 26 containing a magnetic material is formed on the entire upper surface of the protective insulating film 24. Such a high-frequency coil 10 is shown in FIGS.
It is manufactured in the order of steps shown in FIG.

First, a magnetic substrate 12 is prepared as shown in FIG. After mirror-polishing the upper surface of the magnetic substrate 12, the magnetic substrate 12 is washed. Then, the magnetic substrate 1
The coil conductor 16 and the terminal electrodes 14a and 14b are formed on the upper surface of 2, for example, by photolithography. First, as shown in FIG. 4, a conductor film 28 having a two-layer structure is formed on the upper surface of the magnetic substrate 12. That is, a titanium film or a nichrome film 28a for improving adhesion is formed on the upper surface of the magnetic substrate 12 by, for example, sputtering, and an Ag film having good conductivity is further formed on the upper surface of the titanium film or the nichrome film 28a. 28b is formed by sputtering, for example, to form a conductor film 28b.
Is formed.

Next, as shown in FIG. 5, a resist film 30 is coated on the upper surface of the conductor film 28. The resist film 30 is formed in advance by the coil conductor 16 and the terminal electrode 14.
a, which is covered with a mask designed according to 14b.
This is subjected to a developing treatment to remove unnecessary portions of the resist film 30, thereby obtaining a desired resist film 30 shown in FIG. And
When the upper surface of the magnetic substrate 12 is etched, the portion of the conductor film 28 where the resist film 30 is not formed is removed,
The coil conductor 16 and the terminal electrodes 14a and 14b are formed. After that, the resist film 30 is removed by, for example, a thinner or the like, to obtain a state shown in FIG.

Further, an insulating film 18 is formed on the upper surface of the magnetic substrate 12 by, for example, photolithography. First, as shown in FIG. 7, the coil conductor 16 and the terminal electrodes 14a, 14b
Is coated with an insulating film 18 made of, for example, polyimide or polyamide, and dried.

The terminal electrodes 14a, 1 of the insulating film 18 are
The portion other than the portion 4b and the inner end 16b of the coil conductor 16 is exposed. Next, when this is developed (etched), only the exposed portion remains. That is, as shown in FIG. 8, while the terminal electrodes 14a and 14b are exposed,
The through hole 20 is formed, and the inner end 1 of the coil conductor 16 is formed.
The portion 6b is exposed. Next, this is heated to approximately 400 ° C. in a nitrogen gas atmosphere to cure the insulating film 18. In addition, when polyimide is used for the insulating film 18 and the polyimide is non-photosensitive, after applying a positive resist,
The remaining portion of the insulating film 18 may be exposed and developed.

After a conductor layer is formed on the surface of the insulating film 18 by, for example, sputtering, the lead is formed as shown in FIG. 9 in the same manner as the above-described method of forming the coil conductor 16 and the terminal electrodes 14a and 14b. The conductor 22 is formed. One end of the lead conductor 22 is connected to the inner end 16b of the coil conductor 16 via the through hole 20, and the other end is connected to the end electrode 14b. Then, as shown in FIG. 10, the entire upper surface of the magnetic substrate 12 is coated with a protective insulating film 24 made of, for example, polyimide or polyamide, and as shown in FIG.
And 14b are etched in the same manner as the insulating film 18. Then, a resin 26 containing a magnetic material is formed on the entire upper surface of the protective insulating film 24, and the chip-shaped high-frequency coil 10 shown in FIG. 1 is formed.

In the high-frequency coil 10 formed as described above, the coil conductor 16 is formed on the magnetic substrate 12, and the resin 26 containing the magnetic material is
Is formed, the coil conductor 16 is covered with the magnetic substrate 12 and the resin 26. And the high-frequency coil 10 itself can be reduced in size.

The coil conductor 16 can be applied not only to the above-mentioned spiral conductor but also to a conductor having a meander type coil conductor 30 formed on a magnetic substrate 12 as shown in FIG. . And FIG.
3 and the high-frequency coil 40 of this embodiment shown in FIG.
Is to insert not only the upper surface of the coil conductor 50 but also the paste-like resin (magnetic resin film) 42 mixed with the magnetic material into the space between the coil conductors 50, and further, the outer end of the resin 42 is By connecting to the substrate 44, the shielding effect is further enhanced.

Since the high-frequency coil 40 is manufactured through, for example, photolithography through substantially the same steps as in the previous embodiment, the manufacturing steps of the high-frequency coil 40 will be briefly described here. 14, 16, 1
8, FIG. 20 and FIG. 22 show the dashed line A in FIG.
It is an end elevation which shows the end surface cut | disconnected in -A.

First, as shown in FIGS. 15 and 16,
A magnetic substrate 44 having a high magnetic permeability capable of coping with a high frequency is prepared, and an upper surface of the magnetic substrate 44 is coated with an insulating film 46 having a predetermined shape made of a resin such as polyimide or polyamide. Then, a conductor film is formed on the entire upper surface of the magnetic substrate 44 by, for example, sputtering, and unnecessary portions are removed by etching. As shown in FIGS. 17 and 18, a coil pattern is formed on the insulating film 46. I do. That is, the terminal electrodes 48a and 48b are formed at both ends of the magnetic substrate 44, and the coil conductor 50 is formed at the center of the magnetic substrate 44, respectively.
0a is connected to the terminal electrode 48b. Then, as shown in FIGS. 19 and 20, first, an insulating film 52 made of a resin such as polyimide or polyamide is connected so that the inner end 50b of the coil conductor 50 can be connected to the terminal electrode 48a.
Is formed so as to cover a part of the coil conductor 50. Then, a conductive film is formed on the insulating film 52 by, for example, sputtering or the like, and is etched to remove unnecessary portions.
A conductor film connecting the inner end of the coil conductor and the terminal electrode is formed.

Next, as shown in FIGS. 21 and 22, an insulating film 56 made of a resin such as polyimide or polyamide is formed on the upper surface of the magnetic substrate 44 so as to cover the coil conductor 50 and part of the terminal electrodes 48a and 48b. Coating. Then, as shown in FIGS. 13 and 14, not only the upper part of the coil conductor 50 but also the central part 58 and the outer peripheral part 60 of the coil conductor 50 are coated with the resin 42 mixed with a magnetic substance.

In the high-frequency coil 40 formed as described above, as shown in FIG. 14, the coil conductor 50 is covered with the magnetic substrate 44 and the resin 42, and the magnetic path 62 is formed by the magnetic substrate 44 and the resin 42. Since it is formed, the magnetic flux does not leak out, and the shielding effect is further enhanced. Therefore, while the inductance is further improved, the wire length of the coil conductor 50 at the same inductance can be shortened, and Q is further improved. Further, the high-frequency coil 40 itself can be further miniaturized, and can be used in a high-frequency band of 200 MHz or more.

[Brief description of the drawings]

FIG. 1 is an end view showing an embodiment as a background of the present invention.

FIG. 2 is a plan view showing a state where a coil conductor and terminal electrodes are formed on a magnetic substrate.

FIG. 3 is an end view showing a state where a magnetic substrate is prepared.

FIG. 4 is an end view showing a state where a conductor film is formed.

FIG. 5 is an end view showing a state where a resist is formed.

FIG. 6 is an end view showing a state where a coil conductor and a terminal electrode are formed by etching.

FIG. 7 is an end view showing a state where an insulating film is formed.

FIG. 8 is an end view showing a state where an insulating film is etched.

FIG. 9 is an end view showing a state where a lead conductor is formed.

FIG. 10 is an end view showing a state where a protective insulating film is formed.

FIG. 11 is an end view showing a state where a protective insulating film is etched.

FIG. 12 is a perspective view showing a magnetic substrate on which another coil conductor is formed.

FIG. 13 is a plan view of the embodiment of FIG. 14;

FIG. 14 is an end view showing one embodiment of the present invention.

FIG. 15 is a plan view showing a state where an insulating resin is formed on an upper surface of a magnetic substrate.

FIG. 16 is an end view showing a state where an insulating resin is formed on an upper surface of a magnetic substrate.

FIG. 17 is a plan view showing a state where a conductor film and terminal electrodes are formed.

FIG. 18 is an end view showing a state where a conductor film and a terminal electrode are formed.

FIG. 19 is a plan view showing a state where an inner end of a coil conductor and a terminal electrode are connected.

FIG. 20 is an end view showing a state where an inner end of the coil conductor is connected to a terminal electrode.

FIG. 21 is a plan view showing a state where an insulating film is formed.

FIG. 22 is an end view showing a state where an insulating film is formed.

[Explanation of symbols]

10, 40 high-frequency coil 12, 44 magnetic substrate 14a, 14b, 48a, 48b terminal electrode 16, 50 coil conductor 18, 46, 52, 56 insulating film 24 protective insulating film 26, 42 magnetic material Mixed resin

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-50410 (JP, A) JP-A-63-283004 (JP, A) JP-A-2-123706 (JP, A) 68621 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01F 17/00 H01F 27/28-27/29

Claims (1)

(57) [Claims] A magnetic substrate having a high magnetic permeability; a first insulating film formed on the magnetic substrate; a thin-film coil conductor formed on the first insulating film with a space between the lines; A pair of terminal electrodes that are spaced apart from and partially connected to the coil conductor on the first insulating film, and are formed so as to cover the surface of the coil conductor and expose the terminal electrodes; A second insulating film; and a magnetic resin film formed on the second insulating film; wherein the first and second insulating films are formed of a polyimide resin or a polyamide resin; A high-frequency coil in which a resin film is formed so as to reach the magnetic substrate at the line interval of the coil conductor and at the interval between the terminal electrode and the coil conductor.