JP2012023661A - Plane antenna and manufacturing method thereof - Google Patents

Abstract

A high-frequency planar antenna that is stable and has low radio wave loss and a method for manufacturing the same are provided.
A planar antenna according to the present invention includes a substrate 1 made of a dielectric, a predetermined pattern (3, 4) formed on the substrate 1, and a substrate 1 other than the predetermined pattern (3,4). The conductor film 2 includes at least a first conductor film and a second conductor film, and the first conductor film is formed on the substrate 1 by a sputtering method. The second conductor film is formed by plating on the first conductor film, and the film thickness d ₁ of the first conductor film satisfies the requirement of the following formula (1).
d ₁ ≧ (2 / σ ₁ ωμ ₁ ) ^1/2 (1)
In Equation (1), ω = 2πf, σ ₁ is the conductivity of the first conductor film, f is the frequency of the high-frequency signal to be used, and μ ₁ is the magnetic permeability of the first conductor film. .
[Selection] Figure 1

Description

  The present invention relates to a planar antenna and a method for manufacturing the same, and more particularly to a planar antenna for forming a conductor film in contact with the surface of a substrate by a sputtering method and a method for manufacturing the same.

  In recent years, communication systems using radio have been widely used against the background of highly information-oriented society, and the development of communication systems using microwave and millimeter wave regions with a large amount of information is particularly remarkable. In such a communication system, the planar antenna is suitable as an input / output device for a short-wavelength wireless system.

  By the way, it is necessary to make the size of the antenna in accordance with the size of the wavelength of the electric (magnetic) wave, and when the wavelength is shortened, the shape of the antenna as the input / output device needs to be miniaturized. As a result, in recent antennas, a fine processing technique is required for the dimensional accuracy of the antenna. Conventionally, antennas such as slot patterns and patch patterns have been formed using etching technology. However, microfabrication has a large effect on antenna characteristics, and the conventional etching technology has the disadvantage that it cannot produce large amounts of antennas with high accuracy. there were. In particular, dimensional accuracy in millimeter waves is required to be at least 1% of the wavelength. For example, when the frequency is 50 GHz, dimensional accuracy of several tens of μm is required. It is conceivable to apply a microfabrication technique applicable to the LSI (Large Scale Integration) manufacturing process for such a request, but such a technique cannot manufacture an inexpensive antenna.

  Therefore, in Patent Document 1, for example, a predetermined pattern, which is a region not covering the conductor on the substrate, and the substrate are integrally formed by an injection molding method, so that the slot of the planar antenna having the predetermined pattern can be formed with high dimensional accuracy. A method of forming has been proposed. Manufacturing a substrate having a predetermined pattern by an injection molding method makes it easy to mass-produce the antenna once the substrate mold having the predetermined pattern is formed, and the antenna can be formed at low cost. In addition, the injection molding method can mold a predetermined pattern in units of microns, and can provide a small antenna suitable for shortening the wavelength.

  On the other hand, in the planar antenna, the thickness of the conductor film is determined in consideration of the electromagnetic skin effect at the operating frequency. The skin effect is a phenomenon in which the current density flowing through the conductor film flows more concentrated on the surface of the conductor as the frequency increases, and the resistance value at high frequencies does not decrease because the total film thickness of the conductor film is thicker. Absent. If the thickness of the conductor film is about 10 times the skin depth, which is the thickness at which the current density is 1 / e (0.37 times) the value of the current density on the conductor surface, the influence of the skin effect is eliminated. it can. Note that the value of the skin depth decreases in inverse proportion to the square root of the frequency. At 50 GHz, the skin resistance is reduced by setting the thickness of the conductor film to, for example, about 3 μm. And as a conductor film, the one where electrical conductivity is higher is preferable since conductor loss decreases. Therefore, the conductivity is increased by forming the conductor film by a sputtering method.

JP 2003-115718 A

  However, when a thick conductor film, for example, a conductor film having a thickness of about 3 μm, is formed by sputtering, there is a problem that the substrate is deformed and cracks are generated in the conductor film due to the stress (stress) generated during sputtering.

  In order to solve the above-described conventional problems, the present invention provides a high-frequency planar antenna that is stable and has low radio wave loss, and a method for manufacturing the same.

The planar antenna of the present invention is a planar antenna comprising a substrate made of a dielectric, a predetermined pattern formed on the substrate, and a conductor film that covers the surface of the substrate other than the predetermined pattern. The conductor film includes at least a first conductor film and a second conductor film, the first conductor film is formed on the substrate by a sputtering method, and the second conductor film is formed of the first conductor film. It is formed by plating on the conductor film, and the film thickness d ₁ of the first conductor film satisfies the requirement of the following formula (1).
d ₁ ≧ (2 / σ ₁ ωμ ₁ ) ^1/2 (1)
In Equation (1), ω = 2πf, σ ₁ is the conductivity of the first conductor film, f is the frequency of the high-frequency signal to be used, and μ ₁ is the magnetic permeability of the first conductor film. . In the above, f is preferably 30 to 300 GHz.

A method for manufacturing a planar antenna according to the present invention includes a substrate comprising a dielectric substrate, a predetermined pattern formed on the substrate, and a conductor film that covers the surface of the substrate other than the predetermined pattern. In the method for manufacturing an antenna, the conductor film includes at least a first conductor film and a second conductor film, and the film thickness d ₁ of the first conductor film satisfies the requirement of the following formula (1): The method includes a step of forming a first conductor film on the substrate by a sputtering method and a step of forming a second conductor film on the first conductor film by a plating method.
d ₁ ≧ (2 / σ ₁ ωμ ₁ ) ^1/2 (1)
In Equation (1), ω = 2πf, σ ₁ is the conductivity of the first conductor film, f is the frequency of the high-frequency signal to be used, and μ ₁ is the magnetic permeability of the first conductor film. .

  According to the planar antenna of the present invention, a first conductor film having a thickness equal to or greater than the skin depth formed by sputtering on at least the substrate, and a second conductor film formed by plating on the first conductor film. Thus, it is possible to provide a high-frequency planar antenna that is stable and suppresses generation of cracks in the substrate and conductor film and that has low radio wave loss, that is, good radio wave characteristics. In addition, according to the method for manufacturing a planar antenna of the present invention, a high-frequency planar antenna that is stable and suppresses generation of cracks in the substrate and cracks in the conductor film and that has low radio wave loss, that is, good radio wave characteristics is inexpensive. Can be manufactured.

It is a schematic sectional drawing which shows the structure of the planar antenna in one Example of this invention. It is a partial expanded sectional view of the conductor film on a board | substrate which shows schematically the structure of the conductor film in the planar antenna in one Example of this invention. It is a schematic sectional drawing for demonstrating the manufacturing method of the planar antenna in one Example of this invention.

In the planar antenna of the present invention, the film thickness d ₁ of the first conductor film is expressed by the following formula (1): d ₁ ≧ (2 / σ ₁ ωμ ₁ ) ^1/2 (where ω = 2πf in the formula (1)). Yes, σ ₁ is the conductivity of the first conductor film, f is the frequency of the high-frequency signal used, and μ ₁ is the permeability of the first conductor film. In the above formula (1), (2 / σ ₁ ωμ ₁ ) ^1/2 means the skin depth (hereinafter, also simply referred to as skin depth), and a film having a skin depth or more on the substrate. Since the first conductor film having a thickness is formed by the sputtering method, a planar antenna having good radio wave characteristics can be obtained.

  Hereinafter, the planar antenna and the manufacturing method thereof according to the present invention will be described with reference to the drawings.

(Flat antenna)
The planar antenna of the present invention is not particularly limited, but can have a disk shape with a diameter of 60 mm and a thickness of 1.2 mm, for example, and is used as a small radial slot antenna. In addition, for example, any antenna composed of a dielectric having a region where a conductor is not covered on a part of a conductor covering surface such as a patch antenna or a microstrip antenna can be applied. In the planar antenna of the present invention, the shape and size are not particularly limited, and may be determined as appropriate according to the application.

  As shown in FIG. 1, the planar antenna 100 of the present invention covers a substrate 1 made of a dielectric, a predetermined pattern formed on the substrate 1, and a surface of the substrate 1 other than the predetermined pattern. And a conductive film 2 to be provided. The predetermined pattern includes a slot pattern 3 and a power supply slot pattern 4.

  The substrate 1 has a predetermined thickness, and the thickness portion serves as a waveguide and functions as a power supply circuit to each slot. In this specification, on the surface of the substrate 1, the portion where the conductor film 2 is formed is defined as the conductor covering surface 5 of the substrate, except for the portion where the slot pattern 3 and the power supply slot pattern 4 are formed. In FIG. 1, the slot pattern 3 is formed on the upper surface (radiation surface) of the substrate 1 as a pattern made of convex portions, and the power feeding slot pattern 4 is formed on the lower surface (power feeding surface) of the substrate 1 on the substrate 1. It is integrally molded. The height of the pattern composed of the convex portions may be the same as the thickness of the conductor film 2 or may be higher than the thickness of the conductor film 2. In the present specification, the “height of the pattern including the convex portions” is indicated by the height from the flat portion of the substrate 1, that is, the height from the conductor covering surface 5. Moreover, it is preferable that the height of the pattern which consists of the said convex part is 1/10 or less of the wavelength which propagates the inside of the board | substrate 1 from a viewpoint that a resonant circuit is not comprised in the height direction of a convex part.

  In the pattern composed of convex portions constituting the slot pattern 3 and the power feeding slot pattern 4, the convex portions preferably have a columnar shape. If the columnar shape has a substantially constant cross-sectional area, even when the slot corrodes, the identity of the slot shape is maintained, and stable characteristics can be maintained over a long period of time.

  In the slot pattern 3, for example, convex portions are formed in a spiral shape on the upper surface of the substrate 1. On the other hand, in the power supply slot pattern 4, for example, a plus-shaped convex portion is formed at the center position of the lower surface of the substrate 1. Note that the shape of the power supply slot pattern 4 is not limited to a plus shape, and may be a cylindrical shape depending on circumstances. Further, if the power supply slot pattern 4 cannot supply power to the slot center of the planar antenna 100, the radiated power pattern becomes biased. Therefore, the power supply slot pattern 4 faces the center of the spiral spiral slot pattern 3 described above. The position is provided with high accuracy.

  Further, it is preferable that the difference between the center of the slot pattern 3 and the center of the power supply slot pattern 4 (center of potential meaning) is within 1/50 of λ (wavelength). Thus, by suppressing the phase shift of the radiated electromagnetic waves, the radiation pattern formed by synthesizing the radiated electromagnetic waves becomes good.

  The slot pattern 3 on the upper surface (radiation surface) side of the substrate 1 and the power supply slot pattern 4 on the lower surface (power supply surface) side of the substrate 1 may be formed separately, but the slot pattern may be formed using an alignment jig or the like. 3 and the power feeding slot pattern 4 are preferably integrally molded at the same time because there is little deviation in the center position.

  Although it does not specifically limit as a dielectric material which comprises the board | substrate 1, From a viewpoint of improving water resistance and corrosion resistance, for example, resin with low dielectric constant and low water absorption, such as cycloolefin polymer resin, can be used. . Low dielectric constant resins generally do not have polar groups with high hydrophilicity in the molecule, and therefore have a small saturated water absorption amount and are hydrophobic. In addition, since the low dielectric constant resin is not porous, it is more water repellent than inorganic materials such as alumina. Specific resins having a low dielectric constant include fluorine resins such as ethylene-tetrafluoroethylene copolymer, aromatic resins such as polystyrene, polyolefin resins such as polypropylene, polyethylene, polymethylpentene, and norbornene, and hydrocarbons. Resin, dimethanonaphthalene resin and the like. In addition, in order to reduce a thermal expansion coefficient etc., it is also possible to mix fillers and fibers, such as silicon dioxide, with these resins as needed. In view of cost and process, hydrocarbon resins are particularly preferable. When considering use at a high frequency of 50 GHz or more, dimethanonaphthalene resin is excellent.

  Further, as the dielectric constituting the substrate 1, it is preferable to use a resin having a water absorption of 0.01% or less from the viewpoint of further improving water resistance and corrosion resistance. Such resins include polyolefin resins such as polypropylene, polyethylene, polymethylpentene, and norbornene.

Further, as the dielectric constituting the substrate 1, it is preferable to use a resin having a thermal expansion coefficient of 7 × 10 ⁻⁵ or less from the viewpoint of further improving water resistance and corrosion resistance. Such resins include, for example, dimethanonaphthalene resins.

  As shown in FIG. 2, the conductor film 2 includes a first conductor film 21 formed on the substrate 1 and a second conductor film 22 formed on the first conductor film 21. In FIG. 2, only the cross-sectional structure of the conductor film 2 formed on one surface of the substrate 1 is shown, but in actuality, it is formed so as to cover both surfaces of the substrate 1.

  The conductor film 2 is not particularly limited as long as it is made of a conductor material. As the conductive material, for example, copper, silver, nickel or the like can be used, and copper is preferable from the viewpoint of use for high frequency. Moreover, the 1st conductor film 21 and the 2nd conductor film 22 may be comprised with the same conductor material, and may be comprised with a different conductor material.

The first conductor film 21 is formed by a sputtering method. Thereby, a conductor film with high electrical conductivity is obtained. The film thickness d ₁ of the first conductor film 21 is equal to or greater than the skin depth. Thereby, the influence of the skin effect can be eliminated. Further, the film thickness d ₁ of the first conductor film 21 is preferably 2 μm or less from the viewpoint of preventing deformation of the substrate and cracks in the conductor film when the first conductor film is formed by sputtering. .

For example, when the first conductor film 21 is made of copper, the skin depth is as follows. Since copper is a non-magnetic material, the magnetic permeability is almost equal to the magnetic permeability in air, and μ≈4π × 10 ⁻⁷ (H / m). Further, since the electrical conductivity σ of copper is σ = 58.1 × 10 ⁶ (s / m), the skin depth d of the first conductor film is defined as d≈2. 09 (1 / f) ^1/2 (μm). When the frequency of the high frequency signal is 60 GHz, d≈0.27 (μm). That is, when the first conductor film 21 is made of copper, the film thickness may be 0.27 μm or more.

  The second conductor film 22 is formed by a plating method. The film thickness of the second conductor film 22 is larger than the film thickness of the first conductor film 21. The first conductor film 21 is formed by a sputtering method, and the second conductor film 22 having a film thickness larger than the film thickness of the first conductor film 21 is formed on the first conductor film 21 by a plating method. Even if the film thickness exceeds 2 μm, the conductor film 2 can be a stable conductor film that suppresses the deformation of the substrate and the cracks of the conductor film, and a flat antenna with good radio wave characteristics and strength is obtained. can get. In addition, although it does not specifically limit as said plating method, For example, an electrolytic plating method is mentioned.

The first conductor film 21 is formed by a sputtering method and the second conductor film 22 is formed by a plating method, whereby the conductivity σ ₁ of the first conductor film 21 is changed to the conductivity σ of the second conductor film 22. It is higher than ₂ .

The planar antenna 100 may also include a protective layer (not shown) formed on the second conductor film 22 (FIG. 2). Examples of the protective layer include thin films such as a SiO ₂ film and a SiN film. However, it is necessary to use a protective layer that does not affect the radio wave characteristics of the antenna.

  The antenna of the present invention is a small planar antenna suitable for the millimeter wave band (frequency 30 to 300 GHz, wavelength 1 to 10 mm). In particular, the present invention can be applied to various wireless systems with large capacity and low cost. Specifically, the antenna of the present invention is suitable for, for example, a radar for preventing automobile collision, a short-range communication system, a wireless LAN, and wireless indoor wiring at home.

  Next, the manufacturing method of the planar antenna of this invention is demonstrated.

  First, as shown in FIG. 3A, it corresponds to a flat substrate 8 made of a dielectric, a mold 10 having a recess 9 corresponding to the slot pattern 3 (FIG. 1), and a power supply slot pattern 4 (FIG. 1). A mold 12 having a recess 11 to be prepared is prepared.

  Next, as shown in FIG. 3B, for example, a dedicated center alignment is performed so that the center positions of the slot pattern 3 (FIG. 1) and the power supply slot pattern 4 (FIG. 1) match when the substrate 1 (FIG. 1) is completed. Using the jig 13, the flat substrate 8 is sandwiched between the mold 10 and the mold 12 while the positions of the mold 10 and the mold 12 are adjusted. Then, predetermined heat and pressure 15 are simultaneously applied to the flat substrate 8 from the upper surface side of the mold 10 and the lower surface side of the mold 12 by a thermal nanoimprint apparatus (not shown). For example, a pressure of 30 kN is applied at 170 ° C. As a result, the slot pattern 3 (FIG. 1) and the power supply slot pattern 4 (FIG. 1) corresponding to the recess 9 of the mold 10 and the recess 11 of the mold 12 are transferred to the upper surface and the lower surface of the flat substrate 8, respectively. be able to.

  When the mold 10 and the mold 12 are removed after the above transfer, the substrate 1 in which the slot pattern 3 and the power supply slot pattern 4 are integrally formed is obtained as shown in FIG. 3C.

  The slot pattern 3 and the power feeding slot pattern 4 corresponding to the concave portion 9 of the mold 10 and the concave portion 11 of the mold 12 are patterns formed of convex portions. It is preferable that the height of the pattern composed of the above convex portions is about 20 μm in consideration of the polishing described later.

  In this way, a mold having a recess corresponding to a predetermined pattern and a flat substrate made of a dielectric are brought into close contact with each other while applying pressure at a specific temperature, and the predetermined pattern is transferred to the substrate surface. Thus, for example, a slot or a patch can be formed on the substrate surface with high accuracy in units of microns, and finally a small antenna suitable for shortening the wavelength can be manufactured. Furthermore, by using a mold having a recess corresponding to a predetermined pattern, mass production of the substrate 1 having high accuracy and excellent antenna directivity is easy, and finally the antenna can be manufactured at low cost.

  Further, by performing the transfer by the thermal nanoimprint method, it is possible to faithfully reproduce the size and arrangement of the slot pattern 3 and the power feeding slot pattern 4, and the slot pattern 3 having high accuracy and excellent antenna directivity. The board | substrate 1 in which the slot pattern 4 for electric power feeding was integrally formed is obtained. The method is not limited to the thermal nanoimprint method, and an optical nanoimprint method or an injection molding method may be used.

  Next, the conductor film 2 is formed so as to cover the surface of the substrate 1 in which the slot pattern 3 and the power supply slot pattern 4 are integrally formed (hereinafter also simply referred to as a substrate 1 having a predetermined pattern). As a result, the conductor film 2 is uniformly formed on the main body of the substrate 1 in which the slot pattern 3 and the power supply slot pattern 4 are integrally formed. Actually, a conductor film is also formed on the side surfaces of the convex portions which are the slot pattern 3 and the power feeding slot pattern 4, but this is omitted in the drawing.

Specifically, the conductor film 2 is formed as follows. First, the first conductor film 21 (FIG. 2) having a film thickness equal to or greater than the skin depth is formed on the substrate 1 having a predetermined pattern by a sputtering method. For example, when copper having a skin depth of 0.27 μm when the frequency of the high-frequency signal is 60 GHz is used as the conductor material, the film thickness of the first conductor film 21 is 0.27 μm or more, for example, 0.5 μm. It may be. Sputtering can be performed, for example, using a copper target, with a degree of vacuum of 0.15 Pa (in an argon atmosphere) and a sputtering power of 1 kW. In addition, before forming a 1st conductor film, you may perform the surface treatment for improving the adhesive force of the board | substrate 1 and a conductor film with respect to the board | substrate 1 which has a predetermined pattern. Examples of the surface treatment include a reverse sputtering method, a plasma treatment method, and an interface modification method by ultraviolet irradiation. Further, a base film may be formed on the substrate by a sputtering method. Thereby, the roughness (for example, Ra) of the substrate surface is increased and the adhesion is improved. Specifically, the reverse sputtering can be performed using a magnetron sputtering apparatus at a vacuum degree of 0.15 Pa (in an argon atmosphere) and a power of 500 W. The first conductor film is preferably formed simultaneously by sputtering from both sides of the substrate 1 because it is less affected by stress and heat. Next, the second conductor film 22 (FIG. 2) having a film thickness larger than the first conductor film is formed on the first conductor film 21 by plating. For example, when copper is used as the conductor material, the film thickness of the second conductor film 21 may be about 4 μm. Although it does not specifically limit as said plating method, From a viewpoint that the stress of a conductor film can be adjusted and a formation speed is quick, the electrolytic plating method is preferable. The electroplating can be performed, for example, using a copper sulfate bath and a current density of 1.5 A / dm ² while stirring the electrolytic solution. In addition, since the first conductor film 21 is formed on the substrate 1 by the sputtering method, the edge portion 14 of the substrate 1 is compared with the surface of the substrate 1 on which the slot pattern 3 and the power supply slot pattern 4 are formed. The film thickness of the conductor film 2 is thin.

  As described above, the first conductor film 21 having a film thickness equal to or greater than the skin depth is formed by the sputtering method, and the second conductor film having a film thickness larger than the first conductor film 21 is plated on the first conductor film 21. Thus, it is possible to obtain a stable conductor film in which the deformation of the substrate and the occurrence of cracks in the conductor film are suppressed, and a flat antenna having excellent radio wave characteristics and strength can be obtained.

  However, in the state shown in FIG. 3D, the slot pattern 3 and the power feeding slot pattern 4 are patterns composed of convex portions covering the conductor, and do not function as an electrical antenna pattern. Therefore, in order to make the slot pattern 3 and the power feeding slot pattern 4 an electrical antenna pattern, the conductor film 2 covering the slot pattern 3 and the power feeding slot pattern 4 is peeled off. The conductor film 2 covering the slot pattern 3 and the power feeding slot pattern 4 can be peeled off by mechanical means such as grinding or polishing. At this time, the conductor film 2 covering the protrusions forming the slot pattern 3 and the power feeding slot pattern 4 and the tip of the protrusions are simultaneously removed, thereby covering the height of the protrusions and the conductor covering surface 5 of the substrate 1. The height of the conductor film 2 can be made substantially the same. Of course, the present invention does not exclude exfoliating only the conductor film, but it is preferable to remove the tip of the convex portion and the conductor film simultaneously from the viewpoint of ease of manufacture. At this time, it is preferable that the convex portion is columnar so that the slot diameter does not change. In addition, if the flatness of the radiation surface is not sufficient, the polishing is biased and cannot be peeled off well. Therefore, it is preferable that the substrate is not deformed in the manufacturing process of the surface antenna 100 described above.

Through the above steps, as shown in FIG. 3E, the substrate 1, the slot pattern 3 formed in a predetermined region on the substrate 1 and not covered with the conductor film 2 and the feeding slot pattern 4, and the substrate 1 The planar antenna 100 provided with the conductor film 2 covering the conductor covering surface 5 is obtained. After obtaining the planar antenna 100 shown in FIG. 3E, a thin film (not shown) such as a SiO ₂ film or a SiN film may be formed as a protective layer on the second conductor film 22 (FIG. 2). However, it is necessary to use a protective layer that does not affect the radio wave characteristics of the antenna.

  According to the method for manufacturing a planar antenna of the present invention, it is possible to inexpensively manufacture a high-frequency planar antenna that is stable and suppresses generation of cracks in the substrate and cracks in the conductor film and that has low radio wave loss, that is, good radio wave characteristics. . In addition, since the dimensions and positional relationships of all slots can be made uniform with high precision by molding, an antenna with sharp directivity and good characteristics can be obtained. Moreover, since it is excellent in mass productivity, the manufacturing cost can be reduced.

  In the above, the slot antenna is shown as an example. For example, in the patch antenna, only the slot pattern is configured as a conductor film, and other configurations are the same as the slot antenna, and the manufacturing method is not changed. .

  Further, the manufacturing method of the present invention is not limited to an antenna but can be applied to a band pass filter or the like.

  As mentioned above, although one Embodiment of this invention was described, various deformation | transformation and a change are possible for this invention within the range of the summary.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to the following Example.

  Example 1

  First, as shown in FIG. 3A, a flat substrate 8 made of an amorphous polyolefin-based resin, a mold 10 having a recess 9 corresponding to the slot pattern 3 (FIG. 1), and a power feeding slot pattern 4 (FIG. 3). A mold 12 having a recess 11 corresponding to 1) was prepared.

  Next, as shown in FIG. 3B, the center position of the slot pattern 3 (FIG. 1) and the power supply slot pattern 4 (FIG. 1) when the substrate 1 (FIG. 1) is completed using the dedicated center alignment jig 13. The flat plate substrate 8 was sandwiched between the mold 10 and the mold 12 so as to be in close contact with each other while adjusting the positions of the mold 10 and the mold 12 so as to match each other. Then, a pressure 15 of 30 kN was simultaneously applied to the flat substrate 8 from the upper surface side of the mold 10 and the lower surface side of the mold 12 by a thermal nanoimprint apparatus (not shown). As a result, the slot pattern 3 (FIG. 1) and the power feeding slot pattern 4 (FIG. 1) corresponding to the recess 9 of the mold 10 and the recess 11 of the mold 12 were transferred to the upper surface and the lower surface of the flat substrate 8, respectively.

  After completion of the transfer, the mold 10 and the mold 12 were removed to obtain a substrate 1 in which the slot pattern 3 and the power feeding slot pattern 4 were integrally formed as shown in FIG. 3C.

  The slot pattern 3 (FIG. 1) and the power feeding slot pattern 4 corresponding to the concave portion 9 of the mold 10 and the concave portion 11 of the mold 12 are patterns formed of convex portions. The height of the pattern composed of the above convex portions was about 20 μm.

  Next, the conductor film 2 was formed so as to cover the surface of the substrate 1 in which the slot pattern 3 and the power supply slot pattern 4 were integrally formed (hereinafter, also simply referred to as a substrate 1 having a predetermined pattern).

Specifically, the conductor film 2 was formed as follows. First, reverse sputtering was performed on the substrate 1 having the predetermined pattern obtained above using a magnetron sputtering apparatus under a vacuum degree of 0.15 Pa (in an argon atmosphere) and a power of 500 W. Thereby, the roughness (for example, Ra) of the substrate surface was increased, and the adhesion with the first conductor film to be formed later was improved. Subsequently, the 1st conductor film 21 (FIG. 2) which has a film thickness of 0.5 micrometer was simultaneously formed from both surfaces of the board | substrate 1 which has a predetermined pattern using the copper target by sputtering method. Sputtering was performed under the conditions of a vacuum degree of 0.15 Pa (in an argon atmosphere) and a sputtering power of 1 kW. In the above, the film thickness of the first conductor film 21 is larger than the skin depth of 0.27 μm when the frequency of the high-frequency signal is 60 GHz. Next, a second conductor film 22 (FIG. 2) having a film thickness of 4 μm, which is larger than the film thickness of the first conductor film 21, was formed on the first conductor film 21 by electrolytic plating. Specifically, the electrolytic plating was performed using a copper sulfate bath and stirring the electrolytic solution under a current density of 1.5 A / dm ² .

  In the state where the conductor film 2 is formed as described above (FIG. 3D), the slot pattern 3 and the power feeding slot pattern 4 are patterns composed of convex portions covering the conductor, and do not function as an electrical antenna pattern. Therefore, the height of the convex portion, the slot pattern 3 and the power supply slot are removed by polishing, simultaneously removing the conductive film 2 covering the convex portion forming the slot pattern 3 and the power supply slot pattern 4 and the tip portion of the convex portion. The height of the conductor film 2 covering the surface of the substrate 1 other than the pattern 4 was made substantially the same.

  Through the above steps, as shown in FIG. 3E, the substrate 1, the slot pattern 3 formed in a predetermined region on the substrate 1 and not covered with the conductor film 2 and the power supply slot pattern 4, and the slot pattern 3 and the planar antenna 100 provided with the conductor film 2 covering the surface of the substrate 1 other than the power feeding slot pattern 4, that is, the conductor covering surface 5 of the substrate 1.

  As a result of measuring the radio wave characteristics of the planar antenna 100 obtained in Example 1 using a microwave network analyzer manufactured by Agilent, the following results were obtained at a center frequency of 62.5 GHz. The radiation gain was 30 dBi, the antenna directivity (half-value width) was 6 ° horizontal and 6 ° vertical, and the side lobe was 20 dB. In the above, the radiation gain means “a power ratio received in the maximum electric field direction when the same power is applied to the test antenna and the reference antenna”, and is indicated by a value when the isotropic antenna is used as the reference antenna. From the above results, it can be seen that the planar antenna of Example 1 is excellent in radio wave characteristics.

  The planar antenna of the present invention is a small planar antenna suitable for the millimeter wave band (frequency 30 to 300 GHz, wavelength 1 to 10 mm). In particular, the present invention can be applied to various wireless systems with large capacity and low cost. Specifically, the planar antenna of the present invention is suitable for, for example, a radar for automobile collision prevention, a short-range communication system, a wireless LAN, and wireless indoor wiring at home.

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Conductor film 3 Slot pattern consisting of convex part 4 Feeding slot pattern consisting of convex part 5 Conductor coating surface 8 Dielectric flat plate board 9 Recessed part corresponding to slot pattern 10 Slot pattern die 11 Feeding slot pattern Corresponding concave portion 12 Power supply slot pattern mold 13 Center alignment jig 13
14 Edge of substrate 15 Pressure direction during thermal nanoimprint 21 First conductor film 22 Second conductor film 100 Planar antenna

Claims (10)

A planar antenna comprising a substrate made of a dielectric, a predetermined pattern formed on the substrate, and a conductor film covering a surface of the substrate other than the predetermined pattern,
The conductor film includes at least a first conductor film and a second conductor film,
The first conductor film is formed on the substrate by a sputtering method,
The second conductor film is formed on the first conductor film by a plating method,
A planar antenna, wherein the film thickness d ₁ of the first conductor film satisfies the requirement of the following formula (1).
d ₁ ≧ (2 / σ ₁ ωμ ₁ ) ^1/2 (1)
In Equation (1), ω = 2πf, σ ₁ is the conductivity of the first conductor film, f is the frequency of the high-frequency signal to be used, and μ ₁ is the magnetic permeability of the first conductor film. . The planar antenna according to claim 1, wherein the conductivity σ ₁ of the first conductor film is higher than the conductivity σ ₂ of the second conductor film.   The planar antenna according to claim 1 or 2, wherein the predetermined pattern is a pattern including a plurality of convex portions.   The planar antenna according to claim 1, wherein the first conductor film is made of copper.   The planar antenna according to claim 4, wherein the first conductor film has a thickness of 2 μm or less. A method for manufacturing a planar antenna, comprising: a substrate made of a dielectric; a predetermined pattern formed on the substrate; and a conductor film that covers a surface of the substrate other than the predetermined pattern,
The conductor film includes at least a first conductor film and a second conductor film, and the film thickness d ₁ of the first conductor film satisfies the requirement of the following formula (1):
Forming a first conductor film on the substrate by a sputtering method;
Forming a second conductor film on the first conductor film by a plating method.
d ₁ ≧ (2 / σ ₁ ωμ ₁ ) ^1/2 (1)
In Equation (1), ω = 2πf, σ ₁ is the conductivity of the first conductor film, f is the frequency of the high-frequency signal to be used, and μ ₁ is the magnetic permeability of the first conductor film. .   The method for manufacturing a planar antenna according to claim 6, wherein the first conductor film is made of copper.   The method for manufacturing a planar antenna according to claim 6 or 7, wherein the second conductor film is formed by an electrolytic plating method.   The method for manufacturing a planar antenna according to claim 6, wherein the predetermined pattern is a pattern including a plurality of convex portions.   The method for manufacturing a planar antenna according to any one of claims 6 to 9, wherein the predetermined pattern is formed by a thermal nanoimprint method.

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