JP2005295122A - Substrate for antenna, and antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a substrate for an antenna capable of preventing damaged by vibration or impact and scattering of chips, and to provide excellent frequency characteristics for inductance value and Q value, shifting the peak of inductance value toward high frequency side for improved high frequency characteristics, with high selectivity in form. <P>SOLUTION: The substrate for an antenna comprises a core 1 and a coating film 2. The main component of the coating film 2 is resin to cover the core 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an antenna substrate and an antenna, and more particularly to an antenna suitable for a use environment involving intense vibration such as an automobile.

  As this type of antenna, for example, various types of antennas are conventionally known as seen in Patent Documents 1 to 4. Among them, from the viewpoint that a high inductance value can be ensured, for example, an antenna core using an Mn ferrite magnetic material is known.

  Certainly, an antenna using a Mn-based ferrite core has an advantage that a high inductance can be secured.

  However, this ferrite core is inflexible due to its properties as a material, and when used in an in-vehicle antenna or RFID (radio frequency ID), it is damaged by opening and closing of doors and facilities, or external vibration or impact. However, there is a risk of damage to other parts due to the scattering of the fragments.

  Further, since it is not easy to give the ferrite core an arbitrary shape, the ferrite core is not necessarily compatible with application to a vehicle-mounted antenna or RFID (radio frequency ID).

As a means for avoiding this problem, Patent Document 2 discloses a core that uses a ferrite-containing resin and is strong against vibration and hardly cracked. However, the electromagnetic characteristics are inferior compared to the ferrite core.
Japanese Utility Model Publication No. 7-20708 JP-A-6-13243 JP-A-6-59046 No. 6-15437

  An object of the present invention is to provide an antenna substrate that can be prevented from being broken by scattering or vibration due to vibration or impact, and an antenna using the antenna substrate.

  Another object of the present invention is to provide an antenna substrate and an antenna having excellent frequency characteristics with respect to an inductance value and a Q value.

  Still another object of the present invention is to provide an antenna substrate and an antenna which have an improved high frequency characteristic by shifting the peak of the L value to the high frequency side.

  Still another object of the present invention is to provide an antenna substrate and an antenna that are rich in shape selectivity.

  In order to solve the above-described problem, an antenna substrate according to the present invention includes a core and a coating film. The coating film has a resin as a main component and covers the core.

  The board | substrate which concerns on this invention comprises an antenna with an antenna conductor. The antenna conductor is provided on the coating film.

  Here, the coating film has a resin as a main component and covers the core, so that even when the core is made of, for example, a Mn-based ferrite magnetic body, the core is damaged by vibration or impact, and the fragment is Scattering can be prevented by a coating film containing resin as a main component.

  In addition, by covering the core with a coating film containing resin as a main component, an antenna having excellent frequency characteristics with respect to the inductance value (L value) and the Q value can be obtained.

  Further, by covering the core with a coating film containing a resin as a main component, an L value peak can be shifted to the high frequency side, and an antenna with improved high frequency characteristics can be obtained.

  Furthermore, by covering the core with a coating film mainly composed of a resin, even if the core is made of a conductive material, an antenna conductor is formed on the coating film to reduce the thickness. A vehicle-mounted antenna or RFID (radio frequency ID) can be obtained.

  The core can be preferably made of a Mn-based ferrite magnetic material. In this case, a high L value and Q value can be secured by utilizing the high magnetic permeability characteristics of the Mn ferrite magnetic material.

  The core can also be made of a Ni-based ferrite magnetic material. In this case, the excellent high frequency characteristics of the Ni-based ferrite magnetic material can be used effectively. Furthermore, from the viewpoint of high resistance or low price, Mg-based ferrite magnetic materials are also effective.

  The core may be a single plate-like body or may be composed of a plurality of divided pieces. In the latter case, the divided pieces are each covered with a coating film and integrated. The advantage of this structure appears particularly when the core is made of a ferrite magnetic material. This is because by cracking a ferrite magnetic material that is easily cracked in advance, it is possible to avoid cracks during production and use, and to prevent characteristic changes caused by the cracks.

  Moreover, the advantage which can be designed in arbitrary shapes is also acquired by fragmenting. This advantage can be obtained not only in the case of a ferrite magnetic body but also when another magnetic body is selected.

  The coating film is generally a resin, but may be a composite material containing magnetic powder and resin. As the magnetic powder, various magnetic materials can be selectively used. Among them, a Mn-based ferrite magnetic body is preferable from the viewpoint that a high L value and a Q value can be secured. From the viewpoint of improving the high frequency characteristics, a Ni-based ferrite magnetic material is also effective. Furthermore, from the viewpoint of high resistance or low price, Mg-based ferrite magnetic materials are also effective. These ferrite magnetic materials may be used alone or in combination. Alternatively, other magnetic powder may be included as the third component.

  The film thickness of the coating film is selected according to the shape, thickness, and planar area of the core. Actually, a film thickness in the range of 0.1 to 30 mm is sufficient.

  Other features of the present invention and the operational effects thereof will be described in more detail by embodiments with reference to the accompanying drawings.

  FIG. 1 is a perspective view showing a part of one embodiment of an antenna substrate according to the present invention, and FIG. 2 is a cross-sectional view showing a part of the antenna substrate shown in FIG. The illustrated antenna substrate (hereinafter referred to as a substrate) includes a core 1 and a coating film 2. The illustrated core 1 has a flat plate shape. The material of the core 1 is not particularly limited, but can preferably be composed of a Mn-based ferrite magnetic material. In this case, a high L value and Q value can be secured by utilizing the high magnetic permeability characteristics of the Mn ferrite magnetic material.

  The core 1 can also be composed of a Ni-based ferrite magnetic material. In this case, the excellent high frequency characteristics of the Ni-based ferrite magnetic material can be used effectively.

  Furthermore, the core 1 can also be comprised by Mg type ferrite magnetic body. In this case, a merit of high resistance or low price can be obtained.

  The coating film 2 is made of a resin material and covers the core 1. As the resin material constituting the coating film 2, a thermosetting resin such as an epoxy resin is suitable. The coating film 2 may be a composite material containing magnetic powder and resin. Various magnetic materials can be selectively used as the magnetic powder. Among these, a Mn-based ferrite magnetic body is preferable from the viewpoint that a high L value and a Q value can be secured. From the viewpoint of improving the high frequency characteristics, a Ni-based ferrite magnetic material is also effective. These ferrite magnetic materials may be used alone or in combination. Alternatively, other magnetic powder may be included as the third component.

  The film thickness of the coating film 2 is selected according to the shape, thickness, flat area, etc. of the core 1. Actually, a film thickness in the range of 0.1 to 30 mm is sufficient. Preferably, it is the range of 0.5-10 mm, More preferably, it is the range of 0.5-5 mm. However, when the volume of the core 1 increases, it may exceed 30 mm, and when the volume of the core 1 decreases, it may be thinner than 0.1 mm.

  The core 1 may be a single plate-like body, but may be composed of a plurality of divided pieces. An example is shown in FIGS. FIG. 3 is a perspective view showing another embodiment of the antenna substrate according to the present invention, and FIG. 4 is a cross-sectional view showing a part of the antenna substrate shown in FIG. In the figure, the core is composed of a plurality of divided pieces 11 to 15. Each of the divided pieces 11 to 15 is disposed on the same plane, and the whole is covered with the coating film 2 and integrated. The advantage of this structure appears particularly when the core 1 is made of a ferrite magnetic material. This is because by cracking a ferrite magnetic material that is easily cracked in advance, cracks during manufacturing or use can be avoided, and changes in characteristics caused by the cracks can be prevented.

  Moreover, it becomes possible to design a shape arbitrarily by making it into pieces. This advantage can be obtained not only in the case of a ferrite magnetic body but also when another magnetic body is selected.

  FIG. 5 is a perspective view showing a part of an antenna using a substrate according to the present invention, and FIG. 6 is a cross-sectional view showing a part of the antenna shown in FIG. This antenna is used for, for example, a vehicle-mounted antenna or RFID. The substrate 3 according to the present invention constitutes an antenna together with the antenna conductor 4. The shape of the substrate 3 is arbitrary, and the illustration is merely an example.

  The antenna conductor 4 is provided on the coating film 2. The antenna conductor 4 can be realized as a printed wiring. Although the antenna conductor 4 is formed on one surface of the substrate 3 in the illustrated embodiment, the antenna conductor 4 may have a structure in which the width of the substrate 3 is reduced and wound as a winding type. Further, the pattern is not limited to the meandering pattern shown in the figure, but may be a spiral pattern. Further, the antenna may be limited to a size necessary for itself, or may have a shape having a large flat area, and a part or most of the components of the transmission circuit or the reception circuit are mounted together with the antenna conductor 4. It may be.

  Here, since the coating film 2 is mainly composed of resin and covers the core 1, even when the core 1 is made of, for example, a Mn-based ferrite magnetic material, the core 1 is damaged by vibration or impact. However, it is possible to prevent the fragments from being scattered by the coating film 2 containing resin as a main component.

  In addition, by covering the core 1 with the coating film 2 containing resin as a main component, an antenna having excellent frequency characteristics with respect to the inductance value (L value) and the Q value can be obtained. This point will be described in detail later with reference to data.

  Further, by covering the core 1 with the coating film 2 containing a resin as a main component, an antenna having an improved high frequency characteristic can be obtained by shifting the peak of the L value to the high frequency side.

  Further, by covering the core 1 with a coating film 2 containing a resin as a main component, the antenna conductor 4 is formed on the coating film 2 even if the core 1 is made of a conductive material. In addition, a thin vehicle-mounted antenna or RFID (radio frequency ID) can be obtained.

  In particular, by making the core 1 into a flat plate shape, it is possible to configure a vehicle antenna or RFID (radio frequency ID) that is thin and suitable for carrying.

Next, the effect of the present invention will be described with experimental data.
1. Drop test An antenna having a coating film 2 on the entire six surfaces of the core 1, and three samples 1 to 3 having a thickness of the coating film 2 of 1 mm, 1.5 mm, and 2 mm, and a ferrite alone as a core Used were a sample 4 having no coating film, and a sample 5 using a composite material of ferrite powder and resin as a core and not having a coating film. Specific conditions of each sample are as follows.

Sample 1
Core 1
Mn-based ferrite Dimensions: 40 × 6 × 3 (mm)
Coating film Coating thickness: 6mm on all 6 surfaces
Resin: Epoxy resin

Sample 2
Core Mn-based ferrite Dimensions: 40 x 6 x 3 (mm)
Coating film Coating thickness: 1.5 mm for all 6 surfaces
Resin: Epoxy resin

Sample 3
Core Mn-based ferrite Dimensions: 40 x 6 x 3 (mm)
Coating film 2
Covering thickness: 6mm on both sides
Resin: Epoxy resin

Sample 4
Core Mn based ferrite core Dimensions: 40 × 6 × 3 (mm)

Sample 5
Core Composite material of Mn ferrite powder and epoxy resin Dimensions: 40 × 6 × 3 (mm)
Five of each of the above samples 1 to 5 were prepared, and a drop test was performed from heights of 0.5 m, 1 m, and 1.5 m. Table 1 shows the drop test results.

表１を見ると、フェライト単体を用いたサンプル４（従来品）は、０．５ｍの高さからの落下試験でさえ、５個中３個に破損又は割れが発生した。複合材料を用いたサンプル５は５個中一個にも、破損や割れは発生しない。しかし、後に述べるように、Ｌ値やＱ値の劣化が見られる。

As shown in Table 1, sample 4 (conventional product) using ferrite alone was broken or cracked in 3 out of 5 even in a drop test from a height of 0.5 m. The sample 5 using the composite material does not break or crack even in one out of five. However, as will be described later, deterioration of the L value and the Q value is observed.

  In contrast, Samples 1 to 3 that fall within the scope of the embodiment of the present invention do not cause breakage or cracking in the case of a drop test from a height of 0.5 m. In contrast, there is a significant improvement effect.

  In Samples 1 to 3, the probability of breakage or cracking increases as the height of the drop test increases, but in Sample 3 with a coating film thickness of 2 mm, no breakage or cracking occurs. Thus, it can be seen that the probability of breakage and cracking can be reduced by increasing the thickness of the coating film.

  Of course, the probability of breakage and cracking also changes depending on the weight of the core, but the results of the above drop test show that by following it and changing the film thickness of the coating film, breakage and cracking can be avoided. ing.

2. L-value and Q-value measurement test (1) Q-value measurement test Sample 6 (embodiment) of an antenna having a coating film on the entire six surfaces of the core, and sample 7 having a coating film on the five surfaces of the core ( Embodiment) and Sample 8 (Comparative Example) using ferrite alone as a core and having no coating film were prepared. Specific conditions of each sample are as follows.

Sample 6
Core Mn-based ferrite Dimensions: 62 × 10 × 5 (mm)
Coating film Coating thickness: 6mm on all 6 surfaces
Resin: Epoxy resin Antenna conductor Number of turns: 20 (turns)

Sample 7
Core Mn-based ferrite Dimensions: 62 × 10 × 5 (mm)
Coating film Coating thickness The coating thickness of the surface facing the uncoated main surface was 2 mm, and the other surface was 1 mm.
Resin: Epoxy resin Antenna conductor Number of turns: 20 (turns)

Sample 8
Core Mn ferrite core single unit Dimensions; 62 × 10 × 5 (mm)
Antenna conductor Number of turns: 20 (turns)
Q value was measured about the said samples 6-8. The measurement conditions are as follows.
Measuring instrument; LCR meter 4285A
Current value: 1.0mA
Measurement frequency: 75 (kHz) to 30 (MHz)
(In Fig. 7, the range from 1MHz to 30MHz is displayed.)

  FIG. 7 shows the measurement data. In FIG. 7, the horizontal axis represents frequency (MHz) and the vertical axis represents Q value. Curve Q11 is the characteristic of sample 6, curve Q12 is the characteristic of sample 7, and curve Q13 is the characteristic of sample 8.

  Referring to FIG. 7, samples 6 and 7 corresponding to the embodiment according to the present invention have a higher Q value than sample 8 corresponding to the conventional product in a wide frequency range of 6 (MHz) to 15 (MHz). Show.

(2) L value and Q value measurement test A sample of an antenna according to the present invention, in which a sample 9 having an organic coating film on the entire six surfaces of the core and a composite material of ferrite powder and resin were used as the core A sample 10 and a sample 11 using a ferrite simple substance as a core and having no coating film were prepared. Specific conditions of each sample are as follows.

Sample 9
Core Mn-based ferrite Dimensions: 100 × 16 × 4.8 (mm)
Coating film Composite material of Mn-based ferrite powder, PPS resin and coupling material Particle size of Mn-based ferrite powder: 15 μm
Covering thickness: 6mm on both sides
Antenna conductor Number of turns: 30 (turns)

Sample 10
Core Composite material of Mn-based ferrite powder, PPS resin and coupling material Particle size of Mn-based ferrite powder: 15 μm
Dimensions: 100 x 16 x 4.8 (mm)
Antenna conductor Number of turns: 30 (turns)

Sample 11
Core Mn ferrite core single unit Dimensions; 100 × 16 × 4.8 (mm)
Antenna conductor Number of turns: 30 (turns)
About the said samples 9-11, L value and Q value were measured. The measurement conditions are as follows.
Measuring instrument; LCR meter 4285A
Current value: 1.0mA
Measurement frequency: 75 (kHz) to 30 (MHz)
(The range from 1MHz to 30MHz is displayed in Figs. 8 and 9)

  FIG. 8 shows the L value measurement results of the samples 9 to 11 obtained by the measurement, and FIG. 9 also shows the Q value measurement results. In FIG. 8, the curve L11 indicates the characteristics of the sample 9, the curve L12 indicates the characteristics of the sample 10, and the curve L13 indicates the characteristics of the sample 11. In FIG. 9, the curve Q21 indicates the characteristics of the sample 9, the curve Q22 indicates the characteristics of the sample 10, and the curve Q23 indicates the characteristics of the sample 11.

  First, referring to FIG. 8, in the conventional sample 10 using a composite material as a constituent material of the core, the L value is extremely low at all frequencies. In addition, the L value of the conventional sample 11 using a single ferrite also decreases rapidly in the vicinity of 20 (MHz). On the other hand, in the case of the sample 9 which is an embodiment according to the present invention, a high L value is obtained up to a high frequency region in the range of 20 (MHz) to 30 (MHz), and the characteristics on the high frequency side are improved. I understand that.

  Next, referring to FIG. 9, in the sample 10 which is a conventional product, the Q value is low at all frequencies. In addition, the Q value of the conventional sample 11 using a single ferrite starts to decrease when it exceeds 7 (MHz). On the other hand, in the case of the sample 9 which is an embodiment of the present invention, a Q value significantly higher than that of the samples 10 and 11 is obtained in the entire frequency region up to 15 (MHz).

  Although the contents of the present invention have been specifically described above with reference to the preferred embodiments, it is obvious that those skilled in the art can take various modifications based on the basic technical idea and teachings of the present invention. It is.

It is a perspective view which shows a part in one Embodiment of the board | substrate for antennas which concerns on this invention. It is sectional drawing which shows a part of antenna board | substrate shown in FIG. It is a perspective view which shows another embodiment of the board | substrate for antennas which concerns on this invention. FIG. 4 is a cross-sectional view showing a part of the antenna substrate shown in FIG. 3. It is a perspective view showing a part in one embodiment of an antenna using a substrate concerning the present invention. It is sectional drawing which shows a part of antenna shown in FIG. It is a figure which shows Q value measurement data. It is a figure which shows the L value measurement result of the samples 9-11. It is a figure which shows the Q value measurement result of samples 9-11.

Explanation of symbols

1 Core 2 Coating film 3 Antenna conductor

Claims (9)

  An antenna substrate including a core and a coating film, wherein the coating film includes a resin as a main component and covers the core.   2. The antenna substrate according to claim 1, wherein the core is a flat ferrite magnetic body. The antenna substrate according to claim 1 or 2,
The core is a plurality of divided pieces,
Each of the divided pieces is an antenna substrate that is covered and integrated with the covering film.   3. The antenna substrate according to claim 1, wherein each of the divided pieces is disposed on the same plane.   5. The antenna substrate according to claim 1, wherein the core includes at least one of a Mn-based ferrite magnetic body, a Ni-based ferrite magnetic body, and a Mg-based ferrite magnetic body.   6. The antenna substrate according to claim 1, wherein the coating film is made of a composite material including magnetic powder and resin.   The antenna substrate according to claim 6, wherein the magnetic powder includes at least one of a Mn-based ferrite magnetic body, a Ni-based ferrite magnetic body, or a Mg-based ferrite magnetic body.   8. The antenna substrate according to claim 1, wherein the coating film has a thickness in a range of 0.1 to 30 mm. An antenna including a substrate and an antenna conductor,
The substrate is the one described in any one of claims 1 to 8,
The antenna conductor is an antenna provided on the coating film.

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