JP2016034151A - RFID antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an antenna, the antenna has a reduced thickness and cost and is operable when it is mounted on a metallic device and/or placed in an environment surrounded by an electromagnetic field.SOLUTION: The present invention relates to a method for manufacturing an antenna, and the method comprises the steps of: preparing a magnetic sheet made of a composite material including magnetic particles and synthetic resin, the magnetic sheet having a first surface; forming, directly on the first surface of the magnetic sheet, an electrically conductive planar track having at least one turn.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for manufacturing an antenna and an antenna obtained by the method.

  The use of tags with RFID antennas to identify and monitor objects is well known in the art. Such tags include, by way of example, an antenna circuit formed by conductive tracks that are electrically connected to an integrated circuit (IC) chip that includes a memory. This uses the electromagnetic field generated by the RFID reader. If such a tag enters the magnetic field for a sufficient amount of time, the RFID antenna is energized and the electronic circuit can transmit a signal toward the reader or a separate receiving antenna.

  The mode for such non-contact communication between the IC tag and the reader / writer is expected to further diversify in the future. For example, in order to further increase the level of convenience, a mobile communication terminal such as a mobile phone is equipped with a tag function and a reader / writer function.

  For example, by providing a tag function on a mobile phone, the mobile phone can be used to pay a rail fare by holding the phone over a ticket gate of a station.

  In modern RFID systems (eg NFC standard) operating at a frequency of 13.56 MHz, an appropriate operating environment is required. For example, with respect to communication characteristics, a long communication distance is desired, or when a reader / writer and an IC tag face each other, a wide planar communication range is desired.

  However, when such a tag is mounted on an article whose surface is made of a conductive material, or when it is in an environment surrounded by an electromagnetic field, for example in a phone case or on a battery, the resonance of the antenna The frequency is shifted with respect to the nominal resonant frequency. This shift of the resonance frequency affects information exchange between the transponder and the reader / writer device, and as a result, communication is interrupted (detuning of the entire RFID system).

  Furthermore, in order to be practical, such an antenna must also meet the requirements for the space consumed, in particular the antenna should be as thin as possible and as easy to manufacture as possible. Should meet mass production specifications. Thickness issues are especially important when trying to fit the antenna in a mobile phone, especially in a new generation of thin smartphones where space is very limited.

U.S. Patent No. 7,060,418

  It is an object of the present invention to produce an antenna that is reduced in thickness and cost and is operable when mounted on a metal device and / or placed in an environment surrounded by an electromagnetic field. Is to provide a method.

  For this purpose, a method according to claim 1 is provided.

  In fact, due to the claimed features, the antenna conductive track is formed directly on the ferrite sheet which acts as a support substrate in addition to its main function as a shield member, thus reducing the thickness (as thin as 150 μm) It is possible to make an antenna. This eliminates the need to use an additional intermediate support substrate for the antenna and thus also helps to reduce manufacturing tolerance accumulation.

  These and other aspects of the invention are described in detail below by way of example and with reference to the accompanying drawings.

1 is a diagram showing a first embodiment of an antenna according to the present invention. FIG. 6 is a diagram showing a second embodiment of an antenna according to the present invention. FIG. 3 is a cross-sectional view of the antenna along the arrow in FIG. It is the figure which drawn roughly the antenna which has a layered structure.

  The figure is not drawn to scale. In general, identical components in the figures are represented by the same reference numerals.

FIG. 1 shows a first embodiment of a planar RFID antenna with a support substrate 2 on which conductive tracks 4 are formed. In the context of the present invention, the substrate 2 is made of a magnetic flexible sheet comprising magnetic particles (such as magnetic ferrite powder or flakes) dispersed in a resin binder.
An example of such a ferrite sheet is Licalloy (trademark) flexible film sold by Alps Electric Co., Ltd. Such a type of ferrite sheet can also be easily obtained from a ferrite material supplier such as a ferrite material supplier in Japan.

  The conductive track is formed directly on the first major surface of the ferrite sheet such that the conductive track extends in a plane parallel to the first major surface. The conductive track is made of copper as an example. As can be seen in FIG. 1, the antenna track comprises a plurality of turns (here four turns) in the form of a spiral. The outer winding has a connection end that is connected to the connection end of the inner winding through an electrical bridge.

The verb “form” and its conjugations in the context of the present invention encompasses the non-exhaustive methods listed below.
-Conductive foil lamination, and selective chemical etching of the conductive foil after selective masking of the conductive foil using, for example, a photoresist resin- Lamination of already patterned conductive foil by mechanical punching Forming • Conductive ink screen, gravure, inkjet, or offset printing • Placing conductors on the first surface of the magnetic sheet • Chemical vapor deposition of conductive particles

  From a manufacturing point of view, the method is advantageously chosen such that it can be performed by a reel-to-reel process that allows high production rates. Particularly suitable methods for reel-to-reel implementation are the first three methods described above.

  The antenna track can be designed so that its resonant frequency is in the range of 13.56 MHz, for example, so as to meet the NFC standard. In order to adjust the inductance, the gap distance between two adjacent turns and / or the width and / or number of turns of each turn can be varied.

  FIG. 2 shows a second embodiment of the antenna, which differs from the first embodiment in that the two connection ends of the antenna conductive track are not bridged.

  Referring to FIG. 3, which is a cross-sectional view taken along line AA in FIG. 2, it can be seen that the copper ferrite laminate is provided with two blind holes at the level of the two antenna connection ends. These blind holes provide easy access to electrically connect the antenna to the device. The antenna connection end can be mechanically embossed to obtain a reliable electrical connection with the device.

  Next, a preferable process for manufacturing the antenna according to the second embodiment will be described.

The process includes the following steps.
(a) Prepare a ferrite sheet
(b) Applying an adhesive layer on the first surface of the ferrite sheet
(c) Open two through holes in the ferrite sheet
(d) Laminate copper foil on the adhesive layer
(e) Mask the copper layer with mask material to define the antenna pattern
(f) Remove the unmasked area of the copper foil
(g) Remove the mask material to expose the copper track

  Optionally, after step (g), an additional step of plating on the exposed copper track and on the bottom of the blind hole, using a coating such as nickel and gold as an example, can be used, or for corrosion protection. In order to passivate the antenna track, a step can be performed.

  Alternatively, steps (b) and (d) through (g) can be replaced with printing techniques such as those described in US Pat. No. 7,060,418, which is incorporated herein by reference.

  As a result, the applicant has succeeded in obtaining an antenna having a layer structure as schematically depicted in FIG. 4 and having a thickness in the range of 150 to 200 μm.

  A so-called single-sided layered structure with blind holes comprises a ferrite sheet, an adhesive layer on the first surface of the ferrite sheet, and a finally laminated copper layer. Typically, the thickness of the ferrite sheet, adhesive layer, and conductive track is about 100 μm, 20 μm, and 35 μm, respectively.

  Optionally, a second sheet of magnetic material is disposed on the second surface of the composite magnetic sheet described above, i.e., the surface of the first magnetic sheet on which conductive tracks are formed or formed. Are placed on the opposite surface.

  In this embodiment of the invention, two types of ferrite materials are used for the first and second sheets.

  The first sheet is preferably selected so that the value of the imaginary part μ ”of the magnetic permeability is lower than 5 H / m.“ Lower ”is understood as“ lower or equal ”. Due to the low μ ”value of such composite ferrite materials, usually based on polymers, this first magnetic sheet is usually a real part of low values, ie between 40 and 50 H / m. will have μ '.

  With such a low μ ″ value, the finally realized resistance loss of the antenna can be minimized.

  The second sheet of ferrite material is selected to have a high μ ′ value, that is, a value higher than 100 H / m. “Higher” is understood as “higher or equal”. The selection of the value of “μ” is not important.

  Such a second sheet of ferrite material having a high μ ′ value makes it possible to obtain an antenna with an increased Q factor.

  Such a second magnetic sheet can be made from a composite material comprising magnetic particles and a synthetic resin, a sintered type magnetic material, or can be a plain ferrite sheet.

  By using such a combination of the first and second magnetic sheets, the resulting antenna has excellent properties, particularly with respect to reduced resistance loss and Q factor.

  Specifically, the first and second magnetic sheets can be easily obtained from a ferrite material supplier such as a ferrite material supplier in Japan.

In known antenna structures, the layered structure typically comprises:
・ Dielectric substrate (for example, epoxy glass, PET, or polyimide)
-Conductive track formed on the first surface of the dielectric substrate-Ferrite sheet laminated on the second surface on the opposite side of the dielectric substrate

  The main limitations of the known antenna structure are that the total thickness is thick and that the distance between the antenna conductive track and the ferrite sheet is large.

  Although the described embodiment relates to a single-sided antenna, it will be understood by those skilled in the art that a double-sided antenna with conductive holes can also be produced by the method described above.

2 Support substrate
4 Conductive track

Claims (8)

Providing a magnetic sheet made of a composite material including magnetic particles and a synthetic resin, the magnetic sheet having a first surface;
Applying an adhesive layer to the first surface of the magnetic sheet;
A method for manufacturing an antenna comprising:
The method is performed through a reel-to-reel process, and the method further includes laminating a conductive layer on the adhesive layer, and the magnetic layer acting in the conductive layer and as a support substrate. Forming a conductive antenna track having at least one turn directly on a sheet.   The method according to claim 1, wherein a thickness of a laminated structure including the magnetic sheet, the adhesive layer, and the conductive antenna track is in a range of 150 μm to 200 μm.   The method of claim 2, wherein the adhesive layer is 20 μm thick. Forming the conductive antenna track comprises:
Applying the conductive layer on the first surface such that the conductive layer adheres to the first surface;
Selectively protecting the conductive layer by applying a mask pattern on the conductive layer;
Chemically etching the conductive layer to remove the unprotected conductive layer;
And removing the mask pattern to expose the conductive antenna track.   5. The method of claim 4, further comprising plating or passivating the exposed conductive antenna track.   6. The method according to any one of claims 1 to 5, wherein the conductive layer is selected from copper, silver, aluminum, palladium, and graphite.   Disposing a second magnetic sheet on a second surface of the magnetic sheet made of a composite material comprising magnetic particles and a synthetic resin, wherein the second surface is opposite the first surface. The magnetic sheet made of a composite material including magnetic particles and a synthetic resin has a magnetic permeability in which the value of the imaginary part μ ″ is lower than 5 H / m, and the second magnetic sheet has a real part μ ′. 7. The method according to any one of claims 1 to 6, wherein has a permeability higher than 100 H / m.   An antenna obtained by the process according to any one of claims 1 to 7.

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