Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q7/00—Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F17/00—Fixed inductances of the signal type 
  • H01F17/0006—Printed inductances
  • H01F17/0013—Printed inductances with stacked layers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F41/00—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties
  • H01F41/02—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets
  • H01F41/04—Apparatus or processes specially adapted for manufacturing or assembling magnets, inductances or transformers; Apparatus or processes specially adapted for manufacturing materials characterised by their magnetic properties for manufacturing cores, coils, or magnets for manufacturing coils
  • H01F41/041—Printed circuit coils
  • H01F41/045—Trimming
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
  • H01F17/00—Fixed inductances of the signal type 
  • H01F17/0006—Printed inductances
  • H01F2017/004—Printed inductances with the coil helically wound around an axis without a core

Definitions

• the present invention relates to an inductor, such as for example an antenna for a radio identification transponder or such as for example a power transmission antenna.
• Radio-identification is a method of remotely identifying objects or individuals, when stationary or movement, and exchange with them data that is a function of the intended applications.
• An RFID system conventionally comprises:
• a reader or scanner which is a so-called active device, which sends an electromagnetic wave carrying a signal towards the objects to be identified or controlled.
• the reader is able to receive information.
• a tag or transponder also called a "tag” in English, which is fixed or integrated into the object to be identified, and which interacts at a specific frequency with the reception of the signal sent by the reader by sending back to the latter the information requested,
• the reader being a smartphone for example.
• An RFID transponder comprises a chip or microprocessor, possibly equipped with a memory, for example of the EEPROM type, and connected to a so-called coiled antenna or to an antenna formed by a dipole, that is to say one comprising several turns.
• the reader and the tag can interact according to several modes of interaction. One of these modes is the coupling of inductive or magnetic nature.
• NFC Near Field Communication
• a multilayer antenna is particularly known from JP4826195 or from EP 2 779 181.
• Such an antenna comprises a superposition of layers each comprising several turns, the different layers being connected to each other by the intermediate conductive bridges or vias, so as to form a continuous coil composed of several layers of turns.
• the turns are superimposed, that is to say are positioned facing each other in the stacking direction of the layers.
• the resonance frequency of the transponder is in particular a function of the inductance and the capacity of the antenna, and the capacity of the chip.
• the inductance and the capacity of the antenna are in particular a function of the amount of turns of the coil formed by the antenna and the geometry, the dimensions of said turns and the number of conductive layers.
• the various parameters are adjusted by calculation, for example, so as in particular to tune the transponder to the chosen resonant frequency.
• the alignment between the turns during the superposition of the different layers of a multilayer antenna is an element directly influencing the resonant frequency.
• the resonance frequency obtained is offset from the desired resonant frequency, degrading the performance of the transponder or rendering it inoperative during use. It is therefore essential to respect a good alignment of the turns of the different layers of the antenna.
• the document US 2006/0022770 discloses the production of an electronic component comprising a plurality of stacked elements each comprising a conductive layer and a substrate, the elements being assembled together, for example by sintering. During such an assembly, the elements are positioned relative to one another, conductive or vias bridges being made by drilling and adding a conductive metal material in the hole thus formed so as to create an electrical bridge between the conductive layers of the elements. [13] Such a process is complex and expensive to implement. Moreover, the electrical component thus produced has a rigidity and a large thickness, each element consisting of a thick substrate and a conductive layer.
• the conductive layers are made by a chemical etching process, requiring the use of pollutants. Regulations in many countries strictly or even forbid such processes.
• an inductor made on a plastic substrate is not recyclable, such an inductor can not be used in a short-term application, such as, for example, use in a disposable transport ticket.
• the invention applies more generally to any type of inductor having a stack of turns.
• Such an inductor may for example be used in the context of wireless energy transmission by electromagnetic induction.
• a field of application is for example the charging of electronic devices battery or the non-contact power supply of an electric circuit.
• An example of an application may especially be the non-contact supply of light-emitting diodes integrated into the packaging of a product.
• the invention aims to meet the aforementioned technical constraints in a simple, reliable and inexpensive manner.
• an inductor comprising at least a first conductive layer comprising at least a first turn of conductive material and at least a second conductive layer comprising at least a second turn of conductive material, at least one conductive bridge connecting the first and second turns, a layer of insulating material being interposed at least partially between the first and second and second turns, the first and second turns being superimposed at least in part in the stacking direction of said layers, characterized in that, in the superposition zone of said turns, the width of the section of the first turn is larger than the width of the section of the second turn.
• a section of a turn may be defined as the intersection of an area of the turn with an intersection plane perpendicular to the plane of the turn or layer concerned, said intersection plane being parallel to the stacking direction of the layers.
• the width of said section is defined by width along an axis perpendicular to the direction of stacking of the layers and perpendicular to the direction of extension of the turn, in the area of the turn .
• the thickness of said section along the axis of the turn is defined by thickness.
• the stacking direction of the layers can be confused with the winding axis of each turn, also generically called the axis of the turn.
• the capacitance of the inductor, and thus the resonance frequency, is dependent on the superimposing surface.
• the latter can be controlled by the structure of the inductor according to the invention, it is also possible to perfectly control the resonance frequency.
• the spacing of the first turn relative to the second turn along the axis of said turns is controlled by the thickness of the insulating layer between said turns. This spacing also influences the capacitance of the inductor, and therefore the resonance frequency.
• the invention is also directed to the case where the inductor has three or more layers of turns.
• the layers of turns are separated in pairs, at least in part, by insulating layers that can be printed.
• the superposition zone of said turns in the superposition zone of said turns:
• the width of the section of the first turn, belonging to the first conductive layer is greater than the width of the section of the second turn, belonging to the second conductive layer, and the width of the section of the second turn is larger than the width of the section of the third turn, belonging to the third conductive layer.
• the difference in width between the corresponding sections of two turns of two consecutive layers is between 50 and 500 miti, preferably between 100 and 300 pm.
• the turns of the same layer may be spaced from each other by an interval of between 50 and 1000 ⁇ m, preferably between 200 and 600 ⁇ m. [31] Such an interval must be large enough to avoid any risk of short circuit between the turns. This interval must also be small enough to ensure good compactness of the inductor while having a large number of turns. It is therefore a question of finding a good compromise between its different constraints.
• Each conductive layer may be made using a conductive ink.
• the conductive ink may be chosen from the following inks: a carbon-based ink, for example based on graphite or graphene, carbon nanotubes (CNTs),
• an ink based on a conductive polymer material for example polyaniline, poly (3,4-ethylenedioxythiophene), more commonly known as PEDOT, polythiophene or polypyrrole,
• a metal-based ink for example metal microparticles or nanoparticles, for example based on silver, copper, nickel, platinum, tin or gold, in particular a silver-based ink in the form of microparticles or nanoparticles.
• microparticles can be used to designate particles of dimensions between 0.1 and 100 ⁇ m.
• nanoparticles can be used to designate particles of dimensions between 1 and 100 nm.
• the conductive ink may be deposited by a screen printing, flexographic, rotogravure, offset or ink jet printing process.
• Screen printing is a flatbed printing technique in which a canvas is stretched over a frame and then partially obstructed by a photosensitive resin. The ink is forced to pass through the mesh of the fabric, at the level of the unobstructed areas, by the action of a squeegee exerting a pressure on the ink. The ink having passed through the fabric is then deposited on a support.
• Screen printing is an inexpensive, robust and easy to use technique. This technique makes it possible to form layers or deposits ranging from a few hundred nanometers to nearly 100 microns.
• Flexography is a printing technique based on the transfer of an ink onto a substrate using a relief printer form, called a photograph.
• This form is made of rubber or photosensitive polymer. Said form is inked, that is to say covered with a layer of ink, this ink then being transferred to the surface of the substrate by pressing the plate on the substrate.
• Flexography makes it possible to print many substrates at high speeds, the pressure exerted on them being relatively low. Moreover, this technique offers a good print resolution, the fineness of the printed lines being up to about 40 ⁇ m. Moreover, the thickness of the deposited layer may be between 0.8 and 8 ⁇ m.
• Photogravure is a printing technique based on the transfer of ink onto a substrate through an engraved cylinder.
• the cylinder consists of small cells whose depth can be adjusted to form the pattern to be printed.
• Rotogravure can print widths of several meters, at very high speeds, of several hundred meters per minute. Furthermore, this printing technique offers good resolution, with very thin lines of a width of a few tens of micrometers, and allows to deposit layers whose thickness is between 0.5 and 12 pm.
• Offset is a printing technique that uses an almost flat printer shape, such as a flexible aluminum plate coated with a thin film of photosensitive material.
• the pattern is obtained by UV irradiation. Areas not exposed to UV rays are then removed chemically.
• the plate is then attached to a roll, on which the non-printing areas are covered with an aqueous solution called anchorage.
• This solution is easily deposited in the non-printing areas because of the high surface energy in these areas, whereas it can not be deposited on the hydrophobic printing surfaces having a lower surface energy.
• Inking rollers then deposit oily ink, which can not spread over the previously wet areas, this ink is therefore deposited only on the printing areas.
• the ink is then transferred to the substrate, via a compressible elastomeric plate called a blanket, mounted on a roll.
• Offset is a precise printing technique, in terms of the resolution that can reach 15 miti, as well as the positioning between the successive layers. This technique also offers high print rates, of the order of 6000 to 15000 impressions per hour, for example.
• the ink jet is a printing technique consisting of forming and ejecting uniform drops of very small volume, of the order of a few picoliters, using nozzles.
• Inkjet is a printing technique that offers great flexibility and allows you to print any type of substrate with high resolution. Indeed, this technique can print lines whose widths can be between 10 and 50 prn.
• One of the conductive layers may be formed on a substrate.
• the substrate may be made of paper or synthetic paper, such as, for example, the product marketed under the Teslin trademark by PPG Industries, made of polyethylene terephthalate (PET), polyethylene naphthalate (PEN) or polyimide (PI). ).
• PET polyethylene terephthalate
• PEN polyethylene naphthalate
• PI polyimide
• a paper substrate makes it possible to easily recycle the inductor while reducing manufacturing costs.
• Such a substrate also has a small thickness and a high flexibility, while allowing the formation of conductive layers by an additive process printing low pollution, so as to obtain a flat inductor, thin.
• the insulating layer can be made using a UV dielectric ink.
• Such an ink is able to crosslink when it is subjected to the rays
• UV UV.
• Such an ink is for example of the acrylic or polyurethane type.
• the invention also relates to a radio identification transponder characterized in that it comprises an inductor of the aforementioned type forming an antenna, and a chip or printed circuit connected to the antenna.
• the transponder may be tuned to a resonance frequency of 13.56 MHz, plus or minus 5%. Such a frequency corresponds to that used for near-field or NFC communication.
• the chip can be assembled by gluing to the antenna, for example using an anysotropy adhesive electrically conductive in the Z axis.
• the chip may be located in an area of the inductor without an insulating layer, so as to reduce the total thickness of the transponder and prevent the chip from forming a large projecting area. This is particularly relevant in the case where the transponder is laminated between two support sheets, for example two sheets of paper.
• the aforementioned characteristic makes it possible to avoid a crushing of the chip during the rolling operation, said chip then being embedded or partially embedded in the thickness of the conductive and insulating layers of the transponder.
• the conductive bridge between the turns of two superposed layers can be realized in a zone devoid of insulating layer, directly by depositing the second conductive layer on the first conductive layer, in this zone devoid of insulating layer. In this way, the conductive bridge can be obtained without the need for an additional step.
• connection between the different conductive layers does not require via, as is the case in the prior art, in particular in the document US 2006/0022770. We thus get rid of an operation additional drilling and metallization of the hole thus produced.
• the electrical connection between the conductive layers is carried out directly during the additive process of printing the conductive layers on each other, thereby reducing costs and increasing production rates.
• a four-color printing press Cyan, Magenta, Yellow, Black
• the production of an inductor according to the invention can be carried out in a single pass on a single substrate.
• the conductive layers may have a thickness between 0.1 and 100 miti, preferably between 1 and 30 pm.
• the thickness of the conductive layer may be between 1 and 5 ⁇ m.
• the thickness of the conductive layer may be between 4 and 20 ⁇ m.
• Thick conductive layers provide good performance but can penalize the cost of production. It is therefore necessary to find a compromise between these different constraints.
• the insulating layer may have a thickness of between 10 and 60 ⁇ m, preferably between 10 and 40 ⁇ m. A sufficient thickness of insulation is necessary to avoid any short circuit between the turns of the different superimposed layers. However, it is advisable to limit the thickness of the insulating layer so as not to penalize the capacitance of the inductor. Here again, it is important to find a good compromise between these different constraints.
• the thickness of the insulating layer may be between 2 and 20 ⁇ m.
• the thickness of the conductive layer may be between 10 and 50 ⁇ m.
• the inductor may have an area of between 50 and 10,000 mm 2 , preferably between 100 and 400 mm 2 .
• the inductor may have a thickness of less than 20 ⁇ m when the conductive layers are printed flexographically, in the case of an inductor with two superposed conductive layers.
• the inductor may have a thickness of less than 80 ⁇ m when the conductive layers are printed by screen printing, in the case of an inductor with two superposed conductive layers.
• the inductor may have a thickness of less than 50 ⁇ m when the conductive layers are printed flexographically, in the case of an inductor with four superposed conductive layers.
• the inductor may have a thickness of less than 120 ⁇ m when the conductive layers are printed by screen printing, in the case of an inductor with four superposed conductive layers.
• the thickness of such an inductor is relatively small, compared with the electronic components of the prior art made by assembling laminated elements, such as described in particular in the document US 2006/0022770, which which makes it possible to integrate such an inductor easily with a finished product, for example with a packaging.
• a low thickness also offers significant flexibility to the inductor, essential in particular for a coil production.
• the insulating layer may have a permittivity of between 2 and 50.
• the chip may have an internal capacity of between 10 and 100 pF, for example of the order of 17, 23.5, 50 or 97 pF. In the remainder of the description, it will be assumed that the chip has a capacity of 50 pF.
• the quality factor of the transponder is for example between 2 and 20, preferably of the order of 4 to 16.
• the quality factor can also be defined as the ratio of the natural frequency (frequency at which the gain is maximum) to the bandwidth width of the system resonance. In other words, the higher the quality factor, the smaller or the smaller the bandwidth, and the more the resonance is "stitched".
• the quality factor should not be too much high so as not to attenuate by more 3dB the frequencies of the sub-carriers, necessary for the communication with the reader. It must however be important enough to ensure the quality of the detection. As an example, for the IS014443 standard, the optimal quality factor will be between 4 and 9, while it will be between 9 and 16 for the IS015693 standard.
• ⁇ J LC, where L is the inductance of the antenna and where C is the total capacity of the transponder .
• the resistance R is proportional to the number of turns of the antenna and to the total surface of the antenna, and is inversely proportional to the width of the section of the turns, to the spacing between the turns, the thickness of each conductive layer, the conductivity of the conductive ink, and the annealing performance used for the conductive layers.
• the inductance L of the antenna is proportional to the number of turns of the antenna and the surface of the antenna, and is inversely proportional to the width of the section of the turns, and at the spacing between the turns.
• the antenna capacity is proportional to the number of turns of the antenna, to the antenna surface, and to the thickness of each conducting layer and is inversely proportional to the width of the section of the turns, and the spacing between the turns.
• the invention also relates to a method of manufacturing an inductor of the aforementioned type, characterized in that it comprises the steps of:
• first conductive layer comprising at least a first turn of conductive material, forming a layer of insulating material on at least part of the first conductive layer,
• At least a second conducting layer comprising at least a second turn of conductive material, on the layer of insulating material and / or on the first layer, the first and second turns being superimposed at least partly in the stacking direction of said layers the turns being dimensioned and positioned such that in the superposition area of said turns the width of the section of the first turn is larger than the width of the section of the second turn, and so that the turns are connected by at least one conductive bridge.
• the steps of forming the conductive layers can be performed by printing with a conductive ink.
• the method may comprise at least one annealing step of at least one of the conductive layers.
• An annealing step may be performed after each step of printing a conductive layer.
• the temperature and the type of annealing performed can be especially adapted to the support.
• metal inks require heat treatment to evaporate the organic compounds present in their formulation.
• This treatment notably makes it possible to improve the electrical conduction properties of the various conductive layers.
• This step called sintering or coalescing annealing, may be performed by raising the temperature of the ink in an oven or in a hot air tunnel.
• Flexible substrates however, have a low temperature tolerance, which makes it necessary to limit the annealing temperatures.
• the table below gives indicative values for maximum annealing temperatures, for different types of substrates.
• a first technique consists of performing a so-called electrical annealing, when an electric current flows through the turns of the conductive layers so as to selectively cause their heating.
• the duration can be of the order of a few seconds.
• Such annealing is also called fast electrical annealing (RES).
• a second technique is plasma annealing, in which a plasma is used, that is to say an ionized gas generated by the application of a high energy (activation), and which has the effect of exciting the ions present in the gas. It is then a question of using a plasma whose temperature is lower than the maximum temperature of the substrate used.
• a third technique is to perform a microwave annealing, in which the conductive layers are subjected to microwaves so as to cause their selective heating.
• a fourth technique is photonic annealing, which uses electromagnetic radiation from ultraviolet to infrared.
• the characteristic optical absorption of the metal particles allows a selective heating of the majority of the metallic inks, by being placed in a wavelength range chosen so as not to affect (or in a limited way) the substrate.
• Photonic annealing may be laser annealing, infrared annealing, or pulsed xenon light (IPL) annealing.
• Laser annealing of metallic inks consists of irradiating the conductive layers with a motorized laser beam. The wavelength is chosen so as to correspond to the absorption maximum of the ink used.
• Infrared annealing is based on the use of lamps emitting light radiation close to that of a blackbody, with an emission peak of between 0.78 and 3 ⁇ m for the near infrared (NIR) and between 3 e 50 pm for the medium infrared (MIR).
• Pulsed light annealing is a photonic annealing technique in which xenon lamps are pulsed.
• the emitted light radiation extends from the ultraviolet to the near infrared (200 nm to 1000 nm).
• the characteristic duration of a tap is of the order of a few microseconds to a few milliseconds.
• the chip may be deposited at the end of the formation of the antenna, by a process called "pick and place", which consists in taking a unitary chip, comprising for example at least one outgrowth (or “bump” in English), and to come align and deposit on the antenna.
• the assembly of the chip on the antenna can be performed using a crosslinkable adhesive.
• a pressure of a few hundred grams for example may be applied to the chip, so that the protrusion is applied and in contact with the corresponding conductive track.
• a temperature of, for example, between 150 ° C. and 200 ° C. can be applied so as to crosslink the adhesive.
• Such a method makes it possible to obtain a high production rate. It will be noted that such a method can easily be implemented because of the small thickness of the inductor forming the antenna. Indeed, in the case of a thick antenna, the positioning of the chip on the antenna is more complex to achieve.
• FIG. 1 is an exploded perspective view, illustrating an antenna according to a first embodiment of the invention, intended to equip a radio identification transponder, the antenna having two conductive layers;
• FIG. 2 is a view from above of part of the conductive layers of the antenna of FIG. 1,
• FIG. 3 is a sectional view of a portion of a transponder comprising an antenna of FIG. 1,
• FIG. 4 is a diagram representing the characteristic curve of a transponder equipped with the antenna of FIG. 1, representing the evolution of the impedance as a function of frequency;
• FIG. 5 is an exploded perspective view, illustrating an antenna according to a second embodiment of the invention, intended to equip a radio identification transponder, the antenna having four conductive layers;
• FIG. 6 is a sectional view of a portion of a transponder comprising an antenna of FIG. 5.
• FIGS. 1 and 2 An antenna 1 intended to equip a radio identification transponder 2 according to a first embodiment of the invention is illustrated in FIGS. 1 and 2, the transponder 2 being illustrated in FIG. 3.
• the antenna 1 comprises a substrate 3 ( Figure 3) on which is deposited a first conductive layer 4a printed with a conductive ink.
• the first layer 4a is generally flat, said plane being defined by two orthogonal X and Y axes.
• the first conductive layer 4a comprises turns 5 of generally rectangular shape, here four turns 5. Each turn 5 thus comprises straight portions 5a extending along the X axis and straight portions 5b extending along the Y axis.
• Each turn 5 can also include rectilinear areas 5c oblique to the X and Y axes.
• a layer 6a of dielectric or insulating material is deposited by printing over most of the first conductive layer 4a. Some areas of the first conductive layer 4a are not covered with dielectric material 6a.
• a second conductive layer 4b is deposited by printing with a conductive ink.
• the second conductive layer 4b comprises turns 5 of generally rectangular shape, here five turns 5. As before, each turn 5 thus comprises rectilinear portions 5a extending along the X axis and straight portions 5b extending according to the Y axis. Each turn 5 may also comprise oblique straight zones 5c with respect to the X and Y axes.
• the X, Y and Z axes are orthogonal.
• the turns 5 of the first conductive layer 4a are located opposite, along the Z axis, turns 5 of the second conductive layer 4b.
• At least one turn 5 of the second conductive layer 4b is located in a zone devoid of insulating material so that, in this zone, the turn 5 of the second conducting layer 4b is in contact with the corresponding turn 5 of the first conductive layer 4a so as to form a conductive bridge 7.
• the two layers of turns 5 thus form a continuous coil having a total number of turns corresponding to the sum of the turns 5 of the first conductive layer 4a and the turns 5 of the second conductive layer 4b.
• the conductive layers 4a, 4b are preferably only assembled in series, and not in parallel.
• the coil is open in that it comprises two free ends 8 which are electrically connected to a chip or integrated circuit 9 of the transponder 2.
• the chip 9 may be located in a zone devoid of a layer of material dielectric 6a and devoid of turns 5 of the second conductive layer 4b, so as to be housed or embedded, at least in part, in a cavity of the insulating layer 6a and the second conductive layer 4b.
• the chip 9 is fixed by bonding and electrically connected to the corresponding ends 8 of the coil, by means of a conductive adhesive 10 for example.
• the turns 5 of the first conductive layer 4a have a width of section 11 (also called line width) of the order of 500 miti, the interval 11 between the turns 5 (also called spacing) being of the order of 300 ⁇ m.
• the turns 5 of the first conductive layer 4a are thus wider than the turns 5 of the second conductive layer 4b, the difference in width here being of the order of 200 ⁇ m. This ensures that the turns 5 of the second conductive layer 4b are aligned with the turns 5 of the first conductive layer 4a, with a positioning tolerance with respect to a desired nominal position of +/- 100 ⁇ m. Such a tolerance can be obtained with the majority of the usual printing processes used in printing, such as, for example, screen printing, flexography, gravure printing, offset printing or inkjet printing.
• the turns 5 of the first conductive layer 4a and the second conductive layer 4b have a thickness e of between 1 and 40, preferably between 2 and 20.
• the layer of dielectric material 6a has a thickness e 'of between 5 and 50 ⁇ m, preferably between 10 and 30 ⁇ m.
• the transponder has a width I of the order of 10 mm and a length L of the order of 20 mm, ie a surface of the order of 200 mm 2 .
• FIG. 4 is a diagram showing the characteristic curve of the transponder of FIGS. 1 and 2, showing the evolution of the impedance Z as a function of the frequency f. It can be seen that the transponder is perfectly tuned since the resonance frequency f0 is of the order of 13.56 MHz, even in the event of a slight offset of the tracks 5 of the second conductive layer 4b with respect to the tracks 5 of the first conducting layer. 4a. In this case, the offset can be of the order of +/- 100 pm both along the X axis and along the Y axis, without affecting the resonance frequency f0.
• the resonance frequency f0 obtained after transfer of a chip of 50 pF is of the order of 26 MHz, that is to say, much higher than the wanted frequency of 13.56 MHz.
• the transponder should have a width I of the order of 15 mm and a length L of the order of 30 mm is a surface of the order of 450 mm 2 .
• FIG. 5 An antenna 1 for equipping a radio identification transponder according to a second embodiment of the invention is illustrated in FIG. 5, the transponder 2 being illustrated in FIG. 6.
• the antenna 1 comprises a substrate 3 on which is deposited a first conductive layer 4a printed with a conductive ink.
• the first Conductive layer 4a is generally planar, said plane being defined by two orthogonal X and Y axes.
• the first conductive layer 4a comprises turns 5 of generally rectangular shape, here four turns 5. Each turn 5 thus comprises straight portions 5a extending along the X axis and straight portions 5b extending along the Y axis. Each turn may also comprise oblique straight zones 5c with respect to the X and Y axes.
• a first layer of dielectric or insulating material 6a is deposited by printing over most of the first conductive layer 4a. Some areas of the first conductive layer 4a are not covered with dielectric material 6a.
• a second conductive layer 4b is deposited by printing with a conductive ink.
• the second conductive layer 4b comprises coils 5 of rectangular general shape, here four turns. As before, each turn 5 thus comprises rectilinear portions 5a extending along the X axis and rectilinear portions 5b extending along the Y axis. Each turn 5 may also comprise rectilinear zones 5c oblique with respect to the X axes. and Y.
• At least one turn 5 of the second conductive layer 4b is located in a zone devoid of insulating material 6a so that, in this zone, the turn 5 of the second conductive layer 4b is in contact with the corresponding turn 5 of the first conductive layer 4a so as to form a conductive bridge 7.
• a second layer of dielectric or insulating material 6b is deposited by printing over most of the second conductive layer 4b. Some areas of the second conductive layer 4b are not covered with dielectric material 6b.
• a third conductive layer 4c is deposited by printing with a conductive ink.
• the third conductive layer 4c has coils 5 of rectangular general shape, here four turns. As before, each turn 5 thus comprises rectilinear portions 5a extending along the axis X and rectilinear portions 5b extending along the Y axis. Each turn 5 may also comprise rectilinear zones 5c oblique with respect to the X and Y axes.
• At least one turn 5 of the third conductive layer 4c is located in a zone devoid of insulating material 6b so that, in this area, the turn 5 of the third conductive layer 4c is in contact with the corresponding turn 5 of the second conductive layer 4b so as to form a conductive bridge 7.
• a third layer of dielectric or insulating material 6c is deposited by printing over most of the third conductive layer 4c. Some areas of the third conductive layer 4c are not covered with dielectric material 6c.
• a fourth conductive layer 4d is deposited by printing with a conductive ink.
• the fourth conductive layer 4d comprises turns 5 of generally rectangular shape, here four turns 5. As before, each turn 5 thus comprises straight portions 5a extending along the X axis and straight portions 5b extending according to the Y axis. Each turn 5 may also comprise rectilinear zones 5c oblique with respect to the X and Y axes.
• At least one turn 5 of the fourth conductive layer 4d is located in a zone devoid of insulating material 6c so that, in this area, the turn 5 of the fourth conductive layer 4d is in contact with the corresponding turn 5 of the third conductive layer 4d so as to form a conductive bridge 7.
• a conductive bridge also connects the first conductive layer 4a and the fourth conductive layer 4d.
• the turns 5 of the various conductive layers 4a, 4b, 4c, 4d are superimposed.
• Z defines the stacking axis of the layers 4a, 4b, 4c, 4d, 6a, 6b, 6c.
• the X, Y and Z axes are orthogonal. In other words, the turns 5 of the different conductive layers 4a, 4b, 4c, 4d are located facing each other along the Z axis, at least partially.
• the stack of conductive layers is located only on one side of the substrate, which avoids making a via between the two faces, allows for a stack of as many layers as desired or allows have thinner insulating layers.
• the four layers 4a, 4b, 4c, 4d of turns 5 thus form a continuous coil having a total number of turns corresponding to the sum of the turns 5 of the first conductive layer 4a, the turns 5 of the second conductive layer 4b, turns 5 of the third conductive layer 4c and turns 5 of the fourth conductive layer 4d.
• the coil is open in that it comprises two free ends 8 which are electrically connected to a chip or integrated circuit 9 of the transponder 2.
• the chip 9 is fixed by bonding and electrically connected to the corresponding ends 8 of the coil, by the intermediate of a conductive adhesive 10 for example.
• the turns 5 of the first conductive layer 4a have a section width 11 of the order of 900 miti, the gap 11 between the turns 5 being of the order of 300 pm.
• the turns 5 of the second conductive layer 4b have a section width I2 of the order of 700 ⁇ m, the interval i2 between the turns 5 being of the order of 500 ⁇ m.
• the turns of the third conductive layer 4c have a section width I3 of the order of 500 ⁇ m, the interval i3 between the turns 5 being of the order of 700 ⁇ m.
• the turns 5 of the first conductive layer 4a are thus wider than the turns 5 of the second conductive layer 4b.
• the turns 5 of the second conductive layer 4b are wider than the turns 5 of the third conductive layer 4c.
• the turns 5 of the third conductive layer 4c are wider than the turns 5 of the fourth layer conductive 4d.
• the difference in section width of the turns 5 between two adjacent conductive layers being of the order of 200 miti. As before, this ensures that the turns 5 of the different conductive layers 4a, 4b, 4c, 4d are aligned with each other, despite positioning tolerances of +/- 100 pm between the different conductive layers 4a, 4b, 4c, 4d.
• the turns 5 of the first conductive layer 4a, the second conductive layer 4b, the third conductive layer 4c and the fourth conductive layer 4d have a thickness e of between 1 and 40, preferably between 2 and 20.
• the layers of dielectric material 6a, 6b, 6c have a thickness e 'of between 5 and 50 ⁇ m, preferably between 10 and 30 ⁇ m.
• the transponder has a width I of the order of 8 mm and a length L of the order of 16 mm, ie a surface of the order of 128 mm 2 .
• the shape of the turns of each conductive layer may be different from that presented above.
• the turns may have a rounded shape or any polygonal shape.

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• 2017
  • 2017-11-14 FR FR1760670A patent/FR3073662B1/fr active Active
• 2018
  • 2018-11-13 WO PCT/EP2018/081116 patent/WO2019096803A1/fr unknown
  • 2018-11-13 CA CA3081749A patent/CA3081749A1/en not_active Abandoned
  • 2018-11-13 KR KR1020207016228A patent/KR20200089689A/ko unknown
  • 2018-11-13 CN CN201880073428.5A patent/CN111712889A/zh active Pending
  • 2018-11-13 US US16/764,326 patent/US20200287286A1/en not_active Abandoned
  • 2018-11-13 EP EP18799549.3A patent/EP3711073A1/de active Pending

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