FORM-2
THE PATENTS ACT. 1970 (39 of 1970)
COMPLETE SPECIFICATION (Section 10, rule 13)
"A Method for manufacturing RFID Label Antenna"
M-Tech Innovations Ltd
with our principle place of business at Mahavir Chambers, 12 Premanand Society, Balajinagar, Pune-Satara Road, Pune 411043, Maharashtra, India.
an Indian Company registered under the provisions of the Companies Act, 1956.
The following specification particularly describes the nature of the invention and the
manner in which it is to be performed: -
Dated this 1st September, 2005

The present invention relates to a method of manufacturing RFID label antennas using Printing Technology.
More particularly the present invention seeks to provide RFID label antennas by printing process which would have flexibility in the label design, reduce material wastage & make the RFID label more cost effective.
Still particularly, this invention relates to a method of manufacturing RFID label antennas with no open circuits in the antenna and with the contact resistance of the conductive traces printed as the RFID tag antenna maintained in significant range to give better tag performance.
This method of manufacturing RFID label antennas has changed a great deal since the early days of manufacturing RFID labels. Radio frequency identification, or RFID, is a generic term for technologies that use radio waves to automatically identify people or objects. Radio Frequency IDentification (RFID) is a method of storing and remotely retrieving data using devices called RFID tags or transponders. RFID tags consist of two essential components - a chip and an antenna. An RFID tag is a small object that can be attached to or incorporated into a product, animal, or person. RFID tags contain antennas to enable them to receive and respond to radio-frequency queries from an RFID transceiver. Passive tags require no internal power source, whereas active tags require a power source.
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The technology used in RFID has been around since the early 1960's according to one source. Conventionally, RFID tags can be either active or passive. Passive RFID tags have no internal power supply. The minute electrical current induced in the antenna by the incoming radio frequency signal provides just enough power for the tag to transmit a response. Due to limited power and cost, the response of a passive RFID tag is brief— typically just an ID number. Lack of an onboard power supply means that the device can be quite small. Passive tags have practical read distances ranging from about 10 mm up to about 6 metres.
Active RFID tags, on the other hand, have an internal power source, and may have longer range and larger memories than passive tags, as well as the ability to store additional information sent by the transceiver. Many active tags have practical ranges of tens of metres, and a battery life of up to 10 years. Because passive tags are cheaper to manufacture and have no battery, the majority of RFID tags in existence are of the passive variety.
The conventional method of coil winding process of manufacturing the RFID label antennas (which is a part of the tag as explained above) is done by laying a suitable coil in the specified format to make a RFID label antenna. The gap between two tracks of the antenna need to be uniform throughout and the same is difficult to maintain consistently.
Many researchers and technicians have experimented with alternate RFID label antenna manufacturing method. One such alternate method is the etching process the
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copper material is etched from the copper sheet and only the copper material required for laying the label antenna is kept on the substrate. In this process there is a heavy loss of the material since the unwanted material needs to be etched out which is of no use after etching.
Thus in all the alternative RFID label antenna manufacturing techniques, there are problems of maintaining consistency in coil laying or maintaining uniform gap between two tracks of the antenna or instances of heavy loss of the material since the unwanted material while etching.
Up to now, RFID technology has been too expensive and too limited to be practical for many commercial applications. But if tags can be made cheaply enough, they can solve many of the problems associated with bar codes. Radio waves travel through most non-metallic materials, so they can be embedded in packaging or encased in protective plastic for weather-proofing and greater durability. And tags have microchips that can store a unique serial number for every product manufactured around the world.
Although the problems are rapidly becoming more acute, they have been acknowledged by various industries, researchers, technologists, RFID label antennas manufacturers and scientific society in general.
The RFID technology, therefore, needs to be available without been too expensive and too limited to be practical for many commercial applications. The object of this
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invention is to manufacture RFID label antennas by printing method which could make such RFID tags available cheap enough so as to solve many of the problems associated with bar codes.
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A U.S. Patent No. 6,929,412 claims, "An RFID label with embedded tag is passed through an RFID antenna in a printer system, where the RFID antenna allows a roll of such labels to pass in close proximity to the antenna and still allow each individual RFID tag to be read and/or programmed. The RFID antenna is formed with two parallel microstrip transmission lines coupled to an RF phase splitter there between."
A printer system, comprising:
a roll of labels, wherein each label comprises a radio frequency identification (RFID) tag;
an RFID reader system comprising: an RFID reader; and an RFID antenna coupled to the RFID reader,
wherein the RFID antenna comprises: two non-overlapping parallel transmission lines; and a phase splitter coupled between the two transmission lines; and a print head, wherein the RFID antenna is between the roll of labels and the print head.
A U.S. Patent No. 6,899,476 claims, "An RFID label with embedded tag is passed through an RFID antenna in a printer system, where the RFID antenna allows a roll of such labels to pass in close proximity to the antenna and still allow each individual RFID tag to be read and/or programmed. The RFID antenna module is formed with a transmission line coupled to an RF phase splitter, where in one embodiment, the transmission line is formed from two parallel conductive strips."
1. A printer system, comprising:
a roll of labels, wherein each label comprises a radio frequency identification (RFID) tag;
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an RFID reader system comprising: an RFID reader; and an RFID antenna module coupled to the RFID reader,
wherein the RFID antenna module comprises: two electrical conductors, each having a first end and a second end; a resistive element coupled to the second ends of the two conductors; and a phase splitter coupled between the first ends of the two conductors and the RFID reader; and a print head, wherein the RFID antenna is between the roll of labels and the print head.
A U.S. Patent No. 6,593,853 claims, "A radio frequency identification device (RFID) label printing system which includes a printer for printing on a label having RFID circuitry. The printer includes a label exit for expelling a printed label, and an external programming module disposed adjacent the label exit for encoding the label expelled from said label exit. The external programming module can include a label marking mechanism which selectively marks a label to indicate a defective label to a user. A host computer communicatively connected to the printer and the external programming module coordinates the operation of the printer and the external programming module
Wherein a radio frequency identification device (RFID) label printing system comprising:
a printer including a label exit for expelling a printed label having RFID circuitry; an external programming module disposed adjacent said label exit for encoding the label expelled from said label exit, said programming module including an antenna disposed
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adjacent an exit slot of said printer, and having a shield mounted adjacent said antenna for focusing a magnetic field generated by said antenna toward a label being encoded,
wherein said shield is formed from material selected from a group consisting of conductive and magnetic materials; and a host computer communicatively connected to said printer and said external programming module for coordinating the operation of said printer and said external programming module.
These systems and methods of manufacturing RFID Label antennas are complex and are lacking in the development of high quality RFID Label antenna. Most of the above apparatus, systems and methods of manufacturing RFID Label antennas have concentrated only in the area of printer technology but not on screen printing thereby effectively hiking the price of such RFID label antennas.
This process of manufacturing RFID label antennas using Printed Technology is done by Silk screen printing method. Printing technology is used for manufacturing the RFID label antenna ahead of other techniques like Etching or coil winding. The manufacturing process is carried out at & sponsored by M-Tech Innovations Ltd.
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BACKGROUND
Radio Frequency Identification(RFID) labels are used for the applications like Library management, Access control systems, Inventory Control, Jewelry Management systems etc., RFID label consists of an antenna and a chip where the antenna design varies as per the size and application requirements. RFID Labels fall into two broad categories: passive and active. Passive labels are the most simple and consist of the components mentioned above. They obtain power from the radio frequency field of the reader, and therefore don't require an integrated power source. This makes them the most inexpensive tag. Active tags use an on-board power source to achieve either greater range or the ability to record data from a sensor. These tags are usually more complex and therefore cost more.
The antenna of RFID label can be manufactured using the following techniques:-
a) Etching
b) Coil winding
c) Printing
RFID labels comprise two essential components: a silicon chip and an antenna. The chip receives and transmits data, such as a product identification number, via the antenna. The data on the chips can be accessed by a radio frequency signal created by a "reader", an electronic module connected to its own antenna and a computer network. The reader sends a specific signal to RFID tags in the immediate area. These tags then
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respond with an answer, again, such as their unique identification number, which the reader processes and conveys to a computer network.
The major drawbacks while manufacturing the RFID label antenna by Coil winding & Etching process are:-
a) Coil winding process:-
In the coil winding process is done by laying a suitable coil in the specified format to make a RFID label antenna. The limitation of coil winding process is that it is not feasible to use for the UHF RFID labels where the area of antenna is much higher and the consistency in coil laying cannot be maintained. The gap between two tracks of the antenna need to be uniform throughout and the same is difficult to maintain consistently.
b) Etching process:-
In the etching process the copper material is etched from the copper sheet and only the copper material required for laying the label antenna is kept on the substrate. In this process there is a heavy loss of the material since the unwanted material needs to be etched out which is of no use after etching.
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DESCRIPTION OF PRESENT INVENTION
In the present invention, the RFID label antenna is manufactured by printing process using modern screens of aluminum frames with a polyester fabric (screen cloth) stretched across them.
Screen printing is basically a printing process that involves covering the surface to be printed with a material like synthetic fiber or polyester or nylon into which opening have been cut. Because silk was the earliest material stretched across a frame to create a screen, the process became known as Silk Screen Printing. This term is still used today despite the fact that most screens are made of synthetic fibers which are more durable and not as subject to change.
Screen printing is the most versatile color medium. Any conceivable color can be screen printed. Screen printing inks are available to create finishes which range from matted to high gloss; and only with screen printing can ink be laid down so transparently it is almost invisible, or so thick that it appears to be a block print. Screen printing is unparalleled in color and texture versatility. This means that it can be used to print on many different types of surfaces and not confined to paper. Screen printing inks have been designed to be applied to almost any surface: glass, fabric, wood, metal, plastic and many more.
The entire manufacturing by printing process is divided into 4 parts:
I. Artwork preparation;
II. Screen making;
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III. Printing;
IV. Testing and
V. Chip bonding.
I. Artwork preparation:
The graphics to be printed on the base substrate is prepared on the computer to the desired dimensional specification. In this case the RFID label antenna is designed so as to go ahead for the printing purpose.
II. Screen making:
a) Screen
The screens used in this type of printing are commonly made of aluminum or wood frame in the shape of a square or rectangle. It is covered on one side with a tightly stretched and tightly woven mesh fabric. This mesh consists of many different thread counts that range anywhere from 100 to 400 threads per inch. For printing of RFID label antenna a screen of 90T to 120T is recommended. (90T means 90 Threads in one centimeter) The screen must then be coated with a light sensitive emulsion that will accept the artwork image. The screen cloth (polyester fabric) is stretched with automated stretching equipment to achieve accurate tensions, fabric orientation and levels. The coarse density of the screen is important in evaluating the life and/or the number of impressions suited to the printing project. The Screen cloth Fabric (Screen cloth) is stretched over the screen frame

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b) Expose
In order to expose a screen, the artwork must be printed onto a clear or translucent film. The artwork is then put onto an exposure system. This is a large machine with a glass top and a light source at the bottom. The light is activated and shines upward toward the glass. The artwork is placed on the glass and the screen is placed on top of the artwork. The light is then turned on for a controlled amount of time and the screen is exposed.
c) Washout
After the screen is exposed, it is then washed out with high-pressure water. The areas of the artwork that were not exposed to the light wash out with water. It is these areas that the ink will pass through and onto the garment. After, the screen has dried; it is then taped around the edges to prevent ink from leaking onto the printing substrate.
d) Squeegee
Squeegee is the tool which applies the ink. The type of squeegee for printing such RFID label antenna is a Soft squeegee for uniform deposition of the ink on the base substrate and to prevent the screen from damaging since the conductive ink used contains almost 61% of pure Silver. The squeegee is the tool which applies the ink. It pulls the ink across the screen and forces it through the open stencil areas on to the paper or other material being printed. The ink on the screen is checked to ascertain the quantity which should be optimum. The ink is pulled back across the screen with
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a firm, steady stroke using the squeegee. This movement of the squeegee enables the ink to pass through the stencil and prints the image on the material under the stencil.
III. Printing:
a) Setting
After the screen is prepared for ink, it is then loaded into the printer. It is aligned and adjusted for height. It is then ready to print. The ink is poured on the screen and squeegee is used to apply the ink on the base substrate. Since this method of manufacturing RFID label antenna is by printing method, it inevitably calls for applying ink to the screen. The ink is spread evenly along one side of the stencil (on the top, bottom, right or left side of the image).
b) Loading the screen
After the screen is clamped, the ink is placed in the screen. Along with the ink, a squeegee is placed in the screen to press the ink onto the base material to be printed.
c) Printing
With the material to be printed in place, the screen is then lowered onto the base material. The squeegee is then drug across the screen to distribute the ink. The squeegee is then pulled across the screen while applying pressure to push the ink through the screen and onto the base substrate. The pressure and angle the position the squeegee can be varied to adjust for better printing. The Printing conditions for
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manufacturing the RFID label antenna is of a room temperature around 25 deg. Celsius to 30 deg. Celsius. It is pertinent to note that the printing premise or printing room should be dust and pollutant free and clean.
d) Curing
After the image is printed, the base material is carefully removed from the board and placed into the box oven for curing. If the ink isn't cured to the right temperature, the ink may crack or come off the base material. This is a critical part of printed to ensure the customer a long lasting product
IV. Testing:
The printed RFID label antenna is tested for the open circuit and contact resistance. There should not be any open or short circuit in the printed antenna and the closed loop contact resistance should not be more than 22 ohms to 25 ohms. Once the testing is done the RFID label is given for chip bonding.
a) Track continuity:
The continuity of the conductive tracks printed is important to ensure if there are no open circuits in the antenna. If there are any open circuits observed then the contact resistance will be very high and subsequently will reduce the tag performance.
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b) Contact resistance:
The contact resistance of the conductive traces printed as the RFID tag antenna should be between 22 to 25 ohms to ensure good performance of the RFID Tag. The contact resistance can be measured using multimeter.
V. Chip bonding: -
The chip an integrated circuit is one of the components that for a RFID label or tag. The chip is bonded to the RFID label antenna at designated locations. The chip is bonded to the RFID label antenna pads using the silver conductive epoxy.
Following are the advantages of using the Printing Technology for laying the RFID label antenna:
1. The material cost of the inks used is much lower than that of the traditional stamped or etched antennas
2. Since high speed printing processes are both fast and additive, applying a conductive ink antenna is significantly cheaper and faster than other alternatives.
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