Detailed RFID technology and its new label production process (II)

1. Traditional manufacturing process of tag antenna

1). Processing the label antenna by etching

The antenna should be printed with a resist film before etching. First, the PET film sheet is coated on both sides with a metal (such as copper, aluminum, etc.) foil; then printed (screen printing, gravure, etc.) or photolithography. The resistive ink is printed on the double-sided antenna pattern area of the substrate to protect the circuit pattern from being etched during etching: then etching is performed, that is, the printed ink pattern cured sheet is immersed in the etching solution to dissolve the unprinted resist ink layer. The metal of the area; then the anti-etching ink on the metal layer of the film sheet antenna pattern is removed, thus obtaining the tag antenna. Alternatively, a photoresist film is preliminarily coated on the surface of the copper-clad substrate by photolithography, and exposed by a corresponding mask, and subjected to development etching to remove the residual resist film on the plate to obtain a complete antenna pattern.

2). Winding method for preparing tag antenna

Currently. The manufacturing process of the copper wire-wound RFID tag antenna is usually carried out by using an automatic winding machine, that is, directly coating the base carrier film with an insulating varnish and using a low-melting-painted copper wire as a substrate for the RFID tag antenna. Finally, the wire is mechanically fixed to the substrate with a binder. This method is highly reliable, but it is too costly for RF19 electronic tags.

2. Label antenna printing process

Based on the disadvantages of the polluted environment and high cost in the traditional tag antenna preparation method, and the process is complicated, the finished product is produced for a long time and will be replaced by a new process. Direct printing of RFID tag antennas by printing is an environmentally friendly, energy-saving, low-cost manufacturing process. Existing possible printed RFID tag antennas are available in both screen and inkjet printing.

1). Screen printing method to prepare antenna

Screen printing is a process of direct printing using a stencil, that is, direct printing on a paper-based or plastic film web with a conductive ink. The general process flow is:

The screen printing of the tag antenna is to press the conductive ink from the other side of the screen to the screen through the squeegee, and the ink penetrates the mesh gap of the antenna pattern on the screen, and is printed on the printed On the substrate. When RFID tag antenna printing is performed, the antenna coils of RFID tags with different operating frequencies will correspond to different turns, the thickness of the coil and the distance between each turn (for example, the chip using 13.56 MHz in the HF band, usually it requires a coil The number of turns is 6, the thickness is about 20um: UHF band uses 868MHz and 950MHz chip, the thickness of the coil section is about 4um), so the thickness of the printed ink layer, the width of each line and the contour of the dried figure are strict. The tolerance range (such as the error of two overlapping overprints must be within 0.1mm).

The thickness of the ink layer printed on the screen can be up to 100um, which is several times that of flexo, offset and gravure, which is very advantageous for printing the tag antenna with conductive ink. In the actual production of printed circuits, the thickness of the ink layer is generally 8 to 12 um, and the drying can be accomplished by means of UV, IR and hot air.

2). Inkjet printing method to prepare antenna

Screen printing saves cost to a certain extent, but its ink uses about 70% high-silver conductive silver paste to obtain an antenna between 15 and 20um. It is a thick film printing method with high cost and has printing process. Solvent discharge, ink layer flexibility is poor. The conductive circuit is prepared by using an inkjet printer, and only the pattern designed by the computer system is required to spray conductive ink onto the substrate by the nozzle of the inkjet printer to form a conductive line. As an unconventional printing method, the inkjet printing method has been widely concerned in terms of antenna fabrication due to its short manufacturing cycle, no pollution, and low cost. Many well-known institutions and research institutes at home and abroad have long been committed to the research of inkjet conductive inks and have made remarkable achievements. Beijing Institute of Printing, with the research team led by Prof. Li Luhai, successfully developed an inkjet conductive ink with a conductive film thickness of about 1 μm and a resistance of about 1 Ω. In 2008, Kovio introduced a FFD prepared by inkjet printing nano-silicon ink. , the first commercial success of inkjet printing ink; South Korea's Suncheon University in 2009 developed a full-print 1-bit RF tag based on carbon nanotube ink.

The use of inkjet printing for RFID tag production can be divided into three ways:

(1). Using inkjet printing method to spray resist ink, solder resist ink and character ink onto the copper clad plate, and after curing, obtain the finished product;

(2). Using a conductive ink containing nano metal particles, the circuit pattern is directly sprayed on the polyester substrate, and cured at a low temperature to form a circuit:

(3). By using ink of the corresponding characteristics, inkjet printing methods are used to manufacture electronic components such as capacitors and resistors in RFID tags. Compared with traditional printing methods. Inkjet printing can achieve faster production speeds, lower printing costs, and more importantly, increase the wiring density to improve the quality of the finished product.

Outlook:

RFID tags are gradually being applied in various fields due to their unique advantages. People are committed to research and solve the shortcomings of traditional preparation methods. Inkjet printing, as a new technology of tag antenna, relies on the advantages of low cost, good conductivity, no pollution and easy control of antenna patterns, which will make RFID technology more widely used.