Detailed explanation of RFID technology and its new label production process

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Detailed explanation of RFID technology and its new label production process [Copy link]

In the early 1940s, the improvement and application of radar gave birth to radio frequency identification (RFID) technology. After a long period of exploration, RFID has now played a pivotal role in public safety, manufacturing, logistics management and other fields. Detailed explanation of RFID technology and its new tag production process DRID Radio frequency identification (RFID, RBdio Frequency Identification) technology is a non-contact automatic identification technology. It automatically identifies the target object and obtains relevant data through spatial coupling (alternating magnetic field or electromagnetic field) to achieve the purpose of target identification and data exchange. The identification work does not require human intervention. The basic working principle of the AFID system can be explained by Figure 1: the signal to be sent by the reader is encoded and loaded on a carrier signal of a certain frequency and sent outward by the antenna. The electronic tag entering the reader's working area receives this pulse signal. The relevant circuits in the chip in the tag demodulate, decode and decrypt this signal, and then judge the command request, password, authority, etc. If it is a read command, the control logic circuit reads the relevant information from the memory, encrypts, encodes, modulates, and then sends it to the reader through the antenna inside the electronic tag. The reader demodulates, decodes, and decrypts the received signal and sends it to the central processing system for relevant data processing; if it is a write command to modify information, the internal charge pump caused by the relevant control logic increases the working voltage and provides the content in the EEPRQM for rewriting. If it is determined that the corresponding password and permission do not match, an error message is returned. Scope of application of RFID system The era of the international Internet of Things is coming. It is reported that RFID technology has been widely used in the European and American markets. With the increasing maturity of RFID technology in the Chinese market and the reduction of RFID tag prices, RFID electronic tags will replace traditional one-dimensional barcodes and two-dimensional codes. If the two-dimensional code is an extension of the one-dimensional code label, then the birth of RFID is a revolution in the label industry. Its application areas are mainly in the following aspects: 1. Logistics management Logistics is the largest market application space for RFID, which can greatly improve the efficiency of logistics links and provide technical support for achieving zero inventory. Global retail giants Wal-Mart and Germany's Metro have vigorously promoted the application of RFID tags, and have both used RFID technology in supermarkets to achieve product identification, anti-theft, real-time inventory and product expiration control. 2. Food safety Food safety is a major issue for the people's livelihood of a country. RFID technology can ensure food safety in all aspects by managing and recording the original planting or breeding process of food and forward tracking and reverse tracing of the food circulation process. 3. Commodity anti-counterfeiting Commodity anti-counterfeiting can ensure normal market order and consumer reputation, and has a huge market space. The use of RFID anti-counterfeiting technology and wireless communication networks can realize the quality inspection of commodities at any time and any place. At present, it has been piloted on tobacco, alcohol, medicine and other commodities. 4. Application in other fields RFID has a very wide range of applications, such as in traffic management, military product management, security, animal breeding and pet management, library management and other fields, all of which have great application prospects. RFID tag antenna preparation technology The core issues affecting the promotion of RFID are chip technology and cost. As shown in Figure 2, RFID electronic tags are mainly composed of substrates, antennas and chips. The antenna layer is the main functional layer, and its purpose is to transmit the maximum energy in and out of the tag chip. Compared with traditional etching and winding methods, the direct printing method of tag antennas greatly saves costs. 1. Traditional manufacturing process of tag antennas ① Etching to prepare tag antennas Before etching, the antenna should be printed with an anti-corrosion film. First, metal (such as copper, aluminum, etc.) foil is coated on both sides of the PET film sheet; then, printing (screen printing, gravure printing, etc.) or photolithography is used to print anti-corrosion ink on the antenna pattern area on both sides of the substrate to protect the circuit pattern from being dissolved during etching: then etching is performed, that is, the sheet with the printed ink pattern solidified is immersed in the etching solution to dissolve the metal in the area where the anti-corrosion ink layer is not printed; then the anti-corrosion ink on the metal layer of the thin film sheet antenna pattern is removed, so that the tag antenna is obtained. Alternatively, photolithography is used to pre-coat a photosensitive anti-corrosion film on the surface of the copper-clad substrate, and the corresponding mask is used for overlapping exposure. After development and corrosion, the residual anti-corrosion film on the plate is removed to obtain a complete antenna pattern. ② Winding method for preparing tag antenna At present. The manufacturing process of copper wire winding RFID tag antenna is usually carried out using an automatic winding machine, that is, directly winding the insulating paint on the base carrier film, and using the copper wire with low melting point paint as the substrate of the RFID tag antenna, and finally using adhesive to mechanically fix the wire and the substrate. The process flow is shown in Figure 4. This method has high reliability, but the cost is too high for RF19 electronic tags. 2. Tag antenna printing process Based on the disadvantages of environmental pollution and high cost in the traditional tag antenna preparation method, and the complex process and long production time of the finished product, it will be replaced by a new process. Directly printing RFID tag antenna by printing is an environmentally friendly, energy-saving and low-cost manufacturing process. The existing feasible printing methods for printing RFID tag antennas are screen printing and inkjet printing. ①Preparing antennas by screen printing Screen printing is a process of direct printing using a template, that is, printing conductive ink directly on a paper base or plastic film roll. The general process flow is: Screen printing of tag antennas is to sweep the conductive ink from the other side of the screen with a scraper to press the ink across the screen, and the ink penetrates through the mesh gaps of the antenna pattern on the screen and adheres to the printed substrate. When printing RFID tag antennas, since the antenna coils of RFID tags with different operating frequencies will correspond to different numbers of turns, coil thickness and distance between each turn (for example, the HF band uses a 13.56MHz chip, which usually requires a coil with 6 turns and a thickness of about 20um: the UHF band uses 868MHz and 950MHz chips, and the coil cross-section thickness is about 4um), the thickness of the printed ink layer, the width of each line and the outline of the graphic after drying have strict tolerance ranges (for example, the error of two overlapping overprints must be within 0.1mm). The ink layer thickness of screen printing can reach up to 100um, which is several times that of flexographic printing, offset printing and gravure printing. This is very beneficial for printing tag antennas with conductive ink. In actual printed circuit production, the ink layer thickness is generally required to be 8-12um, and its drying can be completed by UV, IR and hot air. ② Preparation of antennas by inkjet printing Screen printing saves costs to a certain extent, but its ink uses a high silver content of about 70% conductive silver paste to obtain an antenna between 15 and 20um. It belongs to a thick film printing method with high cost, and there is solvent emission during the printing process, and the flexibility of the ink layer is poor. The conductive circuit is prepared by an inkjet printer. It only needs to spray the conductive ink onto the substrate according to the pattern designed by the computer system by the nozzle of the inkjet printer to form a conductive circuit. As a non-traditional printing method, inkjet printing has attracted widespread attention in antenna production due to its short production cycle, no pollution and low cost. Many well-known universities and research institutes at home and abroad have long been committed to the research of inkjet conductive inks and have achieved remarkable results. The research team led by Professor Li Luhai of Beijing Institute of Graphic Communication has successfully developed an inkjet conductive ink with a conductive film thickness of about 1um and a resistance of about 1Ω: In 2008, Kovio Company of the United States launched FFD prepared by inkjet printing nano-silicon ink, which became the first commercial success case of inkjet printing ink; In 2009, Sunchon University of South Korea developed a fully printed 1-bit radio frequency tag based on carbon nanotube ink. There are three ways to make RFID tags using inkjet printing: ① Use inkjet printing to spray anti-corrosion ink, solder mask ink and character ink onto the copper-clad board, and obtain the finished product after curing; ② Use conductive ink containing nano-metal particles to directly spray the circuit pattern on the polyester substrate, and form a circuit after low-temperature sintering and curing: ③ By using ink with corresponding characteristics, the electronic devices such as capacitors and resistors in RFID tags are manufactured by inkjet printing. Compared with traditional printing methods. The use of inkjet printing can achieve faster production speeds and reduce printing costs. More importantly, it can increase its wiring density, thereby improving the quality of the finished product. Outlook RFID tags are gradually being used in various fields due to their unique advantages. People are committed to studying and solving the shortcomings of traditional preparation methods. Inkjet printing, as a new technology for tag antennas, will enable RFID technology to be more widely used, relying on the advantages of low cost, good conductivity, no pollution, and easy control of antenna patterns.