Printing technology plays an important role in the manufacture of RFID tags

Printing technology is involved in the manufacture of RFID tags. This will be a very beneficial attempt. With the continuous deepening of the study of printing process parameters, the continuous improvement of the conductive ink formulation will certainly make the printing technology play an important role in the manufacture of RFID tags.

RFID tags, ie radio frequency identification tags, are a type of smart card. RFID is an identification method that uses wireless radio frequency to conduct non-contact two-way communication. It appeared during World War II, began to be used in the 70s, and began to be used on a large scale in the 1990s. Technology has been widely used in all areas of our lives, such as the most simple access cards, bus rides, and campus cards. One of the widely-recognized models for RFID technology in retail applications is the "future store" model.

In future stores, all products are tagged with RFID tags. There are two places where customers come into contact with RFID technology in stores: so-called smart shelves and smart cashiers. Smart shelves are equipped with RFID tag scanners on the shelves. They can automatically indicate that the goods are out of rack and placed in the wrong position, solve the problem of timely replenishment and correct loading of goods; there is no longer a traditional cash register in the store, but a Smart cashiers replaced. The smart checkout counter can be implemented with a screen at the exit of an RFID tag scanner. When the customer's cart passes the screen, all purchases in the car are instantly scanned, and the smart cashier automatically transfers the total cost of all the goods from the customer's credit card. This makes it easy for customers to check out and no longer needs to queue up in front of the traditional cash register.

First, the cost of RFID tags obstacles

From the above application mode, we can see that RFID tags bring us more convenient and more efficient consumer life. However, there is still a long way to go before RFID is implemented for every product. One of the bottlenecks here is the relatively high cost of RFID tags. For now, the cost of each tag has fallen below $1 to reach 20 to 70 cents. This does not matter for high-priced products, but for many low-cost products such as toothbrushes and pencils, it will be regarded as a cost barrier. Therefore, to fully promote RFID tags should reduce the manufacturing cost of tags under the premise of ensuring the performance of the tags.

Second, the advantages of printing technology in the cost of the label

RFlD tags can be divided into three major categories: passive RFID tags, semi-active RFID tags, and active RFID tags. RFID tags on retail packages are generally passive RFID, which is a passive RFID tag because it requires the reader to emit an electromagnetic signal that induces an electrical current and then emits an electromagnetic signal to the reader for tagging and reading. Information transfer between devices. The structure of this tag is generally: substrate, chip and built-in antenna (coil). At present, the manufacturing methods of coils include copper wire winding method, chemical etching method, electroplating method and direct printing method. Among these four methods, it is worth noting that the direct printing method is the most important one because it has the advantages of high speed printing of the antenna and low cost of consumables, which can significantly reduce the cost of the RFID tag.

Third, the driving force of conductive ink

Directly printed antenna technology, conductive ink is an important driving force. Without the development of conductive inks, there is no application of printing technology in the manufacture of RFID tags. Conductive ink consists of conductive particles, resins or more special raw materials, such as conductive polymers. After the conductive ink is dried on the substrate, since the distance between the conductive particles becomes smaller, the free electrons move along the direction of the applied electric field to form an electric current, which has a good conductive property, so that the ink acts as an antenna. The quality of ink is of great significance for improving the electrical conductivity and reducing the ink consumption. A good conductive ink formulation requires good printability and has the characteristics of strong adhesion, low resistivity, low curing temperature, and stable electrical conductivity after printing.

Fourth, direct printing antenna technology research

At present, the method of directly printing antenna is still in the research stage. When performing RFID tag antenna printing, the antenna coils of RFID tags with different operating frequencies will correspond to different number of turns, coil thickness and distance between each turn (eg, HF band uses 13.56 MHz chip, usually it requires The number of coil turns is 6 and the thickness is about 20μm. UHF band uses 868MHz and 950MHz chips, and the cross-sectional thickness of the coil is about 4μm.) Therefore, the thickness of the printed ink layer, the width of each line, and the outline of the dried pattern have Strict tolerance range (eg, the error of two overlapping overlays must be within 0.1 mm). When using the silk screen method to directly print the antenna, the following beneficial experiences are obtained: The hexagonal hole shape is used for the mesh, which is conducive to the complete transfer of the conductive ink; the use of solvent-based ink is better for the conductive ink; and excellent ink drying conditions are created. (For example: reducing the wind speed in the oven, the heating temperature is 140 °C, and the heating time is between 30 seconds and 120 seconds), which is conducive to the accurate forming of the printed coil pattern contour. At present, a rotary screen printing equipment company in Switzerland has created a dedicated production line for smart label printing. Stuttgart Media University of Germany in the study of gravure printing directly printed RFID tags, obtained the following beneficial conclusions: The best plate-making method is the use of diamond electronic engraving method, the resolution selected at 5080dpi. At this time, there are almost no sawtooth edges, and the necessary units can be accurately transmitted; the image file format required for front-end plate making uses a bitmap format, so that the graphic information is not easily lost; for the structure of the outlets, a special one needs to be distinguished from the traditional ones. An open network of cyberspace. If traditional cells are used, the mesh walls between the cells will divide the conductive ink and do not form a coherent path. The open cells not only retain the mesh wall but also easily solve the problem of partition wall ink. Printing technology is involved in the manufacture of RFID tags. This will be a very beneficial attempt. With the continuous deepening of the study of printing process parameters, the continuous improvement of the conductive ink formulation will certainly make the printing technology play an important role in the manufacture of RFID tags.

Reprinted from: Book Industry Forum