The hottest screen printing and RFID antenna manuf

Printing and RFID antenna manufacturing

the loop antenna made by printing or gravure printing and then etching is an indispensable part of RFID, so the development of RFID is also driving the development of RFID loop antenna. The author recently contacted most domestic RFID loop antenna manufacturers and sent 1 Selection of friction coefficient in printing active printing film coil now the era of manufacturing loop antenna with 0.013 mm thick copper wire has passed. The era of using PET or PP as the base material and covering copper foil on both sides also disappeared last year (this is because the copper price rise is too large for manufacturers to bear). Now the most popular method is to use pet or PP as the base material and bond 0.025 ~ 0.076 mm aluminum foil on both sides, then gravure the mask pattern (antenna pattern), and finally etch. In April, 2006, at the IC exhibition held in Haidian gymnasium, I got a sample of Tsinghua unisplenum RFID antenna with chip. The antenna is printed with silver paste. This sample probably marks the direction of our manufacturing RFID antenna. Recently, many manufacturers and friends who are preparing to produce RFID called me to discuss whether the price of silver paste still rises and whether copper paste can replace silver paste for the printing of R high-rise building glass FID antenna. It is not difficult to see that they want to use the method of printing silver paste directly to complete the manufacture of the antenna. I think this is a great leap. First, it greatly shortens the production process, speeds up the production cycle, and eliminates environmental pollution and health hazards to operators

rfid antenna manufacturing process and status quo

1 Wire binding era

most of the earliest rfid antennas were made with 0 It is made of 0.13 ~ 0.025 mm copper wire (the copper wire has an insulating layer), which is feasible in large objects or chassis, but limited in small chassis

2. Printing pattern etching method

in order to reduce the volume of the antenna and paste it on the plane, copper foil is coated on the surface of the insulator (sheet). Then use the anti-corrosion ink to make the pattern, remove the ink and wash after etching, and finally cut it into shape. This process can meet a certain batch production, but the cost is high. In addition, this kind of antenna is double-sided, which is more complex to process, and it was soon replaced by the following methods

3. Gravure pattern etching method

double sided aluminum foil coated double-sided gravure corrosion resistant pattern double-sided U V curing double-sided etching double-sided film removal. The whole process above is shaft to shaft production, some are connected into lines, and some are carried out in sections. At present, this method is mostly used to manufacture rfid antennas at home and abroad. Its outstanding advantages are fast speed and high output

4. RFID antenna is manufactured by printing conductive paste

this method uses conductive paste to replace aluminum foil or copper foil wires

there are two methods: printing and gravure printing

1) printing conductive paste

(1) version manufacturing: no matter what method is used to manufacture the version, the first requirement is to have the best printing resistance. The second is to determine the thickness of the plate pattern according to the thickness of the conductive layer of the RFID antenna. Here, it is proposed that the thickness measurement should be carried out after the printed antenna pattern is cured, so as to maintain the uniformity of the thickness and the consistency of each piece. Finally, test the square resistance value, and confirm the process parameters after the square resistance value is controlled within the allowable technical range. In addition, if the indirect method is used, the consumption factor of diaphragm thickness should also be considered

(2) printing: automatic or semi-automatic printing machines are mostly used, and the way of feeding and outputting materials is shaft to shaft. The most important thing in this process is not to shut down, so production should be carried out in a clean environment. In order to make production uninterrupted, it is best to install a set of automatic inking system and bilateral ink return plates on the plate (the function is to make the ink that extends out of the edge fall into the middle of the figure every time the ink is scraped, and then scrape again after ink return), so as to prevent the ink from extending to the edge, resulting in solvent volatilization and viscosity change. The purpose of installing an automatic inking system is to maintain the consistency of ink viscosity and the uniformity and consistency of scraping. In addition, once confirmed, the hardness, running speed, printing angle, distance and other parameters of the rubber scraper cannot be changed at will

pay attention to the matching between the rise and fall of the plate and the feeding and discharging speed. Generally, the cycle of feeding, printing and discharging is about 7 ~ 10 s. only at this speed can a certain amount be completed

although this method of printing conductive paste can complete a considerable batch, it is only limited to one side, and it is more troublesome in the production of two sides, because it is difficult to align and coincide; The winding tightness cannot be controlled, and the error is too large. If it is a full-automatic double-sided printer (special automatic line), the situation is completely different, and the problems encountered in the previous manual or semi-automatic can be solved (a certain number of companies have introduced or are introducing this kind of automatic line)

2) the difference between gravure conductive paste

and the above conductive paste is only the difference of printing method. In India, the manufacture of the plate has a certain impact on the thickness of the antenna pattern; In gravure printing, the depth of gravure roller graphics is also a factor that determines the thickness of the ink layer. However, there are two methods in the manufacture of gravure roller graphics: laser engraving and traditional plate making. The former can process the groove of the graphics more accurately (referring to the depth of the groove and the width of the line), provide more accurate values in the operation of the subsequent process, and can well control the thickness of the ink and master the salivation of the ink. Relatively speaking, gravure conductive paste is a better way to manufacture RFID antenna, which is characterized by accurate graphics, uniform thickness, and printed graphics that can meet the electrical performance requirements

3) calculation and cost of square resistance of conductive paste

many people think that it is OK to measure the resistance of the conductor by viewing the reading of the dial according to the two poles of the three-way meter. 3. When installing, the two ends of the cutting rod are in contact with each other. Although this method is feasible, what we require is the volume resistance, which is directly related to the thickness, length and width of the paste we print, The current international standard is the square resistance value: (/□) that is, the resistance of any opposite side of a cube with the same thickness is the square resistance value of the conductor

recently, many foreign and domestic companies have launched conductive silver pastes for rfid antennas. All reports say that their pastes have the smallest resistance value, delicate and stable, but how small is the resistance value? What is the post printing cost of RFID antenna? We must do an in-depth study and test to have an answer: one company, for example, said that the resistance value of their silver paste is 40 when it is 0.4 mm wide, 1.4 m long and 5 m thick. After calculation, the square resistance value is only 0.011/mouth, which shows that the silver content in the silver paste is more than 51%, and the domestic price of this kind of silver paste is 200 ~ 3000 yuan/kg. Then what is the paste used for each antenna? It is about 2 g, and the price of each antenna is a few yuan (here refers to the material cost). From the above calculation, it is not difficult to see that the cost of using this slurry is still very high

we saw in the report that DuPont's special paste, the domestic paste, a kind of conductive ink newly invented in South Korea to print on the paper surface to complete the manufacture of the antenna, the direct printing system developed by Manroland, and the print used for RFID to help consumers judge the opening time of perishable food and products. In these encouraging reports, No one said what products they used to make cars more energy-efficient materials and technologies, which companies have been used in production, and no one calculated the cost

in today's commodity economy society, commodities are composed of their own quality and cost, both of which are indispensable and interact with each other. For example, when Haier air conditioner enters Wal Mart supermarket, can the RFID tag used be the same as the tag price of a bottle of shampoo? Similarly, can an ordinary commodity have the same label as the wagon of the same train? Developed countries in the world are testing the low-cost label of 5 cents for single daily necessities and food. Obviously, this price is unacceptable in China. In short, if the price of conductive silver paste in China cannot be reduced, or there is no suitable substitute, the label cost of RFID cannot be reduced. For cost, RFID antenna manufacturers must first be familiar with the technical requirements of the order, which mainly come from two aspects: first, the length, width and wire thickness of the graphic antenna; Second, the required and allowable resistance value of such a long wire can be calculated by selecting the square resistance value of the conductive paste through calculation

three elements of modern RFID antenna manufacturing

the three elements of manufacturing RFID antenna are: printing (gravure printing), curing (drying), and winding

1. printing (gravure printing), which has been described above

2. curing (drying)

1) in the process of gravure anti-corrosion ink, some factories have both UV curing and IR curing after gravure printing, because the ink used needs both UV curing and IR curing. Through nearly two years of investigation, it is found that this is wrong for the following reasons: (1) waste of energy; (2) Solvent volatilization pollutes the environment; (3) Tedious processing; (4) Cause trouble to the post process (it is difficult to fade the ink); (5) The quantity of waste products increases. After our efforts, the IR curing system has been removed from relevant factories, which has greatly improved their production appearance, not only saving energy, reducing costs, but also increasing the yield

when printing or gravure conductive pastes, they are IR cured. At this time, the selection of conductive pastes is very important, especially the selection of appropriate curing equipment. In the IR curing system, the saddle shaped heating curve should always be maintained. Therefore, in order to achieve complete curing in a short time, the main method is to increase the length of the drying channel, so that the baked antenna paste can have a longer curing time. The method of testing the complete curing is very simple. As long as the fully cured antenna is placed in an environment with a relative humidity of 85% - 90% and maintained for 24 hours, the resistance value can be tested, which is no more than 10% (the test here is a self-test in our own production, so as to master the curing law, and the standard test should also be in accordance with the national standard)

I think the best curing method is to apply high infrared technology, which not only saves energy, but also covers only 1/5 of the area of ordinary IR drying channel, and the curing time can be shortened to more than ten seconds. Its characteristic is that the starting time is short, and the temperature can rise to the required value after 1 min of power on. Because the high infrared technology is full band, it can instantly cure the inner and surface layers of the ink at the same time, which solves the problem of incomplete curing of the inner and bottom layers. The specific comparison is as follows: the comparison between ordinary IR curing line and high infrared in the mode of shaft-to-shaft transmission (Table 1 is the comparison in the case of using the same conductive paste)

this high infrared technology can well solve the bottleneck problem of conductive paste curing in production. It has been promoted in other electronic industries, and recently in