Japan's National Institute of Advanced Industrial Science and Technology (AIST) has developed a method which can drastically reduce the electrical resistance of antennas, wirings etc., of radio frequency (RF) ID tags formed by screen printing. This method is one where, after printing the antenna and wiring with metallic inks, a pressure annealing process is applied to them without high temperature baking. Using this technique, we have succeeded in fabricating RF ID tags on flexible substrates entirely by printing. This indicates that high-sensitive RF tags can be formed on flexible substrates such as plastics entirely by printing, and thus a further reduction in the cost of the tags can be facilitated. This will induce the acceleration of widespread use of the tags.
RF ID tags are terminals which give and receive information by RF signals, by which existence of and information about objects can be recognized and administrated. Because of their convenience, widespread use of the tags is expected, but their high manufacturing cost is an obstacle at present. Thus the establishment of low-cost fabrication techniques of the tags is urgently needed. Techniques for fabricating the tags entirely by printing have been investigated to resolve this problem, but none have been established yet.
We have developed a "pressure annealing" technique to reduce the resistance of conducting circuits formed on plastic film substrates by printing, without high temperature baking. Antenna circuits created by this method showed a sensitivity similar to that of antennas produced by a commercial vacuum processing technique. Moreover, using our technique, we have confirmed that RF ID tags fabricated entirely by screen printing, applying our technique, can work well at frequencies of 5-40 MHz.
The pressure annealing method is applicable to the fabrication of the wirings and electrodes on flexible substrates, such as plastic films, by printing, because even if the baking of conducting inks is done at temperatures below 200°C, their resistance can be sufficiently lowered. We expect that the method developed may be applied for various devices to manufacture low-cost, flexible ubiquitous information terminals.