NDSU Researchers Develop Method for Embedding RFID in Paper
The North Dakota State University group claims that its laser-based RFID inlay assembly method can be used to inexpensively incorporate tags into paper items, such as tickets and banknotes.
Feb 27, 2013—Researchers at North Dakota State University (NDSU) have developed a method for embedding ultrathin passive radio frequency identification chips on paper or other flexible substrates. This method, the team reports, could enable the production of RFID-enabled paper at a cost lower than that pertaining to traditional RFID tags. The group is now seeking manufacturing partners to help commercialize the technology.
The process, known as Laser Enabled Advanced Packaging (LEAP), involves silicon chips so thin that they would not be detected when embedded in a piece of paper. The chips, along with antennas, are joined on a substrate at high speed, using a low-cost laser technology. Products that the method could create include security and financial paper, such as banknotes, legal documents, tickets and smart labels—all of which could benefit from having the RFID technology built into them, by proving an item's authenticity, and thereby preventing counterfeiting.
While there are RFID-based paper solutions on the market, says Val Marinov, an associate professor at NDSU and the head of the LEAP project, most RFID chips are not thin enough to be integrated into paper without either requiring the paper to be thicker than desired, or creating a bump on its surface that could interfere with printing. To be embedded in an average piece of paper without creating a significant bump, he explains, the technology would require a chip that is 20 microns (0.0008 inch) or thinner. "Thinner also means more reliable," Marinov says, adding, "At such small thicknesses, the silicon—which is otherwise a very brittle material—becomes flexible and capable of extreme bending."
Currently, Marinov says, few RFID chips are that thin, and the methods to assemble them into tags or paper are limited. Traditional pick-and-place solutions lack the speed or precision required to assemble the chip on a substrate at a low cost. When the chips are small enough, the gravitational force exerted on them is limited, and surface forces of attraction—such as static electricity—can thus make it difficult to release the chips. As such, contact assembly methods, such as the pick-and-place approach, fail as a high-precision, high-volume solution for ultrasmall, ultrathin chips.
Therefore, the NDSU researchers have developed a process for assembling ultrathin, ultrasmall chips, and have built a prototype of a solution capable of embedding ultrasmall RFID chips onto a paper substrate. The system employs a plasma etcher to thin silicon wafers down to size, if necessary, and to cut the wafers, as well as a laser beam to transfer each chip onto a substrate.
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