0.075 × 0.075 mm2 ultra-small 7.5 μm ultra-thin RFID-chip mounting technology

An ultra-small (0.075x0.075-mm area) ultra-thin (7.5-mum thickness) radio-frequency identification (RFID) chip, called a "mu-chip," is expected to be adopted in applications like counterfeit prevention and product tracking of paper media and other small goods. For adoption in these applications, technology for mounting a mu-chip on an external antenna must be developed. Accordingly, we have developed a new technique for handling ultra-small mu-chips (called the "UH technique") by means of an automated apparatus. By the UH technique, the mu-chips are kept dispersed by liquid agitation, and only a single chip is captured and manipulated by micropipette. The efficiency of capturing a single mu-chip depends on the micropipette configuration, number of chips, and mu-chip stock solutions. A flat-end glass capillary micropipette with an inner and outer diameter of, respectively, 41 and 87 mum, which was treated by an optic-fiber cleaver, only successfully captured a single chip with an ideal orientation. The yield rate of capturing a single mu-chip, picked up from various types of liquid solutions, was investigated. This investigation found that a surfactant addition to the mu-chip stock solutions effectively prevented sticking between chips. In single-chip capturing performed in 0.5% NP-40, yield rate was 62%. Mounting of single mu-chips on films with constant 0.7-mm pitch was demonstrated. The time needed for an automated procedure for manipulating 100 chips was 44 min (26.4 s/chip).