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|Handling technology for 0.075-square mm powder IC chip|
|Keywords: water-based chip handling, micropipette manipulation, self-aligned positioning|
|We have developed a packaging technology for powder IC chip of 0.075-square mm × 7.5 μm thickness. The chip, which can be embedded into papers, is expected to be a key device in pioneering new markets, where it can cheaply and easily manage a number of articles and identify papers such as securities. Manipulating a fine chip in a dry environment has been difficult due to adhesion of the other chips and scattering from the influence of electrostatic phenomena. However, using the micro-bead and cell trapping technology used in cutting-edge biotechnology, it is possible to put the chips on a substrate one by one free from the influence of electrostatic phenomena. The technique uses a double-surface-electrode chip, and a novel water-based chip handling technique composed of a micropipette manipulation and a self-aligned positioning. The double-surface-electrode structure that has two individual surface electrodes is advantageous in that when mounting the powder chip on a substrate, the chips are placed on the substrate without the need for highly accurate positioning, including the chip orientation control (upside-down, rotation). As for the micropipette manipulation, the chips are kept dispersed by stirring liquid with addition of a 0.5% surfactant to prevent chips from sticking together, and a flat-end glass micropipette successfully captures a single chip with an ideal orientation. The self-aligned positioning of the chip uses micro liquid droplet shrinkage and evaporation phenomena. The chip is able to move together with the droplet edge, and is positioned in the predefined hydrophilic domain. The liquid cushioning pick-up and placing action enables stress-free handling. The technique will contribute to the progress of water-based thin-chip assembly used to develop robust, inexpensive instruments.|
Hitachi, Ltd., Central Research Laboratory