Hybrid micro assembly of microchips on segmented patterns

This paper reports a novel process that positions RFID chips on segmented artificial antenna pattern using hybrid assembly technology. A droplet of water is firstly dispensed to an artificial pattern composed of four pads. Then a 730×730μm RFID chip with four bumps of 20μm in height is released onto the artificial pattern using a robotic microgripper. Finally the RFID chip is self-aligned with the outer edge of the pattern due to the surface tension of water. The artificial antenna pattern is designed to have four pads on the substrate to mimic the shape of the real antenna with four electric or mechanical connections. The pattern is hydrophilic, while the rest of the substrate is hydrophobic. A series of experiments have been carried out to understand the influences of the hydrophobic gap to the result of self-alignment, as well as to clarify the influence of dispensing position and releasing bias to the result of self-alignment. The result indicates that RFID chips can be reliably assembled on the segmented pattern with 50 μm and 100 μm gaps, and the assembly is also possible with larger gaps. There is also no obvious influence towards the assembly results by choosing dispensing water to the releasing position or dispensing water to the center of the antenna. Furthermore, the experimental results show that the self alignment between the RFID chips and the pattern occurs reliably when the releasing bias between the RFID and antenna is less than 300μm for patterns with 50 μm and 100 μm gaps.