Simulation and Experimental Analysis of Contactless Chip Pickup Process Based on a Vortex Flow Gripper

As the preceding process of chip-to-wafer (C2W) hybrid bonding, die pick-up, and transfer are critical in 3D heterogeneous integration (3D HI) technique. Especially, with the ever-shrinking die thickness and ever-increasing bumps on the die surface, mechanical scratches and electrostatic interference on chips caused by the traditional contact-type pickup process cannot be tolerated. Therefore, it is the trend to implement contactless pickup head to realize damage-free chip transfer. Herein, a contactless, pneumatic pickup head based on vortex flow was designed for the efficient and contactless grab of $50~\mu $ m ultrathin chips. A baffle structure on the four corners of pickup head was designed, which can achieve stable noncontact pickup of target chip and maintain the position under multiangle loading conditions. Furthermore, we optimized baffle structure to reduce the oscillation of the chip by more than 50%. We explored the underlying mechanism of pneumatic noncontact pickup through computational fluid dynamics (CFD) simulation by three turbulence models. Further, a high-precision vortex platform was built to investigate the pickup force characteristics, radial pressure distribution, and oscillations for different intake pressure and their influence on the noncontact pickup effect. Eventually, the simulation and experimental results indicate that the optimal intake pressure for stable non-contact pickup is between 20 and 30 kPa. This study provides design and optimization methods for stable noncontact picking of microchips, offering theoretical and experimental basis for selecting the optimal air intake pressure in practical applications.