A Flip-Chip Alignment System With the Property of Deviation Self-Correction at the Nanoscale

Abstract

Alignment system, with large stroke, high accuracy, and deviation automatic correction properties, is really attractive for performing the task of wafer-level flipchip packaging. The motivation for this work is enabling a common packaging system to run in a manner of deviation automatic correction. To this end, in this article, three parallel kinematic flexure limbs with lever displacement amplifier are designed to construct a 3-RRR (R is revolute) XYθ deviation corrector. After a series of kinematics theoretic analyses and dimension optimizations, the mechanism is evaluated. Given the dynamic coupling linear and angular motion of the corrector are hard to be acquired simultaneously by common commercial displacement sensors, a “coarse-precise” composite visual inspection algorithm is designed to capture the precise motion in XYθ directions at the same time. Then, a series of validation experiments are successfully carried out, including visual inspection test, kinematics characterization, open-loop and closedloop tracking tests, and flip-chip deviation correction test. The results indicate that the resolution and the absolute positioning accuracy of the developed alignment system are achieved up to 40 nm/10 μrad and 0.3 μm/30 μrad, respectively, and the positioning period under maximum range is kept within two control cycles (0.7 s). Finally, in association with the deviation corrector, the accuracy of the alignment system is improved up to 0.3 μm/0.03 mrad, which proved that the proposed strategy provides an effective solution for the one-step accurate alignment operation of advanced chip packaging.