A Monolithic Force Sensing Integrated Flexure Bonder Dedicated to Flip-Chip Active Soft-Landing Interconnection

A flip-chip bonding system has a high demand for both force sensing and control functions to ensure the high-quality chip interconnection. The motivation of this article is to combine the ability to enable a common flip-chip bonding system to run in the manner of active soft-landing (ASL) interconnection. The developed flexure bonder achieves these functions by designing a flexure force sensing and control mechanism integrated with strain gauge sensing and piezoelectric actuating functions. First, the design, modeling, and optimization of the flexure mechanism are presented. Theoretical analyses, including force sensing and control working principle demonstration, force-strain model derivation, and dynamics response modeling, are carried out. Besides, aiming at highly sensitive force control under high-dynamic working condition, the mechanism is optimized by the multiobjective genetic optimization algorithm. Then, this flexure bonder mechanism is analyzed and evaluated by finite-element analysis. Finally, a series of validation experiments, including force sensing calibration and performance tests, open- and closed-loop force controlling tests, ASL tests, and actual bonding tests, are successfully implemented. The results indicate that the operation accuracy of the developed system is improved up to +/- 1 N under 400-N range, and the overshoot of ASL is less than 2 N under 6000-N/s loading speed. All the results uniformly confirm that the proposed bonding system can achieve precise force control and satisfactory chip interconnection performance with the proposed ASL bonding strategy.