MEMS Air-Damped Isolator for Dual-Axis Micromirrors: Broad-Range Frequency Vibration Isolation

The fracture failure of dual-axis micromirrors under the AEC-Q100 qualification test could not be mitigated by structural designs alone due to the need for compatibility in bending and torsional stiffness. To address this, a passive MEMS vibration isolator was proposed to protect the micromirrors within a broad frequency range of 20 Hz to 1200 Hz, unlike conventional designs limited to a fixed frequency. The proposed method was based on a two-degree-of-freedom (DOF) micromirror-isolator system, in contrast to the single-DOF systems employed in existing methods. The isolator’s stiffness was matched to the micromirror’s stiffness to maximize the mirror plane’s movement, and an air damping mechanism was incorporated using a $20~\mu $ m gap to control the dynamic response time. The designed isolator was fabricated using a novel SOI-on-glass process and tested on a high-precision vibration shaker equipped with a laser Doppler vibrometer. Results showed that the proposed isolator attenuated vibration amplitude by 25.55 dB, closely aligning with the design value of 24.89 dB. Additionally, an automotive-grade vibration test demonstrated successful isolation under a 50g vibration within the 20 Hz to 1200 Hz frequency range, without introducing parasitic modes that could disrupt the micromirror’s operational modes.[2024-0220]