FPCB Masked One-Step Etching Large Aperture Mirror for LiDAR

Abstract

This paper presents a Flexible Printed Circuit Board (FPCB) masked one-step etching large aperture mirror for Light Detection and Ranging (LiDAR). A FPCB structure is bonded on a thin silicon wafer ( $50\sim 200~\mu \text{m}$ thick) coated with a 100 nm thick metal film and one-step of DRIE is used to etch the wafer with the FPCB structure as the mask and the metal film as the stop layer. The simple fabrication process and 0.1 mm (instead of $ needed for microfabrication) resolution photolithography lead to a very low cost of a few dollars. Copper coils embedded in the FPCB structure are attached to the backside of the large aperture mirror plate, instead of beside the mirror plate as the case in MEMS magnetic mirrors, to generate a high magnetic force and achieve a relatively high frequency considering the large aperture and high thickness. Modeling and prototyping of two designs, Mirror_A and Mirror_B, are presented to verify the novel mirror technology. LiDAR applications of the novel mirror technology are demonstrated and tested. Achieved performances are: Mirror_A, aperture $12 \times 12$ mm, oscillation frequency of 510 Hz, field of view (FOV) of 30° and radius of curvature (ROC) of 10 m; Mirror_B aperture $24 \times 24$ mm, oscillation frequency of 160 Hz, FOV of 20° and ROC of 10 m. [2020-0085]