A novel Si micromachined moving-coil induction actuated mm-sized resonant scanner

Abstract

A novel silicon micromachined moving-coil scanner with electromagnetic induction actuation principle is presented. It was manufactured by the Si-LIG process, silicon-lithography-electroforming (Galvanoformung, from German), where its mechanical structure was made by bulk silicon micromachining of 200 µm thick (1 0 0) silicon substrate, and its armature was patterned by deep UV lithography and Au electroplating. The monolithic mechanical structure is a 12 × 24 mm2 rectangular frame connected by 4.5 mm long torsion bars to a 4 × 10 mm2 rectangular rotor. On one face of the rotor is the armature, a 70 µm thick, single turn, electroplated Au coil with 3.3 mΩ electrical resistance. The other face of the rotor was mirrored by a 1480 Å thick Al film. An external magnetic circuit generated a constant 0.115 T magnetic field parallel to the coil plane and a 0.01 T (peak value) field normal to the coil plane. A maximum mechanical deflection angle of 9.0° pp at the 1311.5 Hz resonance frequency was measured, and a quality factor, Q, of 347 was achieved in air. A mathematical model for the device was derived and a dimensioning procedure was developed. The results show that electromagnetic induction actuation is adequate for mm-sized systems and capable of producing resonant scanners with performance compatible with applications such as bar code readers.