A MEMS Voice Coil Motor with a 3D Solenoid Coil

Previously-reported electromagnetic (EM) linear micromotors typically applied meander coils or planar spiral coils because there are many difficulties in solenoid coil fabrication using integrated micro electro-mechanical system (MEMS) technologies. However, solenoid microcoils with iron cores have a higher inductance density and a lower leakage magnetic flux than planar coils. In this study, a MEMS voice coil motor (VCM) with a 3D solenoid voice coil was designed., fabricated and tested. The VCM was comprised by a voice coil fabricated using MEMS processes as the traveler and a combination of two permanent magnets (PMs) and an E-shape silicon-steel core which was inserted into the voice coil as the stator. The copper voice coil in silicon substrate was a solenoid-shape coil of high aspect ratio (coil height was 1.4 mm and line width was 0.1 mm). The coil was embedded tightly in the silicon substrate, resulting in a good heat dissipation performance and thus a high current-carrying capacity. The VCM weighed 0.07 g with a size of approximately 4 mm x 2.5 mm x 4 mm before circuit connection. The testing results showed that the effective travelling distance of the traveler was 1 mm with stable thrust force of approximately 3.9 mN/A and the motor vibrated stably when a 50 Hz square-wave current of 0.5 A was applied. This MEMS VCM has low weight and high thrust force, which has bright application prospects in micro actuators.