INTEGRATED, VARIABLE-RELUCTANCE MAGNETIC MINIMOTOR

The use of lithography and electroplating to fabricate variable-reluct ance, nearly planar, integrated minimotors with 6-mm-diameter rotors o n silicon wafers is described. The motors consist of six electroplated Permalloy(R) horseshoe-shaped cores that surround the rotor. Copper c oils are formed around each core. The Permalloy and copper electroplat ing baths, electroplating seed layers, and through-mask plating techni ques are similar to those used to fabricate inductive thin-film heads. High-aspect-ratio optical lithography or X-ray lithography was used t o form the various resist layers. The rotors were fabricated separatel y, released from the substrate, and then slipped onto the shaft, which was plated as part of the stator fabrication process. The fabrication processes for stator and rotor are described in this paper, and initi al minimotor operation data are presented.