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MEMS milliactuator for hard-disk-drive tracking servo

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4 Author(s)
Hirano, T. ; Almaden Res. Center, IBM Corp., San Jose, CA, USA ; Long-Sheng Fan ; Gao, J.Q. ; Lee, W.Y.

This paper describes the design, fabrication, and operational characteristics of a MEMS milliactuator designed for servo tracking in a hard-disk drive (HDD). The actuator is designed to increase the bandwidth of an HDD tracking servo and pack more recording tracks on a disk. An Invar (low thermal expansion metal) electrode position process was developed to meet the thermal stability requirement. The electroplated Invar's thermal coefficient of expansion is as low as 6.3×10-6/K, which is almost half of that of pure nickel. For the plating mold pattern definition, a high-aspect-ratio polymer etching technique was developed. A high-aspect-ratio structure line-and-gap definition is required to achieve both a high directional stiffness ratio and electrode efficiency for the actuator. The etching technique described can etch through a thick (<40 μm) polymer layer with an aspect ratio of 16:1 at an etch rate of <2 μm/min. Low-cost/high-volume manufacturing is achievable by this batch fabrication technique. A milliactuator was fabricated and assembled with a suspension and a slider weighted at around 2 mg. The slider was successfully driven by the milliactuator while the slider was flying on a spinning disk. The operational characteristics (frequency response) of the in-flight milliactuator were measured, and the results indicate that the actuator is suitable for high-bandwidth HDD servo-tracking applications

Published in:

Microelectromechanical Systems, Journal of  (Volume:7 ,  Issue: 2 )