Disk Flutter in Helium condition

Abstract

For high capacity hard disk drive (HDD), Helium is widely used to reduce disk flutter which deteriorate positioning accuracy largely. In order to know Helium effect, we studied disk flutter in Helium condition using laser doppler vibrometer (LDV). In this paper, we changed Helium density, pressure and disk thickness, and then measured disk flutter. The magnitude of disk flutter was inversely proportional to the disk stiffness. And disk flutter was well described by Reynolds number, suggesting disk flutter is excited by fluid force. The result showed not only Helium density but also low pressure is effective for positioning accuracy due to disk flutter.