Modification for the Mechanical Model of Flex Cable in Hard Disk Drives With an External Electric Field

Abstract

The demand of raising recording density for hard disk has increased these years to achieve higher storage capacity of hard disk drive. This promotes the diminution in track size of hard disk nowadays to only hundreds of nanometers. Thus, more precisely-operated and robust actuation system for read/write heads in HDDs has been the research and development focus. Among mechanical contributors, Chang [1] indicated that flexible circuit in HDDs has been found to be a problematic vibration source that can interfere and reduce the operation accuracy of read/write arm. To perfectly eliminate the dynamic responses of flex cable, piezo-electric (PZT) film was adopted by attaching it onto flex cable to achieve the goal of vibration control. When an external electric field is applied to this PZT film, piezoelectricity effect is then taken place which results in induction of mechanical shear force in flex cable. The cable’s vibrations can then be controlled by this mechanism with the additional PZT film on the flex cable. With energized PZT film, this means that flex cable will turn harder and its stiffness will become larger, which makes the dynamic behavior of flex cable becomes an uncertainty. The mechanical model built in previous work [2] then fails to predict the dynamic response of the flex cable. Due to the problems mentioned above, modification for the mechanical model is imperative and it was elaborated by considering the shear effects produced by PZT in this paper. As reported by Kenji Uchino [4], Henno Allik [5] and many other researchers [6–8], finite element methods have been applied to many piezoelectric applications. Piezoelectricity includes electrical and mechanical behaviors of a material. Therefore, the piezoelectric constitutive equations were conducted in this paper to consider this combined electroelastic effects from PZT.