Performance Advances in Recording through Micro Actuation

The prerequisite for optimum recording density in hard disk storage is a minimum flight altitude and a perfect read/write head tracking. Such a read/write head contains a projectile which floats on a dynamic air bearing just above the rotating data plate and in which a thin-film read/write element is integrated. A spring system, which connects the missile to a rotary positioner, guides the read/write element on the data track. In order to achieve an optimum tracking sequence, a second actuator stage is desirable, which compensates for the frequency limitation of the rotary positioner. As part of the EU project PARMA (Performance Advances in Recording through Micro Actuation), a low-cost read/write head with integrated micro actuator (SLIM) was developed to increase the performance of hard disks, which allows both altitude adjustment and high-precision tracking. The dimensions correspond to the conventional "pico" format (1,240 µm x 990 µm x 300 µm). The system is built on two separate wafers. The upper wafer contains the micromechanical part of the system. It contains a mounting beam serving as a runner, which is suspended from two leaf springs and carries a chiplet. The read/write element is located on the chip. The lower wafer carries the micromagnetics in the form of two stators that generate an electromagnetic field. When both stators are excited evenly, the chip is lowered, which is equivalent to an altitude setting. An uneven excitation causes a rotation, whereby a high-precision tracking sequence is achieved. Partners in this EU project are the Microsensor & Actuator Technology Center (MAT) of the Technical University Berlin, the INESC Microsistemas e Nanotecnologias in Lisbon, Portugal, and the Engineering Department of the University of Cambridge in Great Britain.