High fly-stiction as a result of grease contamination

Fly-stiction is a special kind of stiction that occurs at the interface between a hard drive head and the hard disk. It can have very high values and has caused serious problems for the computer industry in the past. It is defined as that taken after a certain number of CSS cycles in the landing zone of a disk, followed by an extended period of time of sweep or track dwell in the data zone and finally an extended period of park time in the landing zone. This paper has studied the nature, mechanism and solutions of the high fly-stiction phenomenon. CSS testers, optical microscopes, an optical surface analyzer and a Fourier transform infrared spectrometer were used to measure fly-stiction values and analyze the test surfaces of heads and disks. The results obtained indicate that the fly-stiction value is much higher than the corresponding park-stiction value. The fly-stiction value does not change with increasing number of CSS cycles, and may decrease slightly with increasing lubricant thickness. In addition, a high fly-stiction value may be caused by a contamination of spindle grease. Finally, a high fly-stiction value can be reduced by avoiding contamination or increasing the resistance to contamination of a disk. For instance, an ion-beam carbon overcoat can reduce the fly-stiction to half the value obtained with a sputter carbon overcoat.