Studies of fly stiction

Abstract

A study of fly stiction caused after a head slider flew over a disk surface was conducted to understand the mechanisms responsible for high stiction. In this paper, laser-textured disks and three types of nanosliders (50 per cent of the standard size) were used. Friction/stiction was measured and the r. m.s. acoustic emission was recorded in both a short sweep test where the slider swept for periods of 1 h and a long-sweep test where the slider swept for periods of 6 days. The surface of the head slider after tests was analysed using optical microscopy, atomic force microscopy/frictional force microscopy and Raman spectroscopy. Results showed that, in the short sweep test, stiction was sensitive to environmental humidity. Stiction was low at low humidities and increased with increase in the humidity. In the long-sweep test, liquid droplets accumulated during flying were observed on the head slider surface. The vortex around the head slider was found to be responsible for the accumulation of liquid droplets. The droplets then migrated to the rail surface and led to fly stiction during the following start-up. Stiction was sensitive to these liquid droplets in addition to the humidity. Both negative and positive-pressure sliders could cause fly stiction. A lower flying height was found to be more susceptible to fly stiction. A disk with a fully bonded lubricant film lowered the stiction. Increasing the disk speed could increase the stiction of a negative-pressure slider whereas it lowered the stiction of a positive-pressure slider because of the effects of flying heights, lubricant spin-off and intensity of the vortex