2005 Volume 20 Issue 2 Pages 153-159
An increase in storage capacity of hard disk drives (HDDs) resulted in a reduction in flying height (clearance between hard disk (HD) and magnetic head) to be in the order of nanometer. The small flying height made the HDs more sensitive to the surface contamination, which very often led to fatal failures. The present work studied the HD surface contamination with SO2 by exposing lubricant-coated HDs to cleanroom (CR) air as well as to SO2-containing test air. As a result, the adsorption of SO2 in CR air was expressed by an adsorption kinetic equation based on Langmuir isotherm, while the equation was not applicable to the adsorption of SO2 in test air. The sticking probability of SO2 in test air onto the lubricated HD was found to be about one tenth of that for SO2 in CR. The difference may be attributed to the enhanced adsorption of SO2 by basic gases present in CR. This result suggests that SO2 adsorption onto HD surface should be evaluated by the exposure to CR air and that the data obtained by the exposure to model gas might be misleading. For the suppression of HD surface contamination by SO2, it is necessary to equip CR with an integrated air purification system for basic gases and SO2.
