Critical Operating Conditions For A Novel Flying Tester

Increased recording densities are often achieved through a reduction in the flying height over a thin film disk possessing diminishing surface roughness. Flying heights will continue to decrease until the head-disk interface (HDI) operates under quasi-contact conditions, i.e., ultra-low flying with intermittent slider-disk collisions. The failure mechanisms that occur in such quasi-contact devices may differ from those experienced in current, higher flying hard drive assemblies. In this paper, the authors will present the experimental, numerical, and theoretical tools that have been developed to study the behavior of the HDI under ultra-low flying conditions. These tools include an accelerated flyability tester and a numerical algorithm applicable to highly rarefied air bearings that possess large pressure gradients. Air bearing simulation results, as well as the results from a simple flying height scaling analysis, will be compared to flying test results in both air and helium to obtain insight into the stability of the HDI under accelerated testing conditions. A new concept introduced in this paper is that of critical conditions, i.e., the band of operating conditions which mark the transition from stable to erratic behavior, which can be determined both experimentally and theoretically. Such insight should provide design criteria for both quasi-contact storage devices, as well as novel accelerated wear testers.