WTC2005-63320 EFFECTS OF PITCH STATIC ATTITUDE AND ROLL STATIC ATTITUDE ON THE STEADY PERFORMANCE OF AIR BEARING SLIDERS

ABSTRACT This paper addresses the effects of pitch static attitude (PSA) and roll static attitude (RSA) on air bearing slider steady performance, especially for ultra-low flying height sliders. We performed simulations for three different low flying sliders with flying heights (FH) of 7nm, 5nm and 3.5nm using the static simulator code of the Computer Mechanics Laboratory (CML). We found that PSA and RSA have quite significant effects on the steady performance of these air bearing slider designs, and the effect is more important the smaller the size and the lower the FH of the slider. We also investigated the effects of suspension stiffness on the air bearing sliders' flying attitude (pitch and roll) and found that these effects are similar to those of PSA and RSA. INTRODUCTION When air bearing sliders for use in hard disk drives (HDD) are mounted onto the flexure or gimbal of the suspension an initial pitch angle and roll angle are formed, by design or inadvertently. These are called the Pitch Static Attitude (PSA) and Roll Static Attitude (RSA). These two angles can greatly affect the magnitude of the pitch and roll torque applied to the slider when it is forced to align with the disk. In this study, we investigate the effects on PSA and RSA on air bearing sliders' flying attitudes. And we also explore the effects of pitch and roll stiffness on slider steady performance. In a recent program of the Information Storage Industry Consortium (INSIC) several ultra-low flying air bearing sliders were designed, built, and tested. It was found that the sliders of the same design had a distribution of flying attitudes. Much of this difference was eventually attributed to possible differences in PSA and RSA of the slider-suspension assemblies

Three-Dimensional Direct Simulation Monte Carlo Method for Slider Air Bearings

The direct simulation Monte Carlo (DSMC) method is used to solve the three-dimensional nano-scale gas film lubrication problem between a gas bearing slider and a rotating disk, and this solution is compared to the numerical solution of the compressible Reynolds equations with the slip flow correction based on the linearized Boltzmann equation as presented by Fukui and Kaneko [molecular gas film lubrication (MGL) method] [ASME J. Tribol. 110, 253 (1988)]. In the DSMC method, hundreds of thousands of simulated particles are used and their three velocity components and three spatial coordinates are calculated and recorded by using a hard-sphere collision model. Two-dimensional pressure profiles are obtained across the film thickness direction. The results obtained from the two methods agree well with each other for Knudsen numbers as large as 35 which corresponds to a minimum spacing of 2 nm. The result for contact slider is also obtained by the DSMC simulation and presented in this paper

Parametric Investigations at the Head-Disk Interface of Thermal Fly-Height Control Sliders in Contact

Accurate touchdown power detection is a prerequisite for read-write head-to-disk spacing calibration and control in current hard disk drives, which use the thermal fly-height control slider technology. The slider air bearing surface and head gimbal assembly design have a significant influence on the touchdown behavior, and this paper reports experimental findings to help understand the touchdown process. The dominant modes/frequencies of excitation at touchdown can be significantly different leading to very different touchdown signatures. The pressure under the slider at touchdown and hence the thermal fly-height control efficiency as well as the propensity for lubricant pickup show correlation with touchdown behavior which may be used as metrics for designing sliders with good touchdown behavior. Experiments are devised to measure friction at the head-disk interface of a thermal fly-height control slider actuated into contact. Parametric investigations on the effect of disk roughness, disk lubricant parameters, and air bearing surface design on the friction at the head-disk interface and slider burnishing/wear are conducted and reported

Effects of Altitude on Thermal Flying-Height Control Actuation

Thermal flying-height control (TFC) is now a key technology used in hard-disk drives (HDD) as an effective way to push the magnetic spacing to sub-5 nm. Precise control of the TFC sliders’ actuated flying-height (FH) is a major consideration in improving the read/write capability as well as reducing the reliability problem. In this paper, we investigate the response of TFC sliders to altitude changes with a focus on the variation of actuated FH. Numerical and experimental results both indicate an increase in the actuated FH at higher altitudes. Simulations show that the increased TFC protrusion and less air bearing pushback on sliders at higher altitudes contribute to this increase. This study is of practical importance for improving heater and air bearing surface design to reduce the TFC sliders’ sensitivities to altitude changes