The effect of contamination particles on the dynamics of ultra-low flying air bearing sliders

For complex air bearing slider designs the two dimensional approximation incorporated in the Reynolds equation for determining the airflow in the air bearing is not applicable due to steps in the air bearing surface. A model that incorporates some transverse flow effects is needed to better characterize the airflow between the slider and disk. Such a model is derived here to better predict the paths of contamination particles entrained in the air bearing. The characteristics of airflow and particle flow within the air bearing are then studied. The analysis with transverse effects included reveals that the transverse air velocity is not negligible in the geometric transition regions of the slider. Furthermore, this transverse velocity has a significant effect on the flight path of particles, and therefore, on the particle contamination profile on slider surfaces.; For a particle flying into contact with the slider or disk surfaces, criteria are needed to determine if it sticks or bounces. For an adhesive elastic particle such criteria based on its adhesive energy with the surface are derived and applied. The criteria reveal that nanometer particles are likely to stick to and contaminate the slider and disk surfaces.; For future high areal density hard disk drives, the magnetic spacing is expected to be less than 5nm, and the mechanical clearance between the head and disk is about 3.5nm. For such spacing, the effects of a particle in the head disk interface include the slider's flying height modulation and its MR read-back signal variation. The effects become more severe for less head disk clearance. The modeling of a particle in the head disk interface include three-body contact, frictional heating, and heat conduction due to the frictional heating and cooling effect of the slider air bearing. The contact force exerted on the slider by a nanometer size particle is on the order of 1/1000 gram. The effective force acting on the slider by a large number of particles is comparable to the gram load applied by the suspension in a hard disk drive. It modulates the slider's flying characteristics and changes the head signal sensitivity due to the spacing modulation between the MR sensor and disk media.