Air bearing design considerations for constant fly height applications

Various air bearing designs are compared for a typical 3.5-inch disk drive application. The air bearing designs discussed here are machined taper flat (MTF), shaped rail positive pressure, negative pressure, and transverse pressure contour (TPC). The comparisons are based on the results of computer simulations. The strengths and weaknesses of these designs with respect to some of the important design considerations are discussed. The MTF designs are not capable of constant fly height. The shaped rail positive pressure designs, both two-rail and tri-rail, have significantly flatter fly height profiles, tighter fly height tolerances and better performance as compared to the MTF designs. The TPC designs give near constant by height under a wide range of conditions but are very sensitive to manufacturing tolerances and require tighter process controls than other designs do. They also have large skew sensitivity which results in accessing fly height loss no better than that for shaped rail designs. The negative pressure designs have the best overall performance. They permit low gram load for improved head/disk interface reliability and also work well at high gram loads. The negative pressure designs have tighter fly height tolerances, lower crown sensitivity, lower skew sensitivity, and better accessing performance as compared to the other designs discussed here