Flying Height Drop Due to Air Entrapment in Lubricant

Abstract

Recently, it is found experimentally that the flying height of an air bearing slider is influenced by the lubricant on the disk. It is explained as the air molecules are entrapped in the lubricant under the slider due to the high air bearing pressure, causing the reduction in air bearing force, and hence, the flying height decreases accordingly. This paper employs both experiment and simulation to study such a phenomenon. First, the flying height vibration signals of a slider are detected by a laser Doppler vibrometer, on both lubed and delubed disks. It is observed that the heater touchdown power of the slider is approximately 3.4 mW more for delubed disk than the lubed disk. It suggests that the lubricant may cause the flying height lower. Second, a new model is developed to describe the pressure drop due to the air entrapment. Next, simulations are conducted on three different slider designs based on the new model. Flying height drops are investigated due to the air entrapment. The simulation results are compared with published experimental results, and good correlations are observed for the values of the parameters alpha and beta selected. Finally, the effects of solubility on the flying height are discussed, and the flying height drops are evaluated. It is suggested that the slider design must consider the phenomenon to get more accurate simulation results on flying height.