A brief historical review of the head–disk interface evolution is presented, and current limitations when facing stringent tribology requirements for high-density recording are addressed. The tribology performance of sliders with contact landing pads on the air bearing surfaces (the “padded slider”) was studied. Lightly mechanically textured disks, and laser zone-textured disks with shallow bumps (the “light LZT”) to reduce glide avalanche that were specially designed for padded sliders were used. When the smoother mechanically textured surface was applied, we observed inferior constant start-stop (CSS) durability due to possible tribological degradation of the padded slider, and significant landing pad wear was observed on the slider after the CSS test. Rougher surfaces including the light LZT surface, however, were not as sensitive to tribological degradation of the padded slider as the smoother surface, and exhibited better CSS durability as well as less landing pad wear after the test. Hence the optimization effort of padded slider head/disk component design may be reduced if a light texture is applied on the CSS zone. The head–disk interface consisting of a padded slider on a light LZT can better meet the stringent tribology requirements for high density recording needs and therefore it is proposed as an alternative to ramp loading technology in the desktop/server-class disk drives. Hence the better-understood CSS technology is expected to be further extended into future high-performance disk drives.
The dynamic load head-disk contact induced impact stress was studied. A dual channel LDV was used to measure the head-disk relative motion during impact, and an analytical model incorporating the Hertz theory of impact was developed to quantitatively estimate the impact induced contact force and stress based on the LDV-measured results. 70 percent sliders were used in order to compare the results with our previous study. From the estimated maximum contact stresses and the results of our previous study, it was found that when the average maximum stress was 511 MPa, the head-disk interface did not show any damage after 100,000 cycles of repeated head-disk impacts. When the average maximum stress was 880 MPa, however, 100,000 repeated head-disk impacts caused significant wear of the disk’s overcoat even though a single impact did not cause any observable damage. From the analysis it can be seen that a lower head-disk impact velocity and/or a larger radius of curvature at the contacting corner of the slider result in a smaller head-disk impact stress on the disk. Based on the analyses, we estimated the radius of curvature needed for a 50 percent (Nano) slider and a 30 percent (Pico) slider to have at least 100,000 cycles of dynamic load head-disk interface durability. Such radius of curvature can be realized, for example, by edge-blending the sliders. [S0742-4787(00)02901-5]
The effect of head-disk impacts due to repeated dynamic load is investigated experimentally. Loading conditions more severe than those typically found in ramp-load disk drives are applied to ensure that contacts occur, and disk-synchronized head loading motions are applied so that the head-disk contact points are all distributed within a small area on the disk. The resulting readback signal decrease was observed to correlate with the head-disk impact velocity and hence the slider’s vertical approaching velocity. With a larger vertical velocity, readback signal decrease appeared earlier and the amount of decrease was larger. The results indicate that dynamic load-unload should be quite reliable under typical loading conditions, and the reliability of dynamic load-unload can be achieved by controlling the vertical approaching velocity of the slider. This is comparatively easier than controlling the narrow manufacturing tolerances of the slider’s pitch and roll of the head-suspension assembly. The technological trend toward using smaller-sized head-suspension assemblies and higher-coercivity magnetic disks may further enhance the dynamic load head-disk interface durability.
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