Slider Air-Bearing for Lower Fly Height, Improved Durability, and Reduced Repeatable Run-Out
Original Publication Date: 2001-Aug-01
Included in the Prior Art Database: 2003-Jun-18
Described is a modified slider air bearing surface (ABS) that has small features produced on the ABS to keep the majority of the area of the slider away from the disk during intermittent slider-disk interactions (SDIs) at low fly heights. As a result, the frictional or drag forces developed between the slider and the disk are minimized during contact events. This results in a more durable slider-disk interface, and also reduced lateral repeatable run-out (RRO) of the slider originating from such forces. Although the same results might be achieved by controlling features on (i) the disk or (ii) slider or (iii) both, there are significant advantages in modifying the slider alone as embodied in this invention. Since the area of a slider is much less than the area of a whole disk, and the area occupied by said small features on the slider ABS is much less than the entire slider area, the manufacture of these small slider features can be more easily accomplished than modifying an entire disk to achieve the same end. Furthermore, when one considers slider fabrication methods, it is apparent that producing small slider features is a more manufacturable process than standard processes directed towards controlling the roughness of the entire slider ABS surface through controlled lapping. Historically, the basis for this invention was laid through experiments on the flyability of disks. It was found that disks rougher on an AFM-length scale (wavelengths ~1-10 um and less), such as measured by Rq (root-mean-square roughness) and other AFM parameters, produced lower RRO in file tests. The onset of the increased SDIs for a rougher disk occurred at lower fly heights. In addition, file testing has corroborated that lower RRO occurs for rougher disks at lowest fly heights. A plausible explanation for this effect is that disk roughness lowers RRO by reducing the contact area between the slider and the disk. This becomes apparent when one considers the limiting case of the contact of the tallest asperities of a rough surface with a smoother surface of greater contact area. Also, it was found that the areal density of tall asperities can, under certain disk substrate manufacturing conditions, be minimized as roughness is increased. While testing continued on "rougher" disks, it was recognized and understood by the inventors for some time that modifications can also be made to the slider that might achieve the same results observed with rough disks. Specifically, the contact area of the slider could be minimized in some way, as opposed to roughening the disk substrate to produce tall, isolated asperities. To test the plausibility of this idea, a completed slider was milled using a focused ion beam (FIB) tool. The trailing edge of the ABS was cut to a depth of ~250um, and most of the rear ABS pad was removed except for some narrow outriggers at its edges. The results of tests performed on FIBed heads showed reduced RRO rivalling that of a rough disk. Similar results were found for sliders with pads on the ABS used to stand-off the slider from the disk. The results of the experiments with modified slider ABSs clearly demonstrated the utility of this invention as a means for improving slider-disk durability and reducing RRO.