Browse Prior Art Database

Disk Storage Device with Calibrated Media Asperities Disclosure Number: IPCOM000014585D
Original Publication Date: 2000-Jun-01
Included in the Prior Art Database: 2003-Jun-19

Publishing Venue



A disk storage device may have one or more isolated asperities of defined height and shape which may be on each disk surface in a regular or irregular pattern preferentially away from the data zone, and separated by a distance substantially greater than a slider length. These asperties, which may be made by disk substrate modification or a deposited structure on the disk, would be used for automated glide test transducer calibration or comparison of asperities on the disk surface, may be used in disk manufacturing. In a typical application, the asperitiy height may be, but not limited to, about twice the flying height of the glide transducer air bearing slider. Asperities on disks and can be a large source of yield loss in disk and HDD manufacturing, signficantly impacting manuacturing yield and field reliability. Calibrating the transducer which determines height and distribution of asperities on a disk is currently very difficult, and requires a time consuming process in manufacturing. Events which may degrade the flying characteristics or sensitivity of the glide transducer can go unnoticed without frequent recalibration. This is a time consuming process, and as a result, there exists significant risk for variation in single disk glide test sensitivity, leading to escapes of disk defects to the HDD manufacturing and field. When a "glide head" encounters an asperity it generates an electrical signal. Uncertainties in the calibration of this signal to the height of the asperity is large. There are many reasons for this, some of which may be multiple transfers of the calibration standard to the tester, changes in the fly-height of the glide head due to debris accumulation, disk curvature, etc. These uncertainties cause large variations in glide yields between testers. Even with glass disks, yield variations of 15% between different testers is not unusual. Using the bumps manufactured onto the disk, the tester calibration could be verified frequently, perhaps self-calibrated with each disk. This would reduce the variations between testers and greatly increase the precision. It would also reduce the number of escapes from the glide test, leading to potential yield improvements. Furthermore, the escape rate and precision of the glide test would be improved by this invention and the glide specifications could be loosened, increasing yield. Uses of these bumps are not limited to Disk Manufacturing. They could be used in the disk drive product to help assess the size of thermal asperities. If these bumps were judiciously placed, for instance at the inner diameter of the disk, little "real estate" that could be used for data storage would be compromised. Furthermore, since the location of these bumps could be known, the area around the bumps could be padded so that the bumps themselves do not cause thermal asperities. The laser tools used to make the bumps currently used in calibrating glide testers could be adjusted for production use. Laser texture tools that are now used to make bumps for the landing zone on a metal disk, could be adjusted to put fewer bumps on the disk. 1