Production process and high density recording characteristics of plated disks

A high density recording plated disk, which consists of a chemically plated Co-Ni-P medium and a spin-coated and lubricated SiO2overcoat, has been developed using techniques based on extensive studies on error defects, wear durability and wet durability throughout all the production processes. The plated disks were evaluated by practical level tests. The average numbers of error defects were about 50 per surface at 620FRPM (15,700FRPI) linear density measured with 18.5 μm track width Mn-Zn ferrite heads. The plated disk wear durability was sufficient for 20,000 contact start/stop (CSS) cycle tests and 10⁸times seek motion test at 0.2 μm flying height with Mn-Zn ferrite heads. Wet durability was determined for humidity tests under 40 °C, 80% R. H. for 7 months. Errors were not increased after the tests. Based on these excellent evaluation results, the plated disks are used in an 8 inch high performance 400 MB disk drive developed by NTT. Further, higher density recording characteristics of the plated disk were investigated using narrower gap length Mn-Zn ferrite heads at smaller head-medium spacings. As a result, 2,900 FRPM (74K FRPI) linear recording density was obtained as D50with a 0.03 μm thick Co-Ni-P medium disk and a 0.2 μm gap length head at 0.12 μm head-medium spacing.