Architecture and performance of the ESPER-2 hard-disk drive servo writer

  • Authors:

  • H. Ono

  • Affiliations:

  • IBM Japan Display Technology Laboratory, Yamato-shi, Kanagawa-ken, Japan

  • Venue:
  • IBM Journal of Research and Development
  • Year:
  • 1993

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Abstract

The servo writer is known as the most accurate and sensitive tool on an HDD (harddisk drive) manufacturing line. ESPER-2 is designed as a product-independent common servo writer which incorporates major advances in equipment cost, reduction of clean-room requirements, and writing accuracy. The servo writing process consists of two stages. The first stage writes the master servo pattern on as many as ten disks at once with little need for contaminant protection facilities. One such master disk is then assembled with other, raw, disks in a file, and the second stage writes the proper servo pattern on all disk surfaces by referring to the master. The effects of off-center discursions in the mechanical disk assembly and random runout (NRRO, or nonrepeatable runout) in the product spindle components are eliminated by table-lookup servo actuator control, so that writing accuracy is improved. Neither an exceptionally clean environment nor fine mechanical parts are required for the second-stage operation.