Pre-patterned Discrete Track Media for Self-Servowriting
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Solution Overview
Problem
Existing methods for writing servo patterns on magnetic disks face challenges in accommodating eccentricity and non-circularity of pre-patterned discrete tracks, leading to inefficiencies in planarization and increased servo overhead, which hinders the achievement of higher areal densities in magnetic disk drives.
Innovation Solution
The development of pre-patterned discrete track media that allows for self-servowriting with Integrated Servo patterns, which includes land and groove patterns for two or more Integrated Servo sequence fields per servo sector, enabling adaptation to eccentricity and non-circularity, and a bootstrap zone with pre-patterned features for initial servo pattern detection and compensation, facilitating self-propagating servo writing across the disk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional servowriting methods are used with pre-patterned discrete tracks, then servo patterns can be written on the disk, but the method requires stringent control over head position and increases device complexity
Solution Approach 1:
The disk drive's own read/write heads perform the servowriting operation, eliminating the need for a separate dedicated servowriter device. The system uses its existing heads to write servo patterns to the pre-patterned discrete tracks, thereby simplifying the overall device architecture while maintaining manufacturing precision through self-service capability
Solution Approach 2:
The read/write heads are designed to perform multiple functions: they can both read/write data and write servo patterns. This multi-functionality eliminates the need for separate dedicated servowriting heads or devices, reducing device complexity while maintaining the precision required for servo pattern writing on pre-patterned discrete tracks
2Manufacturing precision
If dedicated servowriter is used to write servo patterns, then precise servo information can be written, but the manufacturing process becomes more complex and time-consuming
Solution Approach 1:
The servowriting process is merged with the existing disk drive manufacturing process. Instead of using a separate dedicated servowriter in a clean room environment, the disk drive's own heads perform the servowriting, combining multiple operations into a single integrated process that simplifies manufacturing while maintaining precision
Solution Approach 2:
Pre-patterned features are created during the disk manufacturing process before the disk is installed in the drive. These pre-patterned discrete tracks serve as guides for the subsequent self-servowriting operation, allowing the servo patterns to be written with high precision without requiring complex real-time positioning systems
3Reliability
If servo overhead is increased to accommodate eccentricity compensation, then track following improves, but areal density decreases
Solution Approach 1:
Different regions of the disk have different servo pattern characteristics. The pre-patterned discrete tracks and servo patterns are designed with local variations to accommodate eccentricity and non-circularity in specific areas, allowing accurate track following without requiring uniform increases in servo overhead across the entire disk surface
Solution Approach 2:
The servo control system dynamically adjusts to eccentricity and non-circularity variations during disk rotation. By using feedback from the servo patterns written on pre-patterned discrete tracks, the system can compensate for rotational variations in real-time, maintaining track following accuracy without requiring excessive servo overhead that would reduce areal density
Data Source
AI summary
Pre-patterned discrete track media for self-servo writing are described. Embodiments include land and groove patterns for two or more Integrated Servo sequence fields for each servo sector in which one of the Integrated Servo sequence fields is aligned with the data track and a second sequence is offset by one-half of a track width. The lands and grooves between the Integrated Servo sequence fields are preferably the same width as those between the data tracks to facilitate planarization. Alternative embodiments include a sync feature for each servo sector formed by a selected groove and/or land pattern as a marker for the start of the servo fields. Alternative embodiments include a bootstrap zone with servo patterns that are readable when DC-magnetized. Described methods of self-servowriting include ways to adapt to eccentricity and non-circularity of pre-patterned discrete tracks with respect to the head paths.