Symmetric Servo Patterns for Planarized Magnetic Disks
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Solution Overview
Problem
Existing servo pattern writing techniques for patterned magnetic disks face challenges in complying with planarization constraints and efficiently using a single master template for both sides of the disk, particularly due to varying sizes and shapes of gray code track-ID and sector-ID formats, and the need for mirror symmetric patterns to accommodate reverse reading directions.
Innovation Solution
The implementation of robust servo patterns that are symmetrically designed with two servo write assist patterns on each side of a central burst pattern, allowing for both left-to-right and right-to-left writing and reading, while adhering to planarization constraints, enabling the use of a single master template for manufacturing both sides of the magnetic disk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single master template is used for manufacturing both sides of the magnetic disk, then manufacturing efficiency is improved, but the servo pattern design becomes more complex due to mirror symmetry requirements
Solution Approach 1:
The patent applies asymmetry by creating mirror-symmetric servo patterns where the left and right sides of the servo sector are designed as mirror images of each other. This allows a single master template to be used for both sides of the disk, as the template can be flipped to create the appropriate pattern for each side. The servo write assist patterns are positioned symmetrically around the central burst pattern, enabling bidirectional reading and writing operations from one template.
2Ease of manufacture
If servo patterns are designed to comply with planarization constraints, then manufacturing feasibility is improved, but the flexibility in pattern design is reduced
Solution Approach 1:
The patent applies local quality by designing the servo pattern with different regions having specific properties tailored to planarization constraints. The servo write assist patterns are positioned at specific locations with controlled dimensions and spacing that satisfy planarization requirements. The central burst pattern and servo data regions are locally optimized to meet manufacturing constraints while maintaining functional requirements for servo operations.
Data Source
AI summary
Embodiments described herein provide for robust servo patterns that comply with planarization constraints and also allow use of a single master template for manufacture of both the front and back of a magnetic disk. Planarization constraints are met because only a portion of servo data is hard patterned on the magnetic disk and the hard patterned servo data areas comply with planarization constraints. The servo pattern has two symmetrical servo write assist patterns, one on each side of a central burst pattern. The servo sync, SAM, track-ID, sector-ID, and/or RRO values can be written magnetically by the write head onto these servo write assist patterns after the completion of the planarization process. The symmetric design of the servo pattern allows both a left-to-right and a right-to-left servo write and read back, thereby enabling use of a single master template in magnetic disk manufacture.