Enlarged Magnetic Substrate Flatness and Transducer Stability
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Solution Overview
Problem
The challenge in magnetic recording media is achieving substrate flatness while maintaining stable data transducer flight characteristics, as existing polishing processes often result in relief zones that cause instability and performance issues at the outermost active area of the disc, where data transfer rates are highest.
Innovation Solution
The use of enlarged substrates with outer diameters of nominally 97 mm for 3½ inch form factor and 67 mm for 2½ inch form factor HDDs, allowing for a larger radial distance and derating factors to optimize data storage area usage, thereby improving manufacturing yields and performance by reducing sensitivity to elevational changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional polishing processes are used to achieve substrate flatness, then the substrate surface is flattened, but relief zones are created at the outermost active area causing transducer flight instability
Solution Approach 1:
The patent applies different surface characteristics to different regions of the substrate. The inner and middle regions maintain high flatness for stable transducer flight, while the outermost region intentionally allows relief zones to exist. This local differentiation resolves the contradiction by permitting relief zones only where they do not interfere with active data recording areas, thus maintaining transducer stability while achieving substrate flatness where needed.
2Area of moving object
If the substrate outer diameter is increased to increase recording area, then more data storage capacity is available, but sensitivity to elevational changes increases at the outermost radius
Solution Approach 1:
The patent implements local quality by creating distinct zones across the substrate radius. The inner and middle zones are polished to high flatness specifications to minimize elevational variations, while the outermost zone intentionally permits relief zones. This approach allows the substrate to accommodate larger diameters for increased recording area while maintaining elevational control in the critical data recording regions.
Solution Approach 2:
The patent applies partial polishing action by selectively polishing only the inner and middle regions of the substrate to high flatness, while leaving the outermost region with intentional relief zones. This partial action resolves the contradiction by providing elevational control where recording occurs while accepting imperfections in the outermost region that do not compromise data integrity.
3Productivity
If the outermost diameter is reduced to improve manufacturing yield, then fewer substrates are rejected, but the valuable recording area at high data transfer rates is lost
Solution Approach 1:
The patent uses local quality to maximize substrate utilization by creating a zoned surface where the inner and middle regions have high flatness suitable for recording, while the outermost region contains relief zones. This allows the full substrate diameter to be used, increasing recording area without compromising manufacturing yield, as the relief zones are positioned in non-critical areas.
Data Source
AI summary
Apparatus and method for magnetic recording media. A rotatable magnetic recording disc has an outermost annular sidewall that extends at nominally 97 millimeters, mm for a 3-½ inch form factor data storage device or at nominally 67 mm for a 2-½ inch form factor data storage device. The rotatable magnetic recording disc further has a disc shaped substrate of metal or glass, and a magnetic recording layer supported by the disc shaped substrate and configured to magnetically record data along concentric tracks.