Magnetic Recording Substrate Edge Region Assessment
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Solution Overview
Problem
Existing methods for identifying substrates suitable for magnetic recording media in data storage devices often focus on overall flatness, neglecting height variations and irregularities in the outer diameter edge regions, which can affect the reliability of data reading.
Innovation Solution
A method that determines roll-off, ski-jump, and radial-waviness values in the outer diameter edge region of a substrate, calculates the minimum fly height between a slider and the substrate based on these values, and compares it to a fly height threshold to determine substrate suitability for magnetic recording media.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If only overall flatness is measured for substrate identification, then the measurement process is simple, but the reliability of data reading is compromised due to unaccounted height variations in OD edge regions
Solution Approach 1:
The substrate surface is divided into multiple measurement zones: the outer diameter edge region (within 2mm of the edge) and the inner region. Different measurement parameters are applied to each zone - roll-off, ski-jump, and radial-waviness values are specifically measured in the OD edge region, while overall flatness is measured across the entire surface. This segmentation allows comprehensive assessment of critical areas without unnecessarily complicating the measurement of less critical areas.
Solution Approach 2:
The patent applies different measurement criteria to different regions of the substrate. The OD edge region requires specific local measurements (roll-off, ski-jump, radial-waviness) because height variations here directly impact slider contact and data reading reliability. The inner region is assessed using overall flatness measurements. This local quality approach ensures that measurement complexity is applied only where it provides value for reliability.
2Productivity
If substrates with height variations in OD edge region are used, then substrate utilization increases, but the risk of slider contact and data reading failure increases
Solution Approach 1:
The patent performs preliminary measurement and evaluation of the substrate's OD edge region characteristics (roll-off, ski-jump, radial-waviness values) before the substrate is used in the magnetic recording device. The minimum fly height is calculated in advance based on these measurements. This preliminary action allows substrates to be screened and approved before use, ensuring that even substrates with some height variations meet the minimum fly height requirement, thus maintaining reliability while maximizing utilization.
Solution Approach 2:
The patent establishes a feedback mechanism where the measured height variations in the OD edge region are used to calculate the minimum fly height, which is then compared against a threshold requirement. This feedback loop provides quantitative criteria for substrate acceptance or rejection, allowing systematic decision-making that balances substrate utilization with data reading reliability. Substrates that meet the calculated minimum fly height threshold are approved for use, ensuring reliability is maintained.
3Measurement precision
If comprehensive surface characteristics including roll-off, ski-jump, and radial-waviness are measured, then substrate suitability assessment accuracy improves, but measurement time and complexity increase
Solution Approach 1:
The measurement process is segmented into focused measurements of specific critical parameters (roll-off, ski-jump, radial-waviness) in the critical OD edge region, rather than attempting to measure all possible surface characteristics across the entire substrate. This segmentation achieves high assessment accuracy for the parameters that most impact reliability while limiting measurement time by concentrating efforts on the most critical areas.
Solution Approach 2:
The patent measures specific critical parameters (roll-off, ski-jump, radial-waviness) in the OD edge region with high precision, rather than attempting exhaustive measurement of all surface characteristics. This partial action approach focuses measurement resources on the parameters that have the greatest impact on slider contact and data reading reliability, achieving sufficient assessment accuracy without the time cost of comprehensive exhaustive measurement.
Data Source
AI summary
Methods and apparatus of identifying a substrate suitable for a magnetic medium of a data storage device configured for magnetic recording are described. In an aspect, the method includes determining a roll-off value, a ski-jump value, and a radial-waviness value, each associated with an outer diameter (OD) edge region of a data surface of the substrate, and determining a calculated minimum fly height between a slider of the data storage device and a data surface of the substrate in the OD edge region based on the roll-off value, the ski-jump value, and the radial-waviness value. The method further includes comparing the calculated minimum fly height and a fly height threshold, and determining whether to utilize the substrate for the magnetic medium based on the comparison of the calculated minimum fly height and the fly height threshold.