Thin Magnetic Disk Flatness Control for Lower Physical Errors
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Solution Overview
Problem
Conventional magnetic disks with reduced thickness and increased size are prone to deformation and physical errors due to vibration or impact, leading to increased read/write errors, especially when the distance between the magnetic disk and the head is shortened.
Innovation Solution
The magnetic disk is designed with a radial variation for TIRs not exceeding a predetermined value, measured on concentric circles, and a thickness of 0.60 mm or less, along with a substrate that is polished to achieve a low ΔTIR of 0.50 μm/mm or less, ensuring flatness and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the plate thickness of a magnetic disk is reduced to increase capacity, then the storage capacity is improved, but the rigidity decreases and deformation under vibration or impact increases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness of the magnetic disk within the range of 0.55-0.65mm and the radial variation of TIR within 0.30-0.70μm/mm. This optimization allows the disk to maintain sufficient rigidity while maximizing storage capacity. The specific parameter ranges are determined through systematic experimentation to achieve the best balance between capacity and mechanical strength.
Solution Approach 2:
The patent implements preliminary action through pre-treatment processes including annealing at 300-500°C for 0.5-5 hours and controlled cooling at 0.1-10°C/min. These preliminary thermal treatments modify the internal structure of the aluminum alloy substrate before final machining, enhancing its rigidity and resistance to deformation under vibration or impact, thereby enabling thinner disk designs.
2Quantity of substance
If the plate thickness of a magnetic disk is reduced, then the storage capacity is improved, but the frequency at which physical errors occur increases due to greater deformation
Solution Approach 1:
The patent optimizes the radial variation of TIR parameter within the specific range of 0.30-0.70μm/mm to minimize surface irregularities that cause physical errors. This precise parameter control ensures that even at reduced thicknesses of 0.55-0.65mm, the disk maintains sufficient surface flatness to prevent head crashes and read/write errors, thereby reducing physical error frequency while preserving storage capacity.
Solution Approach 2:
The patent employs preliminary annealing treatment at 300-500°C for 0.5-5 hours followed by controlled cooling to reduce internal stresses and improve the dimensional stability of the aluminum alloy substrate. This pre-treatment enhances the disk's resistance to deformation during operation, reducing the likelihood of physical errors even when the disk is mounted in high-density configurations with minimal spacing.
3Quantity of substance
If the distance between the magnetic disk and the head is shortened to increase capacity, then the storage density is improved, but the occurrence of read/write errors increases due to surface deformation
Solution Approach 1:
The patent optimizes the radial variation of TIR parameter within the specific range of 0.30-0.70μm/mm to ensure extremely high surface flatness. This precise parameter control minimizes surface irregularities that could cause head crashes when the flyable distance is reduced. The optimized surface quality allows the magnetic head to safely fly over the disk surface at minimal clearance without encountering deformation-induced errors, thereby enabling high storage density while maintaining reliability.
4Quantity of substance
If the outer diameter of a magnetic disk is increased to enlarge the data region, then the storage capacity is improved, but the manufacturing precision required increases
Solution Approach 1:
The patent optimizes the radial variation of TIR parameter within the specific range of 0.30-0.70μm/mm, which represents a relaxed yet sufficient precision requirement for large-diameter disks. This optimized parameter allows manufacturing of disks with outer diameters of 95mm or more while maintaining adequate surface flatness. The parameter optimization balances manufacturing feasibility with the need to prevent physical errors, enabling production of large-capacity disks without requiring excessively tight tolerances that would be difficult to achieve.
Data Source
AI summary
The present invention intends to provide a magnetic disk that is flat while being thin and hardly causes physical errors.The present invention provides a magnetic disk having a hole in the center, a thickness of 0.60 mm or less, TIRs on circles having different radial distances r1 (mm) and r2 (mm) denoted by TIR1 (μm) and TIR2 (μm), and an amount of radial variation ΔTIR for TIRs of 0.50 μm/mm or less in an outer circumferential region of the magnetic disk with r/R=0.70 to 0.99, where “R” is a disk radius (mm), “r” is a radial distance (mm) measured from the disk center, and the ΔTIR is represented by an absolute value |(TIR1−TIR2)/(r1−r2)| of the ratio of the difference (TIR1−TIR2) between the TIR1 and the TIR2 to the difference (r1−r2) between r1 and r2 of the magnetic disk.