Glass Sheet Microwaviness Control for Magnetic Disk Substrates
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Solution Overview
Problem
Magnetic recording disks require glass substrates with smooth and defect-free surfaces, but existing glass sheets often necessitate costly polishing and lapping processes to achieve the necessary surface quality, increasing production costs and efforts.
Innovation Solution
A glass sheet is provided with a controlled surface condition, where the root mean square of surface topography (microwaviness) is between 1.2 nm and 2.8 nm, measured using a laser Doppler vibrometer, to minimize subsequent processing steps and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional glass sheets are used for magnetic recording disk substrates, then the glass substrates can be produced, but costly polishing and lapping processes are required to achieve the necessary surface quality
Solution Approach 1:
The glass sheet is pre-formed with a controlled micrawaviness surface condition (RMS between 1.2 nm and 2.8 nm) before being cut into substrates. This preliminary surface control eliminates the need for subsequent polishing and lapping operations, directly resolving the contradiction between manufacturing precision and ease of manufacture
Solution Approach 2:
The invention changes the surface topology parameter of the glass sheet by controlling the micrawaviness RMS to a specific range (1.2 nm to 2.8 nm). This parameter optimization allows the glass sheet to serve as a ready-to-use substrate without requiring additional surface finishing processes
2Manufacturing precision
If conventional glass sheets are used for magnetic recording disk substrates, then the glass substrates can be produced, but extensive polishing and lapping processes are required, increasing production efforts
Solution Approach 1:
The glass sheet is pre-formed with a controlled micrawaviness surface condition (RMS between 1.2 nm and 2.8 nm) before being cut into substrates. This preliminary surface control eliminates the need for subsequent polishing and lapping operations, directly resolving the contradiction between manufacturing precision and ease of manufacture
Solution Approach 2:
The invention extracts and eliminates the polishing and lapping processes from the manufacturing workflow by providing a glass sheet that already possesses the required surface quality. This removal of unnecessary steps directly improves productivity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The controlled surface condition reduces processing costs and efforts by allowing direct fabrication of magnetic recording disks with reduced polishing, maintaining high recording density and quality.
Implementation Method 1
a root mean square of a surface topography of the surface features determined using a surface analysis on the first surface with incident and reflected light
Data Source
AI summary
A glass sheet configured to be cut into glass substrates for magnetic recording disks is described. The glass sheet includes a first surface. For surface features of the first surface with a feature wavelength of 60 to 500 micrometers (μm), a root mean square of a surface topography of the surface features determined using a surface analysis on the first surface with incident and reflected light is given as a microwaviness. A maximum value of the microwaviness of any arbitrary region of the first surface may be between 1.2 nanometers (nm) and 2.8 nm, inclusive of 1.2 nm and 2.8 nm. After the surface analysis, the glass sheet may be cut into the glass substrates in response to determining that the maximum value of the microwaviness is in the noted range. Further, a method of fabricating glass substrates from a glass sheet is described.