Glass Substrate Cleaning with Oxalate-Iron Solution
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Solution Overview
Problem
The manufacturing process of magnetic disk glass substrates faces challenges in effectively removing metal contaminants, particularly from stainless steel sources, which adhere to the surface and cause unevenness, degrading electric characteristics and reducing yield, especially with the advancement of recording density and Dynamic Flying Height technology requiring smoother surfaces.
Innovation Solution
A method involving a cleaning liquid with oxalate ions and bivalent iron ions under acidic conditions, where the cleaning liquid is reduced using light irradiation or a reducing agent like ascorbic acid, effectively removing metal contaminants while maintaining surface smoothness, using a polishing apparatus with an iron-containing surface plate to dissolve iron-based foreign matters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional cleaning liquid is used to remove metal contaminants, then the cleaning effect is achieved, but the surface roughness of the glass substrate increases
Solution Approach 1:
The patent changes the chemical parameters of the cleaning liquid by introducing a specific composition containing oxalic acid, hydrogen peroxide, and a reducing agent. This parameter change enables the cleaning liquid to effectively remove metal contaminants while maintaining surface flatness, resolving the contradiction between cleaning effectiveness and surface quality preservation.
Solution Approach 2:
The patent uses a reducing agent as an intermediary substance that facilitates the removal of metal contaminants through chemical reduction. This intermediary mechanism allows for effective cleaning without directly attacking the glass substrate, thereby preventing surface roughening while achieving thorough contaminant removal.
2Productivity
If the cleaning liquid is used continuously, then productivity is improved, but the cleaning liquid deteriorates due to oxidation
Solution Approach 1:
The patent incorporates a reducing agent that acts as a feedback mechanism to regenerate oxidized components in the cleaning liquid. As the cleaning liquid undergoes oxidation during continuous use, the reducing agent counteracts this deterioration, maintaining the cleaning effectiveness and enabling sustained productivity without frequent liquid replacement.
Solution Approach 2:
The patent formulates the cleaning liquid with components that maintain their effectiveness over time through continuous regeneration. The reducing agent continuously restores oxidized substances, ensuring the cleaning liquid remains active and effective throughout extended operation, thereby achieving continuous cleaning capability without loss of performance.
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
This method effectively removes metal contaminants without increasing the surface roughness of the glass substrate, ensuring high recording density and smoothness necessary for advanced magnetic disk technologies, such as DFH heads, by regenerating the cleaning liquid through photoreduction and stabilizing the pH.
Implementation Method 1
a cleaning step of cleaning the glass substrate after the polishing step, wherein: in the cleaning step, the cleaning is performed under an acidic condition using a cleaning liquid containing oxalate ions and bivalent iron ions
Implementation Method 2
the cleaning step including an operation of reducing the cleaning liquid
Implementation Method 3
using a polishing apparatus with an iron-containing surface plate to dissolve iron-based foreign matters
Data Source
AI summary
A method of manufacturing a magnetic disk glass substrate has a cleaning step of cleaning the glass substrate. In the cleaning step, the cleaning is performed under an acidic condition using a cleaning liquid containing oxalate ions and bivalent iron ions. In parallel with the cleaning step or before or after the cleaning step, trivalent iron ions generated by oxidation of the bivalent iron ions contained in the cleaning liquid are reduced by ultraviolet irradiation.