Polishing Composition for Magnetic Disk Substrates
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Solution Overview
Problem
Conventional polishing compositions for aluminum magnetic disk substrates with electroless nickel-phosphorus plating face issues with embedded alumina particles affecting subsequent polishing steps and the combination of alumina and silica particles leading to negated properties, resulting in suboptimal polishing rates and surface smoothness.
Innovation Solution
A polishing composition combining colloidal silica with specific particle sizes (5-200 nm) and wet-process silica particles (0.1-1.0 μm) in a particular ratio, along with an acid and oxidizing agent, to achieve a high polishing rate and surface smoothness without using alumina particles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If alumina particles with relatively large particle sizes are used in polishing composition, then polishing rate is improved, but alumina particles are embedded in the substrate causing adverse effects on subsequent polishing steps
Solution Approach 1:
The patent removes alumina particles from the polishing composition entirely, extracting the harmful component while retaining silica particles as the sole abrasive. This eliminates the embedding problem while maintaining polishing effectiveness through optimized silica particle characteristics and combination ratios.
Solution Approach 2:
The patent changes the particle size parameters of silica particles to specific ranges (0.01-1.0 μm for first silica, 0.1-10.0 μm for second silica) and optimizes their combination ratio. This parameter optimization achieves high polishing rate without embedding, resolving the contradiction between productivity and reliability.
2Reliability
If alumina particles and silica particles are combined in polishing composition, then embedded alumina particles are removed to some degree, but the respective properties of alumina and silica particles are negated with each other, leading to worsening of polishing rate and surface smoothness
Solution Approach 1:
The patent extracts alumina particles from the polishing composition, using only silica particles. This eliminates the mutual negation of properties between different particle types while maintaining the ability to remove embedded particles through optimized silica particle characteristics.
Solution Approach 2:
The patent creates a composite polishing system using two types of silica particles with different size ranges working synergistically. The first silica (0.01-1.0 μm) provides fine polishing and the second silica (0.1-10.0 μm) provides cutting action, achieving both high polishing rate and good surface smoothness without the drawbacks of alumina-silica combinations.
3Reliability
If polishing is performed using only silica particles, then embedded alumina particles are not removed, but sufficient polishing rate and surface smoothness can be achieved
Solution Approach 1:
The patent employs a composite system of two silica particle types with complementary size ranges. The smaller first silica particles (0.01-1.0 μm) ensure surface smoothness while the larger second silica particles (0.1-10.0 μm) provide enhanced cutting ability and polishing rate, achieving both reliability and productivity improvements over single-type silica.
Solution Approach 2:
The patent optimizes the particle size parameters and combination ratio of silica particles to achieve both high polishing rate and good surface smoothness. By carefully controlling the size distribution and proportion of different silica particles, the system overcomes the limitations of using silica alone while avoiding the problems of alumina-containing compositions.
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 composition significantly enhances polishing rate and surface smoothness, exceeding expectations when used alone, with a synergistic effect between the silica types, improving both polishing performance and surface characteristics.
Implementation Method 1
polishing composition including colloidal silica and pulverized wet-process silica particles
Implementation Method 2
polishing composition including colloidal silica and pulverized wet-process silica particles, wherein a value of the ratio
Data Source
AI summary
Embodiments of the invention provide a polishing composition including colloidal silica having an average particle size of 5 to 200 nm and pulverized wet-process silica particles having an average particle size of 0.1 to 1.0 μm, wherein a value of the ratio of the average particle size of the wet-process silica particles to that of the colloidal silica is from 2.0 to 30.0. The polishing composition, according to various embodiments, achieves a high polishing rate and has a good surface smoothness, without the use of alumina particles.