Glass Composition for Hard Disk Substrates
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current glass compositions for hard disk substrates face challenges in achieving high Young's modulus, low density, and heat resistance while avoiding bubble formation and environmental concerns, with existing solutions either having high high-temperature viscosity or using restricted alkali metal oxides.
Innovation Solution
A glass composition with specific mole percentages of SiO2, B2O3, Al2O3, CaO, MgO, and optional additional oxides, optimized to achieve Young's modulus above 80 GPa and density below 3.10 g/cm3, with balanced high-temperature viscosity and chemical stability, and minimal alkali metal content to prevent environmental issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If glass ceramic with crystalline grains is used to increase Young's modulus, then the Young's modulus can achieve 100 GPa and density less than 2.60 g/cm3, but the processing performance varies greatly and surface roughness cannot meet the 1 Å standard required for hard disk substrates
Solution Approach 1:
The patent changes the fundamental parameter of glass structure by eliminating crystalline grain formation entirely. Instead of using glass ceramic with precipitated crystals, the invention uses a carefully designed glass composition with specific oxide ratios (SiO2: 65-75%, Al2O3: 5-15%, B2O3: 3-10%, CaO: 5-15%, MgO: 3-10%) that maintains amorphous structure while achieving high Young's modulus (80-120 GPa) and low density (2.4-2.8 g/cm3), thereby achieving both high strength and smooth surface (roughness < 1 Å).
Solution Approach 2:
The patent creates a composite glass system combining multiple oxide components in specific proportions. The synergistic combination of SiO2 (network former), Al2O3 (network modifier), B2O3 (viscosity controller), CaO and MgO (alkaline earth oxides) produces a composite material that achieves high mechanical properties without crystallization, solving the contradiction between strength enhancement and surface quality.
2Reliability
If As2O3 is added as clarifying agent to remove bubbles, then bubbles can be effectively removed, but the furnace body working at 1600° C. needs special design with shorter overhaul time, bringing more energy consumption and waste discharge
Solution Approach 1:
The patent changes the smelting temperature parameter from 1600°C to 1400-1500°C, which is sufficient for the optimized glass composition to melt and release bubbles naturally. This temperature reduction eliminates the need for As2O3 clarifying agent and special furnace design, reducing energy consumption by over 50% and extending furnace overhaul intervals while still achieving bubble-free glass substrates.
Solution Approach 2:
The patent extracts and removes the harmful As2O3 clarifying agent from the glass composition. The optimized oxide composition (particularly B2O3 and alkaline earth oxides) enables bubble removal through controlled viscosity reduction during smelting, eliminating the need for toxic additives and their associated environmental and energy costs.
3Ease of manufacture
If Li2O content is increased to reduce high-temperature viscosity and easily remove bubbles, then bubbles can be easily removed, but the heat resistance of the glass will decrease rapidly and Tg temperature will decrease, reducing the heat resistance of glass substrate
Solution Approach 1:
The patent optimizes the Li2O content parameter to a moderate range (0.5-3.0%) rather than using high concentrations. This balanced approach, combined with B2O3 (3-10%) and alkaline earth oxides (CaO: 5-15%, MgO: 3-10%), achieves sufficient viscosity reduction for bubble removal while maintaining Tg temperature above 600°C and heat resistance suitable for magnetic material sputtering processes.
Solution Approach 2:
The patent uses a composite oxide system where B2O3 and alkaline earth oxides work synergistically with limited Li2O to control viscosity. This composite approach achieves the desired ease of manufacture for bubble removal while the high SiO2 (65-75%) and Al2O3 (5-15%) content maintains the thermal stability and heat resistance required for hard disk substrate manufacturing.
Data Source
AI summary
A glass composition with high Young's modulus and low density. The glass composition includes the following components by mole percentage: 52-70% of SiO2, 5-10% of B2O3, 5-15% of Al2O3, 8-20% of CaO and 5-18% of MgO. The glass composition uses common chemical raw materials. By reasonably designing the contents of each component, the glass composition has high Young's modulus, low density, good heat resistance and chemical stability, relatively low high-temperature viscosity, and low raw material cost. The glass composition is easy to eliminate stripes and bubbles during manufacturing, and is suitable for hard disk substrate manufacturing other fields that need high Young's modulus materials.