Aluminum Alloy Substrate with NiP Plating for Hard Disk Drive Fluttering
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Solution Overview
Problem
Magnetic recording medium substrates face challenges in increasing storage density and reducing fluttering, which affects the stability of hard disk drives, especially with the use of aluminum alloy substrates, where thinning leads to instability and requires additional gas filling to mitigate fluttering.
Innovation Solution
A magnetic recording medium substrate with an aluminum alloy composition of 9.5-11% Si, 0.45-0.90% Mn, 0.32-0.38% Zn, and 0.01-0.05% Sr, combined with a NiP plating film of 7 μm or more, achieving a Young's modulus of 79 GPa or more, to enhance machinability and reduce fluttering without the need for helium gas filling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the thickness of the aluminum alloy substrate is made thinner to increase the number of magnetic recording media stored inside the drive case, then the memory capacity per unit volume increases, but the substrate generates fluttering which makes stable reading difficult
Solution Approach 1:
The patent changes the chemical composition parameters of the aluminum alloy substrate by precisely controlling the content of Si (7.0-11.0 mass%), Mn (0.05-1.0 mass%), Zn (0.05-1.0 mass%), and Sr (0.003-0.05 mass%). This compositional parameter change increases the Young's modulus of the substrate, thereby reducing fluttering even when the substrate thickness is reduced to 0.7-1.27 mm, allowing 6 or more substrates to be stored while maintaining reading stability
Solution Approach 2:
The patent creates a composite material system by combining aluminum alloy substrate with specific compositional characteristics (high Si and Mn content) and NiP plating film. This composite approach achieves both thinness (reduced thickness) and high rigidity (Young's modulus ≥79 GPa), resolving the contradiction between quantity increase and reliability maintenance
2Quantity of substance
If the thickness of the aluminum alloy substrate is made thinner, then more substrates can be stored inside the drive case, but the machinability and manufacturing cost become problematic
Solution Approach 1:
The patent optimizes the chemical composition parameters of the aluminum alloy to achieve a balance between thinness and machinability. By controlling Si content at 7.0-11.0 mass% and Mn content at 0.05-1.0 mass%, the substrate achieves sufficient strength for thin dimensions (0.7-1.27 mm) while maintaining good machinability through the specific alloying elements that affect cutting tool wear and chip formation
3Reliability
If helium gas is filled inside the drive case to reduce fluttering, then thinner aluminum alloy substrates can be used, but the manufacturing cost increases
Solution Approach 1:
The patent extracts the fluttering reduction function from the external environment (helium gas filling) and transfers it to the substrate itself through compositional modification. By increasing the Young's modulus through specific alloying (Si: 7.0-11.0 mass%, Mn: 0.05-1.0 mass%), the substrate inherently resists fluttering without requiring helium gas, thereby eliminating the additional manufacturing cost while maintaining reliability
Solution Approach 2:
The substrate serves itself by reducing fluttering through its own modified composition rather than relying on external helium gas filling. The specific alloying elements (Si, Mn, Zn, Sr) enable the thin substrate to maintain high rigidity and resist fluttering on its own, making the system self-sufficient and cost-effective
Data Source
AI summary
A magnetic recording medium substrate is provided in which a NiP type plating film is formed on a surface of an aluminum alloy substrate that includes Si in a range of 9.5 mass % or more and 11.0 mass % or less, Mn in a rage of 0.45 mass % or more and 0.90 mass % or less, Zn in a range of 0.32 mass % or more and 0.38 mass % or less, Sr in a range of 0.01 mass % or more and 0.05 mass % or less. In the alloy structure of the aluminum alloy substrate, an average particle diameter of Si particles is 2 μm or less, the film thickness of the NiP type plating film is 7 μm or more. An outer diameter of the magnetic recording medium substrate is 53 mm or more, the thickness is 0.9 mm or less, and the Young's modulus is 79 GPa or more.