Aluminum Alloy Magnetic Disk Substrate Composition and Plating
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Solution Overview
Problem
Aluminum alloy magnetic disks face challenges in reducing disk flutter and abnormal portions on electroless Ni—P plated surfaces, which are contradictory issues that existing technologies struggle to address simultaneously, especially with the need for thinner materials to increase storage capacity and data transfer rates in HDDs.
Innovation Solution
The introduction of an aluminum alloy substrate with specific compositions, including 0.1 to 3.0 mass % Fe, 0.005 to 1.000 mass % Cu, and 0.005 to 1.000 mass % Zn, and a compound removal step using a mixed solution of HNO3 and HF before electroless Ni—P plating, to disperse compounds and reduce nodules on the surface, thereby minimizing disk flutter and defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the thickness of aluminum alloy base material is reduced to increase storage capacity, then the storage capacity per magnetic disk increases, but the rigidity decreases causing increased disk flutter
Solution Approach 1:
The patent changes the chemical composition parameters of the aluminum alloy by adding specific amounts of Fe (0.01-3.0 mass%), Cu (0.01-1.0 mass%), and Zn (0.01-1.0 mass%). This compositional modification allows the use of thinner base materials (0.5-2.0 mm) while maintaining sufficient rigidity to reduce disk flutter, thus resolving the contradiction between increasing storage capacity and maintaining structural strength.
2Strength
If Fe is added to aluminum alloy substrate to reduce disk flutter, then the rigidity improves, but the number of abnormal portions on electroless Ni-P plated surface increases
Solution Approach 1:
The patent optimizes the Fe content parameter within a specific range (0.01-3.0 mass%) and combines it with Cu and Zn additions. This controlled parameter change allows achieving sufficient rigidity while limiting the formation of excessive compounds that would cause plating defects, thus resolving the contradiction between improving strength and maintaining plating surface quality.
Solution Approach 2:
The patent creates a composite aluminum alloy system by combining Al with Fe, Cu, and Zn elements. This composite material approach allows the Fe to provide rigidity benefits for reducing disk flutter, while the Cu and Zn elements help control the formation and distribution of compounds, thereby maintaining good plating surface quality despite the presence of Fe.
3Strength
If compounds are densely distributed on aluminum alloy substrate surface, then disk flutter is reduced, but the number of nodules on outer peripheral surface increases
Solution Approach 1:
The patent carefully controls the concentration and distribution of alloying elements (Fe: 0.01-3.0 mass%, Cu: 0.01-1.0 mass%, Zn: 0.01-1.0 mass%) to achieve optimal compound formation. This parameter optimization ensures sufficient compound density for reducing disk flutter while preventing excessive nodule formation on the outer peripheral surface, thus resolving the contradiction between improving rigidity and maintaining surface smoothness.
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 approach effectively reduces disk flutter and abnormal portions on the electroless Ni—P plated surface, enabling thinner magnetic disks with improved storage capacity and increased HDD capacity by enhancing the manufacturing process to achieve smoother surfaces and better plating quality.
Implementation Method 1
a compound removal step of removing compounds on a surface of the disk blank subjected to stress relief heat treatment
Implementation Method 2
electroless plating with Ni—P, which is a hard non-magnetic metal, is performed as undercoat treatment
Data Source
AI summary
An aluminum alloy substrate for a magnetic disk including an aluminum alloy containing 0.1 to 3.0 mass % of Fe, 0.005 to 1.000 mass % of Cu, and 0.005 to 1.000 mass % of Zn, with a balance of Al and inevitable impurities, wherein in an outer peripheral surface thereof, the number of holes having maximum diameters of 10 μm or more is 200/mm2 or less, an aluminum alloy base disk for a magnetic disk and a magnetic disk, using the aluminum alloy substrate, and methods for manufacturing these.