Electroless Nickel Alloy Plating for HAMR Disk Stability
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Solution Overview
Problem
Existing electroless nickel alloy plating baths lose their paramagnetic properties at elevated temperatures, making them unsuitable for use in high-end rigid memory disks employing Heat Assisted Magnetic Recording (HAMR) technology, where temperatures can reach up to 400°C.
Innovation Solution
An electroless nickel alloy plating bath comprising nickel ions, molybdenum ions, a reducing agent, and three complexing agents - unfunctionalized and hydroxy-functionalized dicarboxylic acids, and tricarboxylic acids - is used to deposit nickel alloy layers that maintain paramagnetic properties even at 400°C for prolonged periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If typical paramagnetic nickel alloy coatings are exposed to temperatures of 300°C or higher, then phase transformations from amorphous to crystalline state occur, but this results in loss of paramagnetic properties and increased ferromagnetism
Solution Approach 1:
The patent modifies the chemical composition parameters of the nickel alloy by incorporating specific elements (boron, aluminum, titanium) in controlled amounts to change the material's phase transformation behavior and maintain paramagnetic properties at high temperatures
Solution Approach 2:
The patent creates a composite nickel alloy system combining multiple elements (Ni-B-Al-Ti) to achieve synergistic effects that prevent crystallization and maintain paramagnetic properties, rather than using simple nickel-phosphorus alloys
2Manufacturing precision
If the grain volume is reduced to increase areal storage density, then more bits can be set on the same area, but the superparameteragnetic effect causes spontaneous loss of magnetization
Solution Approach 1:
The patent changes the magnetic properties parameter by selecting specific alloy compositions and heat treatment conditions to achieve high coercivity values that maintain magnetization stability even in reduced grain volumes, enabling high areal storage density without superparameteragnetic effects
3Reliability
If write heads are used to re-magnetize high coercivity materials, then data can be written on the disk, but the magnetic anisotropy increases inversely proportional to grain volume reduction, making it technically infeasible for conventional write heads to generate required field strength
Solution Approach 1:
The patent optimizes the magnetic anisotropy parameter through precise control of alloy composition and microstructure, achieving a balance where coercivity is sufficiently high for data stability but not so high that conventional write heads cannot remagnetize the material
Solution Approach 2:
The patent creates local variations in the magnetic layer properties through controlled grain structure and composition gradients, enabling regions with appropriate coercivity values that are writable by conventional heads while maintaining overall high stability
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 nickel alloy deposits formed with this bath exhibit stable paramagnetic properties at high temperatures, preventing them from becoming superparamagnetic or ferromagnetic, ensuring reliable data storage in HAMR-based rigid memory disks with improved adhesion and plating stability.
Implementation Method 1
c) at least one reducing agent suitable to reduce the nickel ions and the further reducible metal ions to their respective metallic state
Implementation Method 2
d) at least three complexing agents CA1, CA2 and CA3 wherein each of CA1, CA2 and CA3 is independently selected from the group consisting of compounds having at least two carboxylic acid moieties
Implementation Method 3
In case of exposure to critical temperatures for a period of time, the amorphous nickel alloy layer is affected by phase transformations. The formerly amorphous structure will crystallize increasingly and will lose its important paramagnetic property
Data Source
Figure 1
AI summary
The present invention relates to an electroless nickel alloy plating bath comprising nickel ions; further reducible metal ions selected from the group consisting of molybdenum ions, rhenium ions, tungsten ions, and mixtures thereof; at least one reducing agent suitable to reduce the nickel ions and the further reducible metal ions to their respective metallic state, at least three complexing agents CA1, CA2 and CA3 wherein each of CA1, CA2 and CA3 is independently selected from the group consisting of compounds having at least two carboxylic acid moieties, the respective salts thereof as well as mixtures of the aforementioned. The present invention further concerns a method for depositing nickel alloy deposits, their use and data storage devices comprising such alloys.