Co-Pt-B Sputtering Target Grain Refinement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The brittle B-rich phase in Co—Pt—B-based alloys fractures during cold rolling, leading to cracks that cause arcing and particle generation during sputtering, reducing the yield and stability of magnetic recording medium production.
Innovation Solution
The B-rich phase is intentionally cracked and refined to reduce its grain area to 90 μm2 or less, with a maximum of 2500 cracks/mm2, using a process involving primary and secondary rolling, and optionally adding elements like Cu, Ru, Ta, and Nd to enhance leakage flux density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If cold rolling is performed to increase leakage flux density, then sputtering voltage can be reduced, but cracks are generated in the B-rich phase causing arcing and particle generation
Solution Approach 1:
The patent applies preliminary hot rolling at 800-1100°C before cold rolling to pre-deform the B-rich phase and reduce its brittleness. This preliminary thermal-mechanical treatment modifies the microstructure in advance, allowing subsequent cold rolling to increase leakage flux density without generating harmful cracks that would cause arcing during sputtering
Solution Approach 2:
The patent changes the temperature parameter by performing hot rolling at 800-1100°C before cold rolling. This temperature change transforms the material's mechanical properties, making the B-rich phase less brittle and more ductile, thereby enabling the cold rolling process to achieve the desired leakage flux density without crack formation
2Power
If voltage during sputtering is increased to compensate for low leakage flux density, then discharge can be maintained, but arcing is generated and particles are produced
Solution Approach 1:
The patent applies beforehand cushioning by performing hot rolling treatment before cold rolling to pre-prevent the formation of cracks in the B-rich phase. This preliminary protective treatment ensures that the target material is free from defects that would otherwise cause arcing and particle generation during high-voltage sputtering operations
3Device complexity
If the area of the B-rich phase is increased, then the alloy composition is simplified, but stress concentration increases and crack generation increases
Solution Approach 1:
The patent applies segmentation by dividing the B-rich phase into smaller, dispersed regions through controlled hot rolling at 800-1100°C followed by cold rolling. This segmentation reduces stress concentration in any single B-rich region while maintaining the overall alloy composition simplicity, thereby preventing crack formation
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 stabilizes the sputtering discharge, suppresses arcing, and significantly reduces particle generation, resulting in a high-quality film and improved production yield by maintaining a low maximum magnetic permeability of 50 or less.
Implementation Method 1
A magnetic thin film of a magnetic recording medium such as a hard disk is often produced by sputtering a ferromagnetic sputtering target made from foregoing materials via sputtering
Implementation Method 2
when the Co—Pt—B-based alloy or the like is subject to cold rolling, there is a problem in that the brittle B-rich phase in the alloy is subject to brittle fracture, and cracks are generated
Data Source
AI summary
A sputtering target for a magnetic recording medium, wherein an average grain area of a B-rich phase is 90 μm2 or less. A process for producing a sputtering target for a magnetic recording medium, wherein an alloy cast ingot is subject to heat treatment, thereafter subject to primary rolling which includes at least one pass of cold rolling, thereafter subject to secondary rolling, and machined to prepare a target. The obtained sputtering target for a magnetic recording medium has few cracks in the B-rich phase and has a high leakage flux density, and by using this target, it is possible to stabilize the discharge during sputtering, suppress arcing which occurs from cracks in the B-rich phase, and suppress the generation of particles.