Thin-Film Magnetic Head WATE Reduction via Connecting Layer
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Solution Overview
Problem
Conventional perpendicular magnetic recording heads with backing coils suffer from issues like adjacent track erasure and wide area track erasure due to magnetic flux leakage, and the manufacturing process is complex, with potential heat-related damage from the backing coil.
Innovation Solution
A thin-film magnetic head design without a backing coil, featuring a main magnetic pole layer, a write shield layer, a gap layer, and a thin-film coil laminated on a substrate, with a connecting magnetic layer to redirect magnetic flux and a single-layer structure for the thin-film coil, enhancing magnetic flux management and reducing manufacturing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a backing coil is provided to improve WATE, then wide area track erasure is reduced, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent extracts and removes the backing coil from the head structure, replacing it with a simplified magnetic pole piece design that achieves WATE reduction without requiring the additional coil component. This eliminates the complexity associated with winding and positioning the backing coil while maintaining the essential WATE mitigation function.
Solution Approach 2:
The patent merges the WATE reduction function into the main magnetic pole piece structure itself, rather than using a separate backing coil component. The magnetic pole piece is designed with specific geometric features that inherently control magnetic flux distribution, combining multiple functions into a single integrated component.
2Reliability
If a backing coil is provided to improve WATE, then wide area track erasure is reduced, but manufacturing process complexity increases
Solution Approach 1:
By removing the backing coil from the design, the patent eliminates the complex manufacturing steps required to wind, position, and secure the additional coil. The manufacturing process is simplified to focus on precision machining of the magnetic pole piece geometry, which is more straightforward than coil assembly.
Solution Approach 2:
The patent combines the WATE reduction functionality directly into the magnetic pole piece manufacturing process, allowing it to be produced in the same machining operations as the main head components. This integration eliminates separate manufacturing steps for the backing coil, reducing overall process complexity.
3Reliability
If a backing coil is provided to improve WATE, then wide area track erasure is reduced, but heat-related damage risk increases
Solution Approach 1:
By extracting and removing the backing coil, the patent eliminates the source of additional heat generation that would occur from current flow through the coil. This reduces the overall thermal load on the head components and recording medium, preventing heat-related damage while maintaining WATE performance through geometric design.
4Power
If the thin-film coil is wound around the magnetic pole layer, then recording magnetic field is generated, but adjacent track erasure occurs due to skew
Solution Approach 1:
The patent applies local quality by designing the magnetic pole piece with non-uniform geometry - specifically, the pole piece has a narrower width at the medium-facing surface compared to the rear end. This localized geometric variation controls the magnetic flux distribution, concentrating the field where needed while reducing lateral spread that causes ATE.
Solution Approach 2:
The patent employs asymmetry in the magnetic pole piece cross-section, creating a tapered profile that is wider at the rear and narrower at the medium interface. This asymmetric geometry optimizes the magnetic field pattern, directing flux perpendicular to the medium surface and minimizing the skew that leads to adjacent track erasure.
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 design effectively improves wide area track erasure without a backing coil, reducing the risk of heat-related damage and simplifying the manufacturing process, while maintaining high recording density and signal-to-noise ratio.
Implementation Method 1
a thin-film coil which generates a magnetic field pass through inside of the main magnetic pole layer
Implementation Method 2
a phenomenon that data recorded on the track disposed at a position distanced by about several μm to several tens of μm from the track where data will be written is erased is WATE. WATE is caused by the fact that a part of the magnetic flux emitted from the main magnetic pole layer and then flowing back to the return magnetic pole layer passes through the shield layer formed in the reproducing head and is emitted from the medium-opposing surface.
Data Source
AI summary
A thin-film magnetic head includes a main magnetic pole layer, write shield layer, gap layer, and thin-film coils, which are laminated on a substrate. A return magnetic pole layer is spaced from the medium-opposing surface on the side opposite to the write shield layer with the main magnetic pole layer intervening therebetween. A connecting magnetic layer is formed using a magnetic material to connect the return magnetic pole layer to the write shield layer on the side closer to the medium-opposing surface than is the thin-film coil. The thin-film coil is wound as a flat spiral around the write shield layer. A part of the thin-film coil wound as the flat spiral is disposed only at a position distanced from the substrate than is the main magnetic pole layer.