Bi-layer Wrap Around Shield Dissimilar Widths
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Solution Overview
Problem
The lapping process for magnetic write heads with bi-layer wrap around shields results in different material removal rates for high and low magnetic moment materials, leading to protrusion of the high magnetic moment inner layer, which reduces clearance and increases the potential for head-to-disk contact.
Innovation Solution
A magnetic write head design with a wrap around shield featuring a first magnetic layer proximate to the main write pole and a second magnetic layer with a wider width, where the back edges of both layers are coplanar, reducing protrusion and maintaining the throat height, thereby minimizing the risk of head-to-disk contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a bi-layer wrap around shield with high magnetic moment inner layer and lower magnetic moment outer layer is used, then the write field gradient is increased and signal to noise ratio is improved, but the high magnetic moment inner layer protrudes from the air bearing surface during lapping, reducing clearance and increasing head-to-disk contact risk
Solution Approach 1:
The patent applies local quality by giving different widths to the inner and outer magnetic layers of the wrap around shield. Specifically, the high magnetic moment inner layer has a first width while the lower magnetic moment outer layer has a second width that is greater than the first width. This local differentiation allows the inner layer to maintain its magnetic performance while the outer layer extends wider to prevent protrusion during lapping, thus resolving the contradiction between write field gradient and head-to-disk contact risk
Solution Approach 2:
The patent employs asymmetry by designing the bi-layer wrap around shield with non-uniform layer widths. The inner magnetic layer and outer magnetic layer have asymmetric dimensions where the outer layer width exceeds the inner layer width. This asymmetric design ensures that during the lapping process, the wider outer layer compensates for differential material removal rates, preventing the inner layer from protruding while maintaining the desired magnetic field gradient
2Manufacturing precision
If the pole tip width is reduced to control track width, then the track width is precisely controlled, but the write field strength is reduced
Solution Approach 1:
The patent uses composite materials by implementing a bi-layer wrap around shield structure where the inner layer has high magnetic moment and the outer layer has lower magnetic moment. This composite magnetic structure allows the pole tip to maintain a narrow width for precise track control while the bi-layer shield configuration enhances and concentrates the write field, compensating for the reduced field strength that would otherwise result from the narrow pole tip
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 coplanar back edges of the magnetic layers reduce the protrusion area of the first magnetic layer out of the air bearing surface, enhancing the clearance and reducing the potential for head-to-disk contact, thus improving the operational stability and performance of the magnetic write heads.
Implementation Method 1
The use of bi-layer wrap around shields increases the write field gradient of the main write pole when the shield comprises a lower magnetic moment outer layer surrounding a higher magnetic moment inner layer proximate to the main write pole. The increased write field gradient yields sharper magnetic transitions on the disk
Implementation Method 2
A lapping process is used to form the ABS of a slider, and more particularly, the ABS of the write head. Lapping removes material from the ABS of the slider until specific design parameters of the write head are reached
Data Source
AI summary
Magnetic write heads and corresponding fabrication methods for bi-layer wrap around shields resulting in dissimilar shield layer widths are disclosed. A gap structure is formed around a main write pole for a magnetic write head. A wrap around shield for the main write pole is fabricated to include a first magnetic layer proximate to the main write pole and a second magnetic layer on the first magnetic layer. A width of the first magnetic layer is less than the width of the second magnetic layer, and back edges of the first and second magnetic layers are coplanar. Further, a throat height of the wrap around shield is maintained between the first and the second magnetic layers because their back edges are coplanar.