Trailing Air Flow Dam and Sub-ambient Cavity for Hard Disk Head
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Solution Overview
Problem
Magnetic hard disk drives face challenges in maintaining optimal flying height and reducing lubricant accumulation on air bearing surfaces, which affects tribological performance, leading to potential reading or writing errors and reduced reliability.
Innovation Solution
The design incorporates a slider with an air bearing surface featuring a trailing air flow dam and sub-ambient pressure cavities, which helps maintain a consistent flying height and reduces debris accumulation by creating pressure gradients that prevent lubricant and contamination from adhering to the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the flying height is reduced to increase areal density, then data storage capacity is improved, but tribological performance deteriorates leading to increased wear and friction
Solution Approach 1:
The air bearing surface is segmented into multiple functional zones including a leading edge region, a trailing edge region, and intermediate regions. Each zone has specific geometric features (convexities, concavities, dams) that create localized pressure distributions to control air flow and reduce lubricant accumulation at critical areas.
Solution Approach 2:
Different regions of the air bearing surface are given different geometric properties - the leading edge has convexities to generate positive pressure, the trailing edge has concavities and dams to create negative pressure zones. This local differentiation optimizes both flying height control and lubricant management in specific areas.
2Measurement precision
If the flying height is reduced to improve reading and writing capability, then transducer performance is improved, but debris accumulation on the air bearing surface increases
Solution Approach 1:
The design extracts and removes accumulated lubricant and debris from the air bearing surface by creating pressure gradients that drive contaminants toward designated accumulation zones (concave regions) where they can be contained and periodically removed, preventing them from interfering with transducer operations.
Solution Approach 2:
The air bearing geometry acts as an intermediary mechanism that mediates between the slider and disk surface, using controlled air pressure fields to prevent direct contact between debris particles and critical surfaces, thereby protecting the transducer while maintaining low flying height.
3Reliability
If lubricant is applied to reduce friction and wear, then tribological performance is improved, but lubricant accumulation on the air bearing surface occurs leading to flying height degradation
Solution Approach 1:
The design converts the harmful effect of lubricant accumulation into a beneficial feature by creating designated accumulation zones (concave regions with dams) where lubricant is intentionally directed and contained. This prevents lubricant from spreading to critical areas while maintaining adequate lubrication at contact zones.
Solution Approach 2:
The air bearing geometry uses pneumatic pressure gradients created by convexities and concavities to control the distribution and removal of lubricant films. Positive pressure zones push lubricant away from critical areas, while negative pressure zones collect and contain excess lubricant, maintaining stable flying height.
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 enhances the tribological performance by stabilizing flying height and reducing debris accumulation, thereby improving the reliability and longevity of magnetic hard disk drives.
Implementation Method 1
The magnetic transducer is typically supported in very close proximity to the magnetic disk by a hydrodynamic air bearing. As the motor rotates the magnetic disk, the hydrodynamic air bearing is formed between an air bearing surface of the slider of the head, and a surface of the magnetic disk.
Implementation Method 2
The design incorporates a slider with an air bearing surface featuring a trailing air flow dam and sub-ambient pressure cavities, which helps maintain a consistent flying height and reduces debris accumulation by creating pressure gradients that prevent lubricant and contamination from adhering to the surface.
Data Source
AI summary
A head includes a transducer and a slider having an air bearing surface (ABS) and a trailing face. The slider has an overcoat layer that includes the trailing face and that overcoats the transducer. The ABS includes a trailing pad having a major surface adjacent the transducer, with the major surface lying in a primary plane. The ABS also includes a sub-ambient pressure cavity disposed upstream of the overcoat layer and being recessed from the primary plane by a cavity depth in the range 0.8 to 2 microns. The overcoat layer includes a trailing air flow dam being recessed from the primary plane by a step depth in the range 0.05 to 0.5 microns. The overcoat layer also includes a corner region recessed from the primary plane by at least the cavity depth.