Head Slider Localized Heating for Glide Height Measurement
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Solution Overview
Problem
Existing glide height checking apparatuses face challenges in accurately measuring glide height below 4 nm due to variations in flying force and pressing load, leading to measurement errors caused by asperities on the air bearing surface of head sliders.
Innovation Solution
The implementation of a head slider with a plurality of heaters that can be independently controlled to locally heat and planarize the air bearing surface, combined with a current control section that adjusts heating based on asperity information, allowing the head slider to maintain a consistent flying height and accurately detect collisions with disk projections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the air bearing surface width is increased to check larger area, then productivity is improved, but measurement precision deteriorates due to asperity-induced sensor sensitivity variation
Solution Approach 1:
The patent divides the air bearing surface into multiple localized heating regions, each with independent temperature control. This allows different parts of the surface to have optimized local properties - heated regions compensate for asperities to maintain uniform sensor sensitivity across the entire wide scanning area, while unheated regions maintain original characteristics.
2Measurement precision
If flying height is reduced to less than 4 nm to achieve accurate glide height checking, then measurement precision is improved, but reliability deteriorates due to increased contact risk with disk projections
Solution Approach 1:
The patent dynamically adjusts the temperature parameter of the air bearing surface through localized heating. By changing the thermal state of the surface, the air viscosity and bearing characteristics are modified, enabling stable flight at ultra-low heights below 4 nm while maintaining measurement accuracy and preventing contact with disk projections.
3Device complexity
If individual head sliders have varying flying force due to processing accuracy, then device complexity is improved (no need for perfect uniformity), but measurement precision deteriorates due to flying height variation among individuals
Solution Approach 1:
The patent implements a feedback mechanism where sensor data from the air bearing surface is used to determine localized heating amounts. This closed-loop control compensates for individual variations in flying force and processing tolerances, maintaining consistent flying height and measurement precision across all head sliders without requiring perfect manufacturing uniformity.
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 solution enables precise glide height checking even with asperities, ensuring accurate measurements and increased scanning area by maintaining a uniform flying height and sensor sensitivity, thereby overcoming the limitations of previous technologies.
Implementation Method 1
a heater locally heating a corresponding region of the air bearing surface... when a heater is applied with a current to generate heat, and a part of the air bearing surface is heated by the heat, the part is projected due to thermal expansion
Implementation Method 2
flying force induced on the air bearing surface of the head slider is balanced with resultant force (pressing load) of gravity of the head slider and spring load of a suspension
Data Source
AI summary
The head slider has a plurality of heaters each heating a corresponding region of the ABS, and a sensor detecting collision of the ABS with a projection on a surface of the magnetic disk. Currents supplied to the respective heaters are controlled and produce heats independently of one another. The heats produce projections on the corresponding regions of the ABS, respectively. The ABS with asperity can be planarized through appropriately controlling magnitude of the currents supplied to the heaters. Thus, the variation of a sensor output depending on asperity of the ABS is effectively reduced. Another head slider has a heater locally heating a corresponding region of the ABS. The heater has a structure where a central portion is away from the ABS compared with end portions, or a structure where calorific power of a central portion is smaller than that of each of end portions. Thus, overall projection shape becomes flat.