Thermal Fly-Height Calibration for Data Storage Sliders
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Solution Overview
Problem
Existing data storage devices face challenges in accurately calibrating Thermal Fly-height Control (TFC) for write elements due to manufacturing variations and localized heating during write operations, leading to increased error rates and potential damage from improper fly height control.
Innovation Solution
The system employs dual heating elements for the slider, with calibrated power settings based on electrostatic force adjustments using Interface Voltage Control (IVC) to accurately control fly height, accounting for manufacturing variations and localized heating effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If thermal expansion is used to reduce fly height for increased areal density, then data storage density is improved, but manufacturing variations and localized heating cause imprecise fly height control
Solution Approach 1:
The patent implements a feedback mechanism where the read element continuously monitors the fly height by reading signals from the magnetic disk. Based on this feedback, the system adjusts the power supplied to the heating element to maintain the desired fly height. This closed-loop control compensates for manufacturing variations and localized heating effects, ensuring precise fly height control while maintaining high areal density.
Solution Approach 2:
The patent dynamically changes the power parameter supplied to the heating element based on feedback from the read element. By adjusting the heating power in real-time, the system compensates for manufacturing variations and localized heating, maintaining precise fly height control while achieving high areal density through thermal expansion.
2Quantity of substance
If fly height is reduced to place magnetic bits closer together, then areal density is improved, but error rates increase due to imprecise control
Solution Approach 1:
The read element provides continuous feedback on fly height, enabling the system to maintain precise control even at reduced fly heights. This feedback mechanism allows the system to operate reliably at lower fly heights where areal density is improved, preventing the increase in error rates that would otherwise occur due to imprecise control.
3Quantity of substance
If thermal expansion is applied to the slider, then fly height is reduced for better data density, but localized heating during write operations complicates control
Solution Approach 1:
The read element acts as an intermediary that indirectly measures the fly height at the write element location. Instead of directly measuring or controlling the write element fly height, the system uses the read element's feedback signal to infer and control the thermal expansion effect, simplifying the control mechanism despite localized heating complications.
4Ease of manufacture
If fly height control is not precisely calibrated, then manufacturing simplicity is maintained, but slider contact with disk causes damage and reduced lifespan
Solution Approach 1:
The system performs self-calibration using the read element's feedback signal. During normal operation, the read element continuously provides information about fly height, allowing the system to automatically adjust and maintain optimal spacing without requiring external calibration procedures. This self-service approach maintains manufacturing simplicity while ensuring reliable slider operation and extended lifespan.
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 provides precise fly height control, reducing error rates and extending the life of the slider by minimizing contact with the magnetic disk, thereby maintaining optimal areal density.
Implementation Method 1
one or more heating elements in the slider are powered to cause thermal expansion of the slider, or at least the portions of the slider including the write element and/or the read element
Implementation Method 2
A first power is supplied to the second heating element that causes thermal expansion of the second portion of the slider to make contact with the magnetic disk without applying a first voltage to the slider. When applied to the slider, the first voltage causes a change in the first distance by causing an electrostatic force between the slider and the magnetic disk.
Data Source
AI summary
A Data Storage Device (DSD) includes a disk and a slider. A change in distance between the slider and the disk is determined by applying a first voltage to the slider that increases an electrostatic force between the slider and the disk. The change in distance is approximately the same across a surface of the slider facing the disk. A first power supplied to the heating element is determined that causes thermal expansion of a portion of the slider until making disk contact without applying the first voltage. A second power supplied to the heating element is determined that causes a reduced thermal expansion of the portion until making disk contact while applying the first voltage. A first power setting is calibrated based on a correlation between the determined change in distance and a difference between the first and second powers.