Electrostatic Slider Fly Height Measurement
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Solution Overview
Problem
Current methods for measuring the fly height of magnetic heads in hard disk drives are either invasive, prone to wear, or require a "touch-down" process, which is time-consuming and uncertain, especially in portable devices where ambient pressure and temperature frequently change.
Innovation Solution
A non-contact method using electrostatic force to measure the fly height by applying a series of distinct voltages between the slider and the magnetic data storage medium, recording read-back signals, and calculating the coefficients of a quadratic equation to determine the fly height, without the need for a transparent disk or touch-down process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical fly height measurement is used, then measurement precision is improved, but the risk of electrostatic discharge damage to transducers increases
Solution Approach 1:
The patent replaces the optical measurement system with an electrostatic measurement system. Instead of using light reflection and interference patterns to measure fly height, the invention applies electrostatic force between the slider and disk, measuring the force required to maintain a specific fly height. This substitution eliminates the need for transparent disks and optical components that generate electrostatic discharge, while providing continuous measurement capability without contact.
Solution Approach 2:
The patent introduces electrostatic force as an intermediary mechanism to measure fly height indirectly. Rather than directly observing the physical gap between slider and disk through optical means, the system uses the electrostatic interaction field between the two components as a mediator to infer fly height measurements, avoiding direct contact and electrostatic discharge hazards.
2Measurement precision
If touch-down process is used for fly height measurement, then measurement reference is established, but slider-disk interface wear increases and measurement time increases
Solution Approach 1:
The patent performs fly height measurements continuously during normal slider operation before any wear occurs. By establishing measurement baseline data during the initial design and manufacturing phases, and continuously monitoring during operation, the system eliminates the need for periodic touch-down procedures to re-establish reference points, saving time and preventing wear.
Solution Approach 2:
The measurement system uses the slider's own operational state to provide measurement references. By continuously monitoring electrostatic force characteristics during normal flying operations, the system self-calibrates and maintains measurement accuracy without requiring external intervention or contact-based reference establishment procedures.
3Measurement precision
If touch-down process is used for fly height measurement, then reference fly height is obtained, but slider-disk interface wear increases
Solution Approach 1:
The patent replaces mechanical contact-based reference establishment with electrostatic field-based measurement. By using the electrostatic force characteristics that naturally occur during slider flying operations, the system obtains reference data without mechanical contact, preserving the integrity of the slider-disk interface and eliminating wear-related reliability issues.
4Manufacturing precision
If heater protrusion is used to adjust fly height, then fly height control is improved, but power consumption increases and read-write sensor lifespan decreases
Solution Approach 1:
The patent replaces thermal expansion-based fly height adjustment with electrostatic force-based adjustment. By applying electrostatic force between the slider and disk, the system can precisely control fly height without generating heat, thereby eliminating the power consumption issues and thermal stress on sensors associated with heater-based systems.
Solution Approach 2:
The patent changes the physical parameter used for fly height control from temperature (thermal expansion) to electrostatic force. By controlling the voltage applied between the slider and disk, the system adjusts fly height through electrostatic attraction/repulsion, providing precise control without the energy consumption and thermal damage problems of heater-based systems.
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
Enables frequent, non-destructive monitoring of fly height, reducing wear and tear, and optimizing fly height adjustment with lower power consumption and reduced arcing hazards, improving statistical process control and slider positioning.
Implementation Method 1
a non-contact method using electrostatic force to measure the fly height by applying a series of distinct voltages between the slider and the magnetic data storage medium
Implementation Method 2
an air bearing surface (ABS) formed on the slider body experiences a fluid air flow that provides sufficient lift force to 'fly' the slider and transducer above the disk data tracks
Data Source
AI summary
In a system and method for a non-contact measurement of the fly height of a slider above a magnetic data storage medium using electrostatic force, a slider with a read/write head flies over a magnetic data storage medium. A series of distinct voltages are applied between the slider and the magnetic data storage medium, and corresponding read-back signals are recorded. Using the recorded read-back signals, coefficients for an empirical curve-fit equation are calculated. The coefficients are normalized and converted into a fly height measurement.