Ultrafast Touchdown Measurement via Thermal and Voltage Actuation
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Solution Overview
Problem
Current touchdown measurement methods for hard disk drives (HDDs) are time-consuming and cause significant head wear due to prolonged contact during thermal protrusion tests, necessitating a reduction in contact duration for both wear reduction and faster test completion.
Innovation Solution
Implementing a method that combines thermal flyheight control with an electrostatic voltage bias pulse to rapidly actuate the slider into contact with the disk, allowing for ultrafast touchdown measurement with reduced head wear through targeted and localized actuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If thermal protrusion test is performed for touchdown measurement, then clearance estimation is obtained, but head wear increases and test duration extends
Solution Approach 1:
The patent applies periodic pulsed voltage to the TFC heater instead of continuous heating. The pulsed heating cycle allows the head to be actuated toward the disk for measurement, then cooled and retracted, repeating this cycle multiple times to obtain clearance data through averaging. This periodic action reduces the total time the head remains in contact with or near the disk surface, thereby reducing wear while maintaining measurement precision through statistical averaging of multiple pulses.
Solution Approach 2:
The patent applies preliminary voltage pulses to actuate the head toward the disk before the actual measurement is taken. By performing preliminary actuation steps, the system prepares the head position and thermal conditions in advance, allowing the actual measurement to be completed more quickly with reduced contact time. This preliminary action enables the system to establish optimal measurement conditions without requiring prolonged test durations.
2Measurement precision
If thermal protrusion test is performed for touchdown measurement, then clearance estimation is obtained, but head wear increases
Solution Approach 1:
The pulsed heating approach periodically actuates the head toward the disk for brief measurement intervals, then allows cooling and retraction periods. This periodic on-off cycling minimizes the cumulative contact time and thermal exposure of the head to the disk surface, directly reducing wear mechanisms while maintaining measurement accuracy through repeated measurements and averaging across multiple pulse cycles.
Solution Approach 2:
The patent uses high-power pulsed heating to rapidly actuate the head through the flight gap and achieve touchdown measurement in a single brief event rather than through gradual, prolonged heating. This 'rushing through' approach minimizes the time the head spends in the critical near-contact zone, reducing wear exposure while obtaining the necessary clearance data in a single rapid measurement pass.
3Measurement precision
If prolonged contact is used for touchdown measurement, then measurement accuracy is maintained, but productivity decreases
Solution Approach 1:
The system performs multiple rapid pulsed measurements in sequence rather than one prolonged measurement. Each pulse provides a quick clearance estimate, and by averaging results across many pulses, the system achieves high measurement precision. This periodic pulsed approach increases productivity by enabling rapid successive measurements across multiple tracks and zones, significantly increasing test throughput compared to traditional prolonged contact methods.
Solution Approach 2:
The system performs preliminary characterization and preliminary pulses to establish baseline conditions and optimal measurement parameters before conducting the full measurement sequence. This preliminary action allows the main measurement phase to proceed more efficiently with pre-optimized parameters, reducing the time required for each measurement while maintaining accuracy, thereby increasing overall productivity.
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 enables efficient and ultrafast touchdown power mapping across the entire disk, significantly reducing head wear and test duration while maintaining data integrity, particularly beneficial for large form factor drives like cold storage systems.
Implementation Method 1
supplying power to the thermal flyheight control (TFC) heater, which causes a thermal protrusion of the read/write head location bringing it closer to the disk
Implementation Method 2
an electrostatic voltage bias pulse is applied between the slider body and the disk to actuate the slider into contact with the disk
Data Source
AI summary
A method, apparatus, and system are provided for implementing touchdown measurement using thermal and voltage actuation for hard disk drives (HDDs). The touchdown measurement uses a constant power applied to a thermal flyheight control (TFC) and an electrostatic voltage bias pulse is applied between the slider body and the disk to actuate the slider into contact with the disk.