Effect of Slider Bias Voltage and Humidity on Wear and Contact Potential

2016 ◽  
Author(s):  
Karcher Morris ◽  
Liane Matthes ◽  
Frederick E. Spada ◽  
Andrey Ovcharenko ◽  
Bernhard E. Knigge ◽  
...  
Keyword(s):  
Bias Voltage ◽  
Electrostatic Force ◽  
Flying Height ◽  
Head Disk Interface ◽  
Kelvin Probe ◽  
Contact Potential ◽  
Disk Interface ◽  
Height Control ◽  
Before And After ◽  
Kelvin Probe Method

The effect of slider bias voltage and humidity on wear at the head/disk interface is investigated. Wear of thermal flying height control sliders is studied as a function of head/disk bias voltage, relative humidity, and heater power. The electrostatic force and the contact potential at the head/disk interface is monitored before and after head wear using the noncontact Kelvin probe method.

A Method to Reduce Head-Disk Interface (HDI) Degradation Risk During Thermal Asperity (TA) Mapping in a Hard Disk Drive

2020 ◽  
Author(s):  
Abhishek Srivastava ◽  
Rahul Rai ◽  
Karthik Venkatesh ◽  
Bernhard Knigge
Keyword(s):  
Hard Disk Drive ◽  
Bias Voltage ◽  
Disk Drive ◽  
Test Time ◽  
Head Disk Interface ◽  
Disk Interface ◽  
Height Control ◽  
Contact Sensor ◽  
Fly Height ◽  
Sample Set

Abstract One of the issues in thermal asperity (TA) detection using an embedded contact sensor (ECS) is the degradation caused to the read/write elements of the head while interacting with the TA. We propose a method to reduce such head-disk interaction (HDI) during TA detection and classification by flying higher at low thermal fly-height control (TFC) power, which minimizes the interaction of the TA with the head. The key idea is to scan the head at higher fly height, but with higher ECS bias voltage. Initial experiments have shown that the TA count follows a negative cubic relationship with the backoff at various bias levels, and that it follows a square relationship with bias at various backoff levels. Using a sample set, the calibration curves i.e. the golden relationship between these parameters can be established. Using these, one can start the TA detection at the highest backoff and high ECS bias, and start to estimate the nominal TA count. By mapping out these TAs and ensuring the head does not fly over them again to prevent HDI, the fly height can then be lowered, and the rest of the TA cluster can be scanned. Following this method iteratively, the entire TA cluster can be mapped out with minimal interaction with the head. Although this method entails an increase in the test time to detect and map all TAs, compared to detecting them with TFC being on, this can help improve the reliability of the drive by protecting the sensitive read/write elements especially for energy assisted recording from HDI.

Effect of Head–Disk Interface Biasing and Relative Humidity on Wear of Thermal Flying Height Control Sliders

2017 ◽  
Vol 65 (2) ◽  
Author(s):  
Liane M. Matthes ◽  
Frederick E. Spada ◽  
Andrey Ovcharenko ◽  
Bernhard E. Knigge ◽  
Frank E. Talke
Keyword(s):  
Relative Humidity ◽  
Flying Height ◽  
Head Disk Interface ◽  
Disk Interface ◽  
Height Control ◽  
Thermal Flying Height Control

Heater AC Voltage Induced Flying Height Modulations

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Wei Hua ◽  
Kang Kee Ng ◽  
Shengkai Yu ◽  
Weidong Zhou ◽  
Kyaw Sett Myo
Keyword(s):  
Electrostatic Force ◽  
Laser Doppler Vibrometer ◽  
Drive Level ◽  
Flying Height ◽  
Air Bearing ◽  
Skew Angle ◽  
Frequency Method ◽  
Disk Interface ◽  
Height Control ◽  
Disk Contact

For a thermal flying-height control (TFC) slider, its heater is usually provided with DC voltage. However, recently, both DC and AC voltages may be supplied to the heater. Unlike supplying AC voltage to the slider and disk in the past, the AC voltage to the heater will not only produce a thermal protrusion on the slider, but also leaves a part of the AC voltage on the slider/disk interface. The voltage acts as the electrostatic force and can be used for further control of the slider, even in the drive level. Simulations show that the flying height modulation is highly related to the AC frequency. By sweeping the AC frequencies while monitoring the flying height and pitch angle modulations, the first and second pitch modes of air bearing frequencies can be experimentally obtained without slider/disk contact. The roll mode frequency is also obtainable when the skew angle is not zero. The simulation results agree well with the experimental results obtained by a laser Doppler vibrometer (LDV). Therefore, the sweeping AC frequency method provides a practical scheme to obtain the air bearing frequencies without any slider/disk contact, even in the drive level.

Investigation of the Contact Potential of the Head-Disk Interface Using Kelvin Probe Measurements

2018 ◽  
Author(s):  
Tan D. Trinh ◽  
Frederick E. Spada ◽  
Andrey Ovcharenko ◽  
Frank E. Talke
Keyword(s):  
Acoustic Emission ◽  
Disk Surface ◽  
Head Disk Interface ◽  
Kelvin Probe ◽  
Contact Potential ◽  
Recording Head ◽  
Disk Interface ◽  
Dc Offset ◽  
Offset Voltage ◽  
Probe Measurements

The contact potential across the head-disk interface is investigated. AC voltage was applied to the disk surface using a mercury connector located at the top of the spindle, keeping the recording head grounded. The acoustic emission (AE) and touchdown sensor (TDS) amplitude was measured as a function of the DC offset voltage to determine the contact potential across the head-disk interface at which the AE and TDS signals, respectively, becomes a minimum. The contact potential across the head-disk interface is studied as a function of temperature, relative humidity, and wear of the head-disk interface.

In-Situ Contact Potential Measurement in Hard Disk Drives Using Head Disk Interface Voltage Control

2014 ◽  
Author(s):  
Aravind N. Murthy ◽  
Remmelt Pit ◽  
Karl A. Flechsig
Keyword(s):  
Hard Disk Drives ◽  
Hard Disk ◽  
Flying Height ◽  
Disk Drives ◽  
Head Disk Interface ◽  
Contact Potential ◽  
Potential Measurement ◽  
Dc Voltage ◽  
Disk Interface ◽  
Voltage Bias

There is an inherent contact potential difference between the head and the disk surfaces in hard disk drives (HDD’s). Current HDD’s use thermal fly-height control (TFC) during read/write operations. In this study, we show a method to determine the contact potential for the head disk interface (HDI) using TFC technology. We utilize TFC to measure the flying height of the slider via touchdown power by applying a DC voltage bias to either the head or the disk or both. The DC voltage condition where the TFC clearance is maximized corresponds to the balancing of the HDI contact potential. In other words, the opposite polarity of that DC voltage bias condition is the HDI contact potential. Additionally, we show that the contact potential of HDI can be determined by either applying the DC voltage bias to the head or to the disk.

scholarly journals Particle Contamination on a Thermal Flying-Height Control Slider

2009 ◽  
Author(s):  
Nan Liu ◽  
David B. Bogy
Keyword(s):  
Disk Drive ◽  
Flying Height ◽  
Head Disk Interface ◽  
Direction Parallel ◽  
Disk Interface ◽  
Height Control ◽  
Thermophoretic Force ◽  
Thermal Flying Height Control ◽  
Particle Contamination ◽  
Saffman Lift Force

Particle contamination on a slider in a hard disk drive (HDD) affects the HDD’s reliability. With the introduction of the thermal flying-height control (TFC) slider, the temperature in the head-disk interface (HDI) becomes non-uniform, which induces a temperature-gradient dependent force on particles moving in the HDI. This paper investigates the effect of this force, the so called thermophoretic force, on a particle’s motion in the HDI as well as its effect on particle contamination on the TFC slider. By numerical simulation of the particle’s trajectory together with an analytical analysis, we show that the thermophoretic force is always negligible compared to the Saffman lift force, which points to a direction parallel to the thermophoretic force. We conclude that the current particle contamination simulator without any thermophoretic forces included would not be significantly altered by the inclusion of these forces.

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