A Heat Transfer Study in the Head Disk Interface and an Insight to Heat Assisted Magnetic Recording Design

2017 ◽  
Author(s):  
Haoyu Wu ◽  
David Bogy
Keyword(s):  
Heat Transfer ◽  
Magnetic Recording ◽  
Convective Heat Transfer Coefficient ◽  
Head Disk Interface ◽  
Heat Assisted Magnetic Recording ◽  
Disk Interface ◽  
Height Control ◽  
Contact Sensor ◽  
Series Of Experiments ◽  
Fly Height

Understanding the heat transfer in the head disk interface (HDI) in the heat assisted magnetic recording (HAMR) is important. In this paper, we report on a series of experiments to study the heat transfer in the HDI using the perpendicular magnetic recording (PMR) heads and media. The temperature increase of the embedded contact sensor (ECS) and the thermal fly-height control (TFC) heater was compared in the fly setup and non-fly setup. A series of simulations were performed to explain the results. We show that the design of the air bearing surface can significantly affect the pressure distribution in the read/write transducer area, and thereby affect the convective heat transfer coefficient.

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.

Experimental Study of Nanoscale Head-Disk Heat Transfer In Heat-Assisted Magnetic Recording

2021 ◽  
Author(s):  
Qilong Cheng ◽  
David B. Bogy
Keyword(s):  
Heat Transfer ◽  
Silicon Wafer ◽  
Magnetic Recording ◽  
Laser Exposure ◽  
Heat Assisted Magnetic Recording ◽  
Contact Sensor ◽  
Higher Temperature ◽  
Dc Current ◽  
Fly Height ◽  
Head Temperature

Abstract To study the nanoscale heat transfer and laser-related protrusions in heat-assisted magnetic recording (HAMR), we performed static touchdown experiments between HAMR waveguide heads and non-rotating media such as a silicon wafer and a recording disk with an AlMg substrate. During the static touchdown, the laser element is energized with DC current and the embedded contact sensor (ECS) is used to monitor the head temperature. The experimental results show that the thermal fly-height control (TFC) touchdown power decreases with increasing laser current. Meanwhile, the head temperature increases due to the laser heating. From this the ECS resistance rise induced by the laser is extracted. The results show that the silicon wafer dissipates heat effectively under the laser exposure, while the AlMg-substrate disk undergoes a higher temperature rise, which in turn heats the head.

A Numerical Study of the Nanoscale Heat Transfer in the Head-Disk Interface for Heat Assisted Magnetic Recording

2016 ◽  
Author(s):  
Haoyu Wu ◽  
David Bogy
Keyword(s):  
Heat Transfer ◽  
Magnetic Recording ◽  
Transfer Problem ◽  
Numerical Study ◽  
Near Field ◽  
Experimental Result ◽  
Head Disk Interface ◽  
Heat Assisted Magnetic Recording ◽  
Disk Interface ◽  
Nanoscale Heat Transfer

The near field transducer (NFT) overheating problem is an issue the hard disk drive (HDD) industry has faced since heat-assisted magnetic recording (HAMR) technology was first introduced. In this paper, a numerical study of the head disk interface (HDI) is performed to predict the significance of the nanoscale heat transfer due to the back heating from the disk. A steady-state heat transfer problem is first solved to get the disk temperature profile. Then an iterative simulation of the entire HDI system is performed. It shows that the heat transfer coefficient in the HDI increases to about 6:49 × 106 W/(m2K) when the clearance is 0:83 nm. It also shows that in the free space laser scenario, the simulation result is close to the experimental result.

Nanoscale heat transfer in the head-disk interface for heat assisted magnetic recording

2016 ◽  
Vol 108 (9) ◽  
pp. 093106 ◽  
Author(s):  
Haoyu Wu ◽  
Shaomin Xiong ◽  
Sripathi Canchi ◽  
Erhard Schreck ◽  
David Bogy
Keyword(s):  
Heat Transfer ◽  
Magnetic Recording ◽  
Head Disk Interface ◽  
Heat Assisted Magnetic Recording ◽  
Disk Interface ◽  
Nanoscale Heat Transfer

Head–Disk Interface Materials Issues in Heat-Assisted Magnetic Recording

2014 ◽  
Vol 50 (3) ◽  
pp. 137-143 ◽  
Author(s):  
Bruno Marchon ◽  
Xing-Cai Guo ◽  
Bala Krishna Pathem ◽  
Franck Rose ◽  
Qing Dai ◽  
...  
Keyword(s):  
Magnetic Recording ◽  
Head Disk Interface ◽  
Heat Assisted Magnetic Recording ◽  
Disk Interface ◽  
Interface Materials

scholarly journals Parametric Investigations at the Head-Disk Interface of Thermal Fly-Height Control Sliders in Contact

2012 ◽  
Vol 2012 ◽  
pp. 1-11 ◽  
Author(s):  
Sripathi V. Canchi ◽  
David B. Bogy ◽  
Run-Han Wang ◽  
Aravind N. Murthy
Keyword(s):  
Hard Disk Drives ◽  
Air Bearing ◽  
Head Disk Interface ◽  
Bearing Surface ◽  
Surface Design ◽  
Disk Interface ◽  
Height Control ◽  
Experimental Findings ◽  
And Control ◽  
Fly Height

Accurate touchdown power detection is a prerequisite for read-write head-to-disk spacing calibration and control in current hard disk drives, which use the thermal fly-height control slider technology. The slider air bearing surface and head gimbal assembly design have a significant influence on the touchdown behavior, and this paper reports experimental findings to help understand the touchdown process. The dominant modes/frequencies of excitation at touchdown can be significantly different leading to very different touchdown signatures. The pressure under the slider at touchdown and hence the thermal fly-height control efficiency as well as the propensity for lubricant pickup show correlation with touchdown behavior which may be used as metrics for designing sliders with good touchdown behavior. Experiments are devised to measure friction at the head-disk interface of a thermal fly-height control slider actuated into contact. Parametric investigations on the effect of disk roughness, disk lubricant parameters, and air bearing surface design on the friction at the head-disk interface and slider burnishing/wear are conducted and reported.

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