Solid Lubricant Coatings for Head-Disc Interface Wear
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Solution Overview
Problem
Current hard disc drives face limitations in data density and reliability due to the fly height of electromagnetic transducers, which can lead to head-disc contact and wear issues, especially with the use of liquid lubricants that fail at high temperatures and have high wear rates when solid lubricants are used.
Innovation Solution
A data storage apparatus with a storage medium coated in a first solid lubricant and a head separated by an air film, where the head's air bearing surface is coated with a second solid lubricant, such as sputtered polytetrafluoroethylene (PTFE), to reduce wear rates and maintain stability across a wide temperature range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If liquid lubricants are used to reduce friction and wear, then wear protection is improved, but reliability deteriorates due to stiction, spin-off and lubricant transfer
Solution Approach 1:
The patent changes the physical state of the lubricant from liquid to solid. Solid lubricants eliminate the problems of stiction, spin-off, and transfer that plague liquid lubricants, while still providing wear protection through their low shear strength and ability to form protective films on the head and disc surfaces.
Solution Approach 2:
The patent employs solid lubricant layers that can be replenished through normal drive operations. When worn, the solid lubricant on the head can be transferred back to the disc surface or replenished from a reservoir, providing a self-healing mechanism that maintains reliability over extended periods.
2Productivity
If head fly height is reduced to achieve higher data density, then productivity is improved, but reliability deteriorates due to increased possibility of head-media contact
Solution Approach 1:
The patent changes the tribological properties of the head-media interface by introducing solid lubricant coatings on both the head and disc surfaces. This allows the head to fly at ultra-low heights (below 10 nm) without suffering from increased wear or contact damage, as the solid lubricant layers protect both surfaces from mechanical degradation during contact events.
3Reliability
If solid lubricants are used to eliminate stiction and spin-off, then reliability is improved, but wear rate increases due to permanent removal of lubricant from original position
Solution Approach 1:
The patent divides the lubrication system into two separate solid lubricant layers: one on the head surface and one on the disc surface. This segmentation allows each layer to perform its protective function independently, and when one layer is worn or transferred, the other remains intact to continue providing protection, thereby reducing overall wear rate while maintaining reliability.
4Strength
If liquid lubricants are used for wear protection, then friction reduction is improved, but temperature resistance deteriorates as lubricants cannot survive HAMR temperatures of 400°C or above
Solution Approach 1:
The patent changes the material composition from organic liquid lubricants to inorganic or highly stable solid lubricant materials such as sputtered PTFE, silicon oxide, or diamond-like carbon. These materials maintain their structural integrity and lubricating properties at temperatures of 400°C and above, enabling their use in HAMR systems where liquid lubricants would decompose or evaporate.
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
The solution significantly reduces wear rates and maintains the head-media interface integrity, as demonstrated by successful 10 K-cycle contact start/stop tests without head crashes or severe contamination, indicating improved reliability and longevity.
Implementation Method 1
a head separated from the storage medium by an air film
Implementation Method 2
at least a portion of the air bearing surface is coated with a layer of a second solid lubricant
Data Source
AI summary
An apparatus comprises a storage medium having a surface coated with a layer of a first solid lubricant, and a head separated from the storage medium by an air film, the head having an air bearing surface, wherein at least a portion of the air bearing surface is coated with a layer of a second solid lubricant.