Perfluorinated Polyether Lubricants for Hard Disk Drive Reliability
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Solution Overview
Problem
In hard disk drive applications, the reduction of flying height to increase disk drive capacity leads to severe slider/lubricant interactions, causing moguls, ripples, and lubricant depletion on the disk surface, resulting in errors and potential damage.
Innovation Solution
The use of derivatives of perfluoropolyether lubricants with branched perfluoropolyalkyl ether segments and surface-active end groups, such as trifluoromethyl and perfluoroethyl ether units, which form a low surface energy layer on the magnetic media, reducing interactions and enhancing durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the flying height of the slider above the disk is reduced to increase disk drive capacity, then the storage capacity is improved, but severe slider/lubricant interactions occur causing moguls, ripples, and lubricant depletion
Solution Approach 1:
The patent changes the chemical composition parameters of the lubricant by using perfluoropolyether derivatives with specific molecular structures (containing perfluorobutyl ether units, perfluoroethyl ether units, and anchor groups) to achieve lower surface energy and reduced slider-lubricant interactions, thereby maintaining reliability at reduced flying heights
Solution Approach 2:
The lubricant is designed as a composite molecular structure combining multiple functional segments: perfluoropolyalkyl ether segments for low surface energy, anchor groups for surface attachment, and trifluoromethyl groups for enhanced durability. This composite structure resolves the contradiction by providing both low interaction and stable lubrication
2Ease of operation
If conventional lubricants are used at lower flying heights, then the disk drive can operate, but lubricant gathers on the slider forming drops that fall onto the disk surface leaving thick regions
Solution Approach 1:
The lubricant's surface energy parameters are modified through the use of perfluorinated segments, which have inherently lower surface energy than conventional hydrocarbon lubricants. This parameter change prevents lubricant accumulation and maintains uniform distribution even at reduced flying heights
Solution Approach 2:
The low surface energy property, which could be seen as reducing lubrication effectiveness, is actually converted into a benefit by preventing excessive lubricant adhesion to the slider. The lubricant maintains sufficient coverage without forming damaging drops, turning a potential disadvantage into a solution for uniform distribution
3Quantity of substance
If thicker regions, moguls, and ripples are present on the disk surface, then lubricant coverage is maintained, but errors in reading the disk occur
Solution Approach 1:
The molecular weight and chain structure parameters of the lubricant are optimized to achieve the right balance: high enough to provide adequate coverage and protection, but low enough to prevent excessive buildup. The perfluoropolyether structure with controlled chain length ensures proper lubricant film formation without creating reading errors
4Measurement precision
If regions without lubricant are present on the disk surface, then reading errors are reduced, but surface scratching in the disk or damage to the head occurs
Solution Approach 1:
The chemical composition parameters are changed to create a lubricant with optimal adhesion and cohesion properties. The anchor groups ensure strong attachment to the disk surface preventing depletion, while the perfluorinated chains provide low friction and wear protection, maintaining both reading accuracy and surface integrity
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 lubricant significantly reduces errors and damage by maintaining a stable lubricant layer, improving clearance control and durability, and extending the time to head failure during touchdown stress tests.
Implementation Method 1
Boundary lubricants form a lubricating film when functional groups of the lubricant attach to the surface being lubricated
Implementation Method 2
The lubricant includes segments of branched perfluoropolyalkyl ether... the surface agent includes at least one trifluoromethyl perfluoropolyalkyl ether segment including perfluorobutyl ether units
Data Source
AI summary
A surface agent includes two end portions and a middle portion disposed between the end portions. The end portions include an anchor group or a truncation group. The anchor group includes at least one surface active functional group. The midsection includes at least one perfluoroalkyl-branched perfluorinated ether unit.