Patent Application
20140231385
The present invention relates to magnetic data recording and more particularly a method for manufacturing a magnetic media having an ultra-thin lubrication layer for reduced magnetic spacing.
A key component of a computer is an assembly that is referred to as a magnetic disk drive. The magnetic disk drive includes a rotating magnetic disk, write and read heads that are suspended by a suspension arm adjacent to a surface of the rotating magnetic disk and an actuator that swings the suspension arm to place the read and write heads over selected circular tracks on the rotating disk. The read and write heads are directly located on a slider that has an air bearing surface (ABS). When the slider rides on the air bearing, the write and read heads are employed for writing magnetic impressions to and reading magnetic impressions from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
One parameter that greatly affects the performance of the magnetic recording system is the magnetic spacing between the read and write heads and the magnetic recording layer of the media. The strength of the magnetic signal decreases exponentially with increasing magnetic spacing. However, in order for the magnetic data storage system to operate reliably, certain non-magnetic layers must be provided over the magnetic recording layer of the magnetic medium. Such layers can include a protective overcoat layer, and a lubrication layer. Although these layers are necessary to the reliable operation of the system, their presence actually decreases the performance of the system by increasing magnetic spacing.
The present invention provides a method for manufacturing a magnetic media for data recording. The method includes, constructing a magnetic disk, and depositing a lubricant layer on the magnetic disk, the lubricant layer comprising two different lubricant materials. The magnetic disk is exposed to a solvent vapor to remove one of the lubricant materials, leaving a layer of the second lubricant material that has a thickness of less than 1 nanometer.
The present invention can also provide a magnetic media for magnetic data recording that includes a magnetic disk having a lubricant layer formed thereon, the lubricant layer having a thickness less than one nanometer. The lubricant layer can be formed by a method that includes constructing a magnetic disk; depositing a lubricant layer on the magnetic disk, the lubricant layer comprising two different lubricant materials; and exposing the magnetic disk to a solvent vapor to remove one of the lubricant materials, leaving a layer of the second lubricant material that has a thickness of less than 1 nanometer.
The lubricant layer consists entirely or almost entirely of a bonded lubricant material having a thickness less than one nanometer. The lubricant layer can be as thin as a single molecular mono-layer.
The lubricant layer can be deposited by a process that advantageously allows the disk to have a thicker lubricant layer during burnishing, which ensures that the burnishing process can be effectively carried out without any damage to the disk. Then, after burnishing, the majority of the lubricant layer is removed by exposure to solvent vapor, leaving a very thin layer bonded lubricant.
These and other features and advantages of the invention will be apparent upon reading of the following detailed description of preferred embodiments taken in conjunction with the Figures in which like reference numerals indicate like elements throughout.
For a fuller understanding of the nature and advantages of this invention, as well as the preferred mode of use, reference should be made to the following detailed description read in conjunction with the accompanying drawings which are not to scale.
The following description is of the best embodiments presently contemplated for carrying out this invention. This description is made for the purpose of illustrating the general principles of this invention and is not meant to limit the inventive concepts claimed herein.
Referring now to
At least one slider 113 is positioned near the magnetic disk 112, each slider 113 supporting one or more magnetic head assemblies 121. As the magnetic disk rotates, slider 113 moves radially in and out over the disk surface 122 so that the magnetic head assembly 121 can access different tracks of the magnetic disk where desired data are written. Each slider 113 is attached to an actuator arm 119 by way of a suspension 115. The suspension 115 provides a slight spring force which biases slider 113 against the disk surface 122. Each actuator arm 119 is attached to an actuator means 127. The actuator means 127 as shown in
During operation of the disk storage system, the rotation of the magnetic disk 112 generates an air bearing between the slider 113 and the disk surface 122 which exerts an upward force or lift on the slider. The air bearing thus counter-balances the slight spring force of suspension 115 and supports slider 113 off and slightly above the disk surface by a small, substantially constant spacing during normal operation.
The various components of the disk storage system are controlled in operation by control signals generated by control unit 129, such as access control signals and internal clock signals. Typically, the control unit 129 comprises logic control circuits, storage means and a microprocessor. The control unit 129 generates control signals to control various system operations such as drive motor control signals on line 123 and head position and seek control signals on line 128. The control signals on line 128 provide the desired current profiles to optimally move and position slider 113 to the desired data track on disk 112. Write and read signals are communicated to and from write and read heads 121 by way of recording channel 125.
As discussed above, the magnetic disk 112 must include various layers formed over the magnetic layer in order to ensure reliable operation of the disk drive system. However, the presence of these layers such as a protective overcoat and a lubrication layer increase the magnetic spacing, which decreases the performance of the system. The present invention mitigates this problem by minimizing the thickness of the thickness of the lubrication layer. The lubrication layer constructed by the present invention can be a thin as a molecular mono-layer.
In order to construct a magnetic media, a magnetic disk substrate 202 is placed in a deposition tool, such as a sputter deposition tool. Various layers of the magnetic media 112, such as the magnetic recording layer 204 are deposited onto the wafer. It should be pointed out that various other layers, not specifically disclosed here could also be deposited and included in the finished disk, such as but not limited to a soft magnetic under-layer, one or more seed layers, etc. In addition, the magnetic media 112 can be formed as a bit patterned media wherein the magnetic recording layer 206 is actually formed as discrete islands or discrete data tracks separated by non-magnetic spaces or non-magnetic material.
After the protective overcoat 206 has been applied, a lubricant material is applied. The lubricant is a combination of two lubricant materials, one that is a bonded lubricant and one that is a non-bonded lubricant. More specifically the lubricant can include a first lubricant that is a functional perfluoropolyether (e.g. ZTMD®) and a second lubricant that is a non-functional perfluoropolyether (e.g. Z15®). The two types of lubricant can be applied by dipping the disk in a bath or could be applied by vapor deposition, although dipping is preferred because it provides better uniformity. Also, the two different lubricants can be mixed and applied at once which saves time and space, or can be applied sequentially.
The deposition of the layers 204, 206 and other layers not shown, inevitably results in certain asperities or a certain amount of roughness that must be addressed in order for the magnetic media to function in a magnetic disk drive. In order to remove these asperities and to provide a sufficiently smooth media surface a burnishing process must be performed. The burnishing process involves spinning the disk while moving a burnishing pad over the surface of the disk. Any asperities or surface roughness will be worn off by the burnishing pad. This pad burnishing is an essential step in manufacturing the magnetic media 112. Poor burnishing results in overcoat scratches and production of solid particles, which lead to poor corrosion-resistance and low glide yield. A certain minimum amount of lubricant is demanded by the burnish process to minimize damage to the disk. The burnish-required lubricant thickness, which can be greater than 1 nm will soon exceed that in the head magnetic spacing (HMS) budget.
To satisfy both requirements (low fly height, and sufficient lubricant thickness during burnish) the lubricant thickness can be reduced after the pad burnish process. The issue is how to reduce the lubricant thickness in a uniform manner to within 0.05 nm) or 0.5 Angstroms). A simple solvent squirting or immersing cannot achieve this. Such a process leads to dripping marks and lubricant lines and generally uneven lubricant application. A solution to these problems is described herein.
The burnishing process requires a significantly thicker lubricant than is needed in the finished disk drive system. The above described dip coating of a dual material lubricant provides a lubricant having a thickness of 12-18 Angstroms that is more than sufficient to ensure good burnishing characteristics with little or no scratching or solid particle production.
After burnishing has been completed, a majority of the lubricant can be removed by a process that evenly removes all of the lubricant except for a portion of the lubricant that has been bonded to the under-layer 206. The process uses solvent vapor to reduce the media lubricant thickness to a sub-nanometer value after burnishing at a higher lubricant thickness. The final sub-nanometer thickness is determined by the bonded fraction. The bonded fraction remains on the disk surface. Thus, the lubricant remaining on the disk is 100% bonded after de-lubing. However, the final lubricant bonding will decrease to a thermally equilibriated bonded fraction at the drive operational temperature. With reference to
Two stages of cooling prevent the solvent from escaping. This two stage cooling can be provided by a first stage of cooling coils 312 and a second stage of cooling coils 314. The solvent, which can be for example HFE-7100® or Vertrel XF®, has a much lower boiling point (e.g. 50-60 degrees C.) than the lubricant, which can be formed of long-chain perfluoropolyether polymers, such as A20H, Z-dol®, Z-Tetraol®, or ZTMD®. The above process, which uses a mixture of bonded and non-bonded lubricants and subsequent lubrication removal by solvent vapor results in an extremely thin lubrication layer of less than 1 nm. The thickness of the lubrication layer is preferably a molecular mono-layer as described above with regard to
While various embodiments have been described above, it should be understood that they have been presented by way of example only and not limitation. Other embodiments falling within the scope of the invention may also become apparent to those skilled in the art. Thus, the breadth and scope of the invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
This application is a divisional of U.S. patent application Ser. No. 13/316,328 filed Dec. 9, 2011, which is herein incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13316328 | Dec 2011 | US |
| Child | 14266709 | US |
