Dynamic magnetic information storage or retrieval – Head mounting – Disk record
Reexamination Certificate
1999-04-16
2001-09-11
Heinz, A. J. (Department: 2754)
Dynamic magnetic information storage or retrieval
Head mounting
Disk record
C360S255000, C360S255500, C360S255900
Reexamination Certificate
active
06288876
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for smoothing load/unload lift tabs, and to load/unload lift tabs smoothed by the method. The lift tab of a head gimbal assembly functions to interact with a load/unload ramp to lift read/write heads from the disk surface.
BACKGROUND OF THE INVENTION
Computer hard drives typically employ a number of rapidly rotating disks having a coating of magnetic data storage material. Each disk is matched with a magnetic read/write head that is held very close to the disk surface. The magnetic read/write head can read and write data on the magnetic disk as it moves.
Some hard drives have disks with nonstick portions that will not cause damage to the magnetic heads if the heads rest on the nonstick portion for an extended period of time. Such hard drives are known as contact start/stop (CSS) hard drives. A CSS hard drive does not require a lift tab or load/unload ramp.
The magnetic head is prevented from contacting the disk surface by a cushion of air moving with the disk. Typically, the magnetic head is about 0.02 microns away from the disk while the disk is moving.
The need for very small spacing between the head and disk during the operation of the drive requires that the head and disk surfaces be very smooth. In non-CSS hard drives it is important for the magnetic head and disk surface not to come in contact when the disks are not rotating (i.e., when the hard drive is not powered). If a disk and magnetic head are at rest and in contact for a period of time, the head and disk surface can stick together, resulting in damage to the disk surface when the disks start to rotate. In some cases the stiction force can prevent the disks from rotating altogether. Also, the disk must start from rest, and a certain minimum velocity is required for the magnetic head to float over the disk surface. Therefore, each startup of the hard drive can result in the magnetic head and disk surface rubbing for a distance until the disk achieves sufficient speed to form the air cushion.
For these reasons, load/unload ramp structures have been used in some hard drives to hold the magnetic heads away from the disk surfaces while the hard drive is not operating. The magnetic heads are released from the ramp structure when the disks have achieved the minimum speed for causing the magnetic heads to float above the disk surfaces. CSS hard drives do not have load/unload ramp structures or lift tabs.
FIG. 1
(prior art) shows a typical prior art load/unload type hard drive with three disks
2
. An actuator arm
3
supports a suspension
4
, a slider
5
and a lift tab
6
. A magnetic read/write head (not shown) is located on a bottom surface of the slider
5
. The suspension
4
and slider
5
together comprise a head gimbal assembly. The actuator arm
3
pivots about a pivot post
9
. The lift tab
6
is positioned on the suspension
4
so that it engages a ramp
8
on a ramp structure
10
. The ramp
8
imparts an upward force on the lift tab
6
which lifts the slider
5
and magnetic head away from the disk
2
. The magnetic head is thereby not in contact with the disk
2
whenever the lift tab
6
is moved onto the ramp
8
. In order for the lift tab
6
to lift the slider from the disk, the lift tab
6
must rub against the ramp
8
.
Although not shown in
FIG. 1
, the hard drive has additional arms, suspensions and sliders so that there is at least one suspension and slider for each disk surface.
FIG. 2
(prior art) shows a closeup side view of a lift tab
6
engaging the ramp
8
. Shown are three different positions for the lift tab
6
. A rounded bottom surface
12
of the lift tab
6
must rub against the ramp
8
in order for the slider to be lifted from the disk
2
. The slider
5
is unloaded from the disk as the lift tab moves from left to right, and loaded onto the disk
2
as the lift tab moves from right to left.
Typically, the ramp structure
10
is made from low-friction polymer materials. Low friction ramps
8
reduce the amount of energy required to unload the magnetic heads (a concern during unpowered unloading).
Lift tabs are typically made of metal such as stainless steel. Since they are harder than the ramp structure (made of plastic), the lift tab may abrade the ramp during loading and unloading. Abrasion creates contaminate particles within the hard drive that can damage the sensitive slider/disk interface. It is therefore necessary for the bottom lift tab surface (which contacts the ramp) to be as smooth as possible. A smooth lift tab surface produces fewer particles when rubbed over the surface of the ramp.
Of particular concern are lift tabs stamped from sheet metal. This is because the process for making sheet metal, and the stamping process, produce relatively rough surfaces.
One method used in certain IBM products to smooth the lift tab is to press the lift tab against a very smooth and hard die. This ‘coining’ process smoothes the surface by closing cracks in the lift tab surface and planarizing protrusions. Smoothness is limited by the surface quality of the die and the pressure used. Lift tabs smoothed by the coining process still produce rather large numbers of particles when rubbed against a ramp.
There exists a need in the art for improved methods of smoothing the lift tab. Such a method would provide for reduced particulate contamination inside a data storage hard drive, leading to higher reliability.
OBJECTS AND ADVANTAGES OF THE INVENTION
Accordingly, it is a primary object of the present invention to provide a lift tab for head gimbal assemblies in a non-CSS hard drive that:
1) has a very smooth surface for contacting a ramp structure;
2) produces fewer particles when rubbed against a ramp structure compared to prior art lift tabs.
It is also a primary object of the present invention to provide a method for smoothing a lift tab for a non-CSS hard drive that:
1) produces very smooth lift tab surfaces;
2) is relatively inexpensive;
3) is scalable for volume production of smooth lift tabs;
4) is compatible with a wide variety of lift tab structures and shapes;
5) can be used on stainless steel lift tabs.
These and other objects and advantages will be apparent upon reading the following description and accompanying drawings.
SUMMARY OF THE INVENTION
These objects and advantages are attained by a method of smoothing a surface of a lift tab having surface roughness features of a characteristic depth (e.g. a peak to valley height or crack depth). The method includes the step of heating the lift tab surface with an energy pulse. The energy pulse has a power density (Megawatts/cm
2
) sufficient to cause melting of the lift tab surface. The energy pulse strikes the surface for a duration sufficient such that the lift tab surface is melted to a depth greater than the characteristic depth. Also, the surface is melted to a depth less than 10 microns. After the surface is melted, the surface is allowed to cool, forming a very smooth melted and refrozen spot. The energy pulse is preferably a laser beam. The laser beam can be from a Q-switched laser or the like. The energy pulse can also be from a CW (continuous wave) laser or other continuous energy source which is scanned across the lift tab surface. Also, other kinds of pulsed energy sources can be used.
Preferably, the energy pulse has a power density in the range of 50-150 megawatts/cm
2
. The energy pulse can strike the surface for a duration in the range of 10-500 nanoseconds, more preferably in the range of 150-250 nanoseconds. Preferably, the surface is melted to a depth in the range of 0.2 to 10 microns, more preferably in the range of 1.0 to 3.0 microns.
The present invention also includes lift tabs smoothed according to the method of the present invention.
The present invention further includes a lift tab having a curved surface for contacting a load/unload ramp, with an area of the curved surface smoothed by melting and refreezing. The melted and refrozen area may comprise several melted and refrozen spots. The melted and refrozen spots may be surrounded by ripples
Albrecht Thomas Robert
Kozlovsky William Joseph
Singh Gurinder Pal
Suk Mike
Heinz A. J.
International Business Machines - Corporation
Lumen Intellectual Property Services
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