Electric heating – Metal heating – By arc
Reexamination Certificate
2002-04-08
2003-09-09
Dunn, Tom (Department: 1725)
Electric heating
Metal heating
By arc
Reexamination Certificate
active
06617542
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of treating surfaces on a magnetic head disk drive suspension, and in particular, to laser treating operative surfaces of head lift pads and load point dimples on a head suspension.
BACKGROUND OF THE INVENTION
In a dynamic rigid disk storage device, a rotating disk is employed to store information. Rigid disk storage devices typically include a frame to provide attachment points and orientation for other components, and a spindle motor mounted to the frame for rotating the disk. A read/write head is formed on a “head slider” for writing and reading data to and from the disk surface. The head slider is supported and properly oriented in relationship to the disk by a head suspension that provides both the force and compliance necessary for proper head slider operation. As the disk in the storage device rotates beneath the head slider and head suspension, the air above the disk also rotates, thus creating an air bearing which acts with an aerodynamic design of the head slider to create a lift force on the head slider. The lift force is counteracted by a spring force of the head suspension, thus positioning the head slider at a desired height and alignment above the disk that is referred to as the “fly height.”
Typically, the magnetic head is about 0.02 microns away from the disk while the disk is moving. In most disk 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 disk surfaces.
FIG. 1
shows a typical 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 must rub against the ramp
8
. The ramp structure
10
is typically 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.
In addition to lift tabs, certain types of head suspensions include a generally spherical dimple having a convex surface formed in either the load beam or the cantilever region of the flexure, such as disclosed in U.S. Pat. No. 6,078,470 (Danielson et al.).
FIGS. 2 and 3
illustrate a head suspension assembly comprising a head suspension
61
with a load point dimple and a head slider
69
. The head suspension
61
includes a load beam
62
and a flexure
64
on a distal end of load beam
62
. Load beam
62
is generally comprised of a mounting region
63
on a proximal end of load beam
62
, a rigid region
68
, and a spring region
67
between mounting region
63
and rigid region
68
.
Mounting region
63
further includes base plate
63
a
, secured to load beam
62
by conventional means such as spot welds, and mounting structure
63
b
for mounting head suspension
61
to a rotary actuator of a rigid disk drive (see FIG.
1
). Mounting structure
63
b
enables head suspension
61
to be positioned over an associated disk so the head can read data from or write data to the disk during the normal operation of the disk drive. Spring region
67
generally includes a bend or radius to provide a spring force used to counteract the aerodynamic lift force acting on flexure
64
in use. Rigid region
68
transfers the spring force from spring region
67
to a load region
68
a
at the distal end of load beam
62
. Load region
68
a
then transfers the spring force to flexure
64
.
Flexure
64
includes a cantilever region
65
having a slider mounting surface to which a head slider
69
is mounted. A free end
65
a
of the cantilever region is movable vertically in response to pitch and roll movements of the head slider
69
and cantilever region
65
. Flexure
64
further includes arms
65
b
and
65
c
that extend longitudinally from a proximal end of flexure
64
to a cross piece
65
d
on a distal end of flexure
64
. Offset bends
66
a
and
66
b
are located in cross piece
65
d
of flexure
64
to provide a planar mounting region for head slider
69
and an offset between cantilever region
65
and arms
65
b
and
65
c.
Dimple
66
is formed in cantilever region
65
of flexure
64
, and dimple
66
confronts load region
68
a
of load beam
62
. Dimple
66
provides a specific manner by which the spring force of spring region
67
is transferred from load region
68
a
of load beam
62
to cantilever region
65
of flexure
64
, and furthermore, permits pitch and roll movements of the cantilever region
65
and head slider
69
as described in greater detail below. The dimple
66
acts as a “load point” between the flexure/head slider and the load beam, and dimples designed to serve this purpose are referred to as “load point dimples”.
A load point dimple provides clearance between the flexure and the load beam, and serves as a point about which the head slider can gimbal in response to the aerodynamic forces generated by the air bearing. Variations in the rotating disk create fluctuations in these aerodynamic forces. The aerodynamic forces cause the head slider to roll about a longitudinal axis of the head suspension, and to pitch about an axis planar with the head suspension but perpendicular to the longitudinal axis. The load point dimple serves as the pivot point about which the flexure and head slider gimbal in response to the pitch and roll aerodynamic forces.
Lift tabs and load point dimples that are stamped or coined from sheet metal have a number of limitations. The extreme pressure used to stamp the parts causes the die surface to degenerate through metal transfer. The area of highest pressure can become rougher than it was before the stamping or coining operation. Because of the nature of the coining process, the highest pressure is typically at the apex of the feature, which is typically the operative surface. Features smoothed by the coining process still produce debris when rubbed, such as against a ramp or a tang in a gimbal assembly, causing particulate contamination inside the disk drive a
Christianson Mark R.
Hayen Fredrick V.
Kinkaid Nathan M.
Koba Hryhory T.
Faegre & Benson LLP
Hutchinson Technology Inc.
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