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Motivation For Gram
Load Adjust |
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Increasing
Magnetic Recording Density
requires lower
and
tighter
flying height distribution. |
| - |
Suspension
Preload is a significant
contributor to the flying
height. Even
more important for femto
sliders. |
| - |
HGA
(Head Gimble Assembly) and
HSA (Head Stack Assembly)
processes can produce significant
shift of the mean and sigma
of gram load and flying
height. |
| - |
Gram
load adjust can be used
to compensate for the deviations
caused by crown,camber,
etch depths, PSA, stacking
tolerances etc. on the flying
heights. |
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Strategy
For Gram Load Adjust
|
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Carry
out one time factory adjustment
to ensure
magnetic performance and
HDI reliability |
| |
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How
does the Gram Load Adjust
Work? |
|
|
1. |
Spring
Action of the hinge region
provides the suspension
preloaded. |
2. |
The
loadbeam transmits this
force to the slider. |
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Gram
Load Decrease |
|
 |
| Stress
in the hinge region can
be decreased by heating
at high enough temperature
for long enough time with
CW or quasi CW radiation. |
- |
Laser
heating is localized: No
harm to the read write element. |
- |
Faster
at higher temperatures but
with some risk of oxidation. |
|
Suspension
should be in "loaded"
state. |
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Gram
Load Increase I
|
| |
|
1. |
The
hinge area is treated with
short pulse length high
pulse energy radiation.
The surface layer melts. |
2. |
The underlying layers are
still"cold" in
this state. |
3. |
The intermediate layers
are plastically deformable. |
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Gram
Load Increase I
|
| |
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Contraction
of surface layer associated
with rapid refreezing produces
increased bending at the
hinge. |
|
a.
|
The
Gram load increases if the
melting is on the same side
of the hinge as the slider.
|
| |
b. |
The
suspension doesn't need
to be in the loaded state! |
| |
c. |
Melting
and refreezing of surface
cracks produces additional
stiffness. Important at
very short pulse lengths. |
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