Hardware Reference
In-Depth Information
Figure 1.6: Read/Write head slider on disk
low pitch and roll stiffness. The load beam is made relatively thicker compared
to the
fl
exure to provide high stiffness in the other directions that are required
for the servo. The
fl
exure is laser welded to the load beam. The edges of
the load beam are often bent to form a rail and, therefore a half-I beam, to
increase its stiffness (Figure 1.6). The load beam ends at the base of the
suspension, which is a relatively thick rectangular piece. The base provides
a mechanism to swage it to the end of the actuator arm. The edge of the
load beam is removed at the end near the base plate so that there is room for
up-and-down motion of the suspension arm. This vertical movement of the
suspension is necessary to accommodate unevenness of the disk surface and
wobbling of disk. Whenever the slider encounters a slowly increasing bump on
the disk surface, the aerodynamic force pushes the slider away from the disk.
The narrow scope of vertical movement of the suspension accommodates these
motions.
More recent tracking issues come from the increase in disk rotational speeds.
The turbulent nature of the air between the disk and actuator causes additional
off track motion at the head. Once again, a suspension with higher stiffness
works better to reduce the response to this windage energy. In addition, low
pro
fi
le designs extract less energy from the turbulent air.
Like the other components of the HDD, the sliders have gone through
evolution. The dimension of the slider of the Winchester drive introduced in
the 1960's was 5.6mm × 4mm × 1.93mm.ThisisalsoknownastheFul l -s i ze
slider. The next generation sliders, known as 100% minislider , were introduced
in 1975 and had the dimensions of 4mm×3mm×0.8mm. Both of these sliders
were made of ferrite. This was followed by the 70% micro slider (2.84mm ×
2.23mm×0.61mm) in 1987, the 50% nano slider (2.05mm×1.6mm×0.43mm)
in 1990, and the 30% pico slider (1.25mm× 1.0mm× 0.3mm) in 1995. These
three classes of sliders are made of Al
2
O
3
−TiC. The air-bearing features of
the sliders were machine railed for full-size, mini slider and micro sliders, and
etched railed for nano slider and pico slider. The industry is currently preparing
for a transition to the 20% femto slider (0.85mm × 0.7mm× 0.23mm).
