SpinPoint Barracuda Series, Product Manual

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Barracuda Product Manual Rev04
33
5.1.3 Disk Stack Assembly
The disk stack assembly in the Barracuda hard disk drive consists of 1 or 2 disks and its respective spacers
secured on the hub of the spindle motor assembly by a disk clamp. It can contain two or four recording heads.
The aluminum-alloy disks are plated with a Ni-P for corrosion resistance reason. The magnetic films are
sputtered with different films of magnetic alloys. On the adjacent surface the manufacturers apply a thin film
of carbon to prevent damage resulting in data loss. To minimize wear, the media are also dipped with
lubricant and anti-wetting agent.
The data band is never touched by the recording heads or any component of the HDD. A dedicated zone
serves as runway for the flying recording sliders during power up and power down. Once approaching a
critical speed the heads are flying over the media. Until the powering up sequence is completed the actuator
with heads flying over are then permitted to move to data zone.
5.1.4 Head Stack Assembly
The head stack assembly consists of recording head or heads stacked on an assembly consisting of an
aluminum block and coil assembly. The voice coil which energizes a magnetic force with two magnets is
pivoted around a ball bearing. The E-block/coil sub-assembly is an integral part of a machined block with an
over-molded coil. Sliders containing read/write transducers are suspended on a stainless steel flexure(s) that
are secured through a unique swaging process onto the E-block arms.
The flexible circuit transmits electrical signal during read or write connects the read/write heads with the
PCBA via a connector through the base casting. Since the signals are very low in amplitude it gets amplified
as close to the transducer with a first stage amplifier (Preamp) on circuit.
5.1.5 Voice Coil Motor and Actuator Latch Assemblies
The rotary voice coil motor consists of upper and lower permanent magnets and magnetic yokes fixed to the
base casting and a rotary over-molded coil on the head stack assembly. Each magnet consists of two
alternating poles and is attached to the magnet yoke. Rubber crash stops mounted on the over-molded coil
and a magnetic yoke physically prevent the head(s) from moving beyond the designed inner boundary into
the spindle or off the disk surface.
Accessing of the actuator between OD-ID-OD positions on the disk is accomplished by applying coil current
surge from - to + then - which results in a magnetic force allowing a push-pull motion during actuation
process.
5.1.6 Air Filtration System
Heads fly at a fraction of a millionth of an inch above the disk surface. Therefore, it is of utmost importance
that the disk enclosures are not opened by unauthorized person or allowing air leakage through defective
filter, seal etc. Seagate HDAs are prepared in the state of the art super clean room environment with all parts
super-cleaned. To sustain this stringent clean air environment, the Barracuda is equipped with a high
efficiency re-circulating filter which is located in the path of the airflow close to the rotating disk and is
designed to trap any particles that might exist inside HDA.