Proximity Recording Head Technology
Quantum is using proximity recording heads in its new low cost desktop drives to meet the price and capacity demands of entry-level PCs.
The entry-level desktop PC market continues
to demand higher capacity and faster performance from hard disk
drives. With applications such as Internet file downloading, increased
file sizes with advanced 32-bit operating systems and multimedia
applications, demand for capacity is doubling every year. This
has pushed entry-level disk drive capacities to 1.0 gigabyte (GB)
and beyond moving into 1997. This strong demand for storage has
pushed hard disk suppliers to apply new technologies to meet this
These new technologies must meet the increasing
capacity requirements but do so economically. Disk drive suppliers
must continue to increase the areal densities, or number of data
bits per square inch, to meet this increasing demand for storage.
This challenge is being realized using both new head designs and
read channel technologies; however, the improvements in head designs
have been key to achieve these capacity increases.
Head Technology Development
To keep up with end-user demand for storage,
Quantum has utilized a diversified strategy of head technologies.
The use of inductive heads have increased disk drive areal densities
over the past several years using Thin Film and Metal in Gap (MiG)
technologies. In 1995, Quantum utilized these head designs in
delivering the Trailblazer 420/850 drives based on MiG heads and
the Fireball 640/1280 and Bigfoot 1.2/2.5 drives based on standard
thin-film heads. These inductive heads have offered low cost and
mature processing technology for Quantum in meeting the high volume
requirements for its drive programs.
Additionally, Quantum has also been the leader
in the development of magnetoresistive (MR) heads for desktop
PC disk drives with its introduction of the Sirocco and Fireball
TM disk drives. With separate read and write heads, the MR head
designs of these drives allow for higher areal densities than
drives with inductive heads. Quantum has recently announced the
next generation of MR head disk drives with the Fireball ST and
its first MR-based 5.25-inch Bigfoot CY.
To maintain Quantum's strength in offering
disk drives that also meet the demands of entry-level PC systems,
Quantum is leveraging from a new generation of inductive thin
film heads that use proximity recording technology. Quantum's
development of this technology over the past two years has enabled
the introduction of our latest value-class drive family, the Pioneer
Proximity Recording Primer
The primary benefit of using proximity recording
head technology is a lower flying height. The lower flying height
means less spacing loss between the head and disk interface, thus
improving the signal to noise ratio and allowing higher areal
densities while using a low-cost thin film head design.
History of Proximity Recording
The first generation of proximity recording
head technology was known as Tri-Pad. This head design enabled
areal densities of approximately 400 megabits (Mb) per square
inch which resulted in 540 megabytes (MB) per disk drive. Successive
designs have produced heads that can achieve 850 MB per disk.
The Tri-Pad head design and the "machined" process which
produces the head's air bearing design creates a variable flying
height profile across the disk diameter. The head flies lower
at the inner diameter (ID) of the disk and higher at the outer
diameter (OD). (See Figure 1)
Figure 1: Tri-Pad Flying Profile
This flying profile of the Tri-Pad head allows
for higher areal densities than standard thin film designs. However,
due to the variable flying profile, the signal strength across
the disk diameter is reduced, limiting its areal density. Thus,
the capacity per disk achievable with Tri-Pad heads appears to
be limited to approximately 850 MB.
Tri-NPAB Proximity Recording Heads
Proximity recording development efforts have
produced a second generation design known as Tri-NPAB (Negative
Pressure Air Bearing). This new design enables higher areal densities
by providing a relatively flat flying profile across the disk
surface. Using an advanced "ion-etched" process to shape
the head's air bearing, Tri-NPAB heads avoid the Tri-Pad effects
of higher flying heights at the outer diameter (OD) of the disk.
Thus, the "lift" at the OD of the disk is less than
that of earlier Tri-Pad designs, increasing the signal strength
and enabling higher drive capacities.
Further, the Tri-NPAB design allows the head
to fly lower across the entire disk (as low as 0.8 microinches).
This contributes to the Tri-NPAB's ability to offer approximately
25 percent greater areal density over previous generation proximity
recording heads. Thus, Tri-NPAB heads enable over 700 Mb per square
inch areal densities, resulting in drives with over 1 GB of storage
per disk! Quantum's Pioneer SG family of disk drives takes advantage
of the areal density improvements of Tri-NPAB heads to realize
a 1.0 GB (single platter) and 2.1 GB (dual platter) design.
As shown in Figure 2, texturing of the disk
surface results in a glide height on the disk. In order to produce
the necessary signal levels for the Tri-NPAB heads, the head must
fly at a "near-contact" level above the glide height
of the disk. This means that at various points across the disk
surface the Tri-NPAB head transducer will come in contact with
the glide height as shown by the Tri-NPAB dashed line.
Figure 2: Head Technology Flying Profile Comparisons
Tri-NPAB heads fly lower than other types of
heads. Standard thin film and MiG inductive heads fly higher but
also achieve less capacity. MR heads fly the highest but also
achieve the highest capacity due to their unique two element (read
& write) design.
Proximity Recording and Drive Reliability
As previously discussed, the Tri-NPAB head
design has the ability to fly at very low levels above the disk
surface enabling higher areal densities. Tri-NPAB designs utilize
a unique air bearing design through its "ion-etched"
production process to minimize the contact with the media glide
height. The design of the Tri-NPAB heads and their "near-contact"
nature allows for periodic contacts between the head and disk
interface without experiencing excessive wear to either the heads
or media. This is an important point since the reliability of
the head/media interface will continue to be stressed as flying
heights of all head technologies continue to decrease. The design
of Tri-NPAB heads account for this reliability concern while achieving
lower flying heights above the disk surface.
Extensive testing in the development of the
Quantum Pioneer SG drive has proven equivalent reliability of
the Tri-NPAB head technology with that of Quantum's "flying"
head drives. Used with all of its products, Quantum's unique Consolidated
Testing subjects drives to accelerated environmental conditions
including but not limited to temperature, humidity, altitude,
shock and vibration. Additional tests for long term reliability
are conducted to ensure a long life for every Quantum drive. These
tests have proven that the Pioneer SG drive will maintain Quantum's
high quality and reliable drive designs.
Future of Proximity Recording
The advances in areal density enabled by proximity
recording technology, such as Tri-NPAB heads, will act as the
basis for future low cost drive designs. The benefits gained from
the mature production processes of inductive thin-film heads like
the Tri-NPAB style may be leveraged for future head designs, such
as MR technologies. Even higher capacities than the Pioneer SG
design may be achievable using future generations of Tri-NPAB
With Tri-NPAB heads, areal density improvements
are being realized by drive designers to meet the rapidly increasing
storage requirements of today's entry-level PC systems. This second
generation of proximity recording heads are being combined with
advanced read channel designs to produce economical drives for
entry-level capacities. Quantum will continue the development
of multiple head technologies to meet the growing capacity and
performance requirements of PC end-users.