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Proximity Recording Head Technology

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Quantum is using proximity recording heads in its new low cost desktop drives to meet the price and capacity demands of entry-level PCs.

Introduction

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 capacity growth.

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 SG.

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)


Prfig1.gif

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.

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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 style heads.

Conclusion

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.

See Also