Upgrading and Repairing PCs

Head Sliders

The term slider is used to describe the body of material that supports the actual drive head itself. The slider is what actually floats or slides over the surface of the disk, carrying the head at the correct distance from the medium for reading and writing. Most sliders resemble a trimaran, with two outboard pods that float along the surface of the disk media and a central "hull" portion that actually carries the head and read/write gap. Figure 9.8 shows a typical slider. Note that the actual head, with the read/write gap, is on the trailing end of the slider.

The trend toward smaller and smaller form factor drives has forced sliders to become smaller as well. The typical mini-Winchester slider design is about .160''x.126''x.034'' in size. Most head manufacturers have now shifted to 50% smaller nanosliders, or 70% smaller picosliders. A nanoslider has dimensions of about .08''x.063''x.017'', whereas the smaller picoslider is .049''x.039''x.012''. Picosliders are assembled by using flex interconnect cable (FIC) and chip on ceramic (COC) technology that enables the process to be completely automated.

Smaller sliders reduce the mass carried at the end of the head actuator arms, which provides increased acceleration and deceleration and leads to faster seek times. The smaller sliders also require less area for a landing zone, thus increasing the usable area of the disk platters. Further, the smaller slider contact area reduces the slight wear on the platter surface that occurs during normal startup and spindown of the drive platters.

The newer nanoslider and picoslider designs also have specially modified surface patterns that are designed to maintain the same floating height above the disk surface, whether the slider is positioned above the inner or outer cylinders. Conventional sliders increase or decrease their floating heights considerably according to the velocity of the disk surface traveling beneath them. Above the outer cylinders, the velocity and floating height are higher. This arrangement is undesirable in newer drives that use zoned bit recording, in which the bit density is the same on all the cylinders. When the bit density is uniform throughout the drive, the head floating height should also be relatively constant for maximum performance. Special textured surface patterns and manufacturing techniques enable the sliders to float at a much more consistent height, making them ideal for zoned bit recording drives. For more information on zoned recording, see the section "Disk Formatting" in Chapter 10.