Optimized pad design for slider and method for making the same

Details Optimized pad design for slider and method for making the same Optimized pad design for slider and method for making the same

2000-10-13

2002-12-10

Ometz, David L. (Department: 2651)

Dynamic magnetic information storage or retrieval

Fluid bearing head support

Disk record

C360S234900, C360S235200, C360S236500

Reexamination Certificate

active

06493185

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates in general to magnetic storage devices, and more particularly to an optimized pad design for a slider and a method for making the same.
2. Description of Related Art
Disk drives are information storage devices that use a rotatable disk with concentric data tracks containing the information, a head or transducer for reading and/or writing data onto the various tracks, and an actuator connected to a carrier for the head for moving the head to the desired track and maintaining it over the track centerline during read or write operations. There are typically a plurality of disks separated by spacer rings and stacked on a hub that is rotated by a disk drive motor. A housing supports the drive motor and head actuator and surrounds the head and disk to provide a substantially sealed environment for the head-disk interface.
Thin-film magnetic heads have been increasingly used, in place of conventional monolithic magnetic heads, as magnetic heads in magnetic disk apparatuses for recording and reproducing data so that the size of the heads may be reduced. Further, attempts have been made to minimize the distance between the magnetic head and the recording medium (the flying height) to realize a very dense recording format. It has been known since the early days of magnetic recording that minimizing the-head-disk spacing is desirable because the amplitude of the read signal from the disk increases with decreasing head-disk spacing. Higher recording densities can thus be achieved.
In conventional magnetic recording disk drives, the head carrier is an air-bearing slider that rides on a bearing of air above the disk surface when the disk is rotating at its operational speed. The slider is maintained next to the disk surface by a relatively fragile suspension that connects the slider to the actuator. The slider is either biased toward the disk surface by a small spring force from the suspension, or is “self-loaded” to the disk surface by means of a “negative-pressure” air-bearing surface on the slider. Contact start/stop (CSS) disk drives operate with the slider in contact with the disk surface during start and stop operations when there is insufficient disk rotational speed to maintain the air bearing. In a magnetic disk apparatus using magnetic disks having a relatively small diameter and thus a relatively low peripheral speed, proposals have been made in which magnetic head does not levitate above the recording medium but normally contacts the recording medium and has a sliding engagement therewith. In such a case, the thin-film magnetic head is fabricated such that the supporting base structure of the magnetic head with the slider or the contact pad thereof is very light in weight and is biased with a relatively small elastic force so that the contact pressure of the magnetic head with the magnetic recording medium is small.
Accordingly, improved magnetic data recording may be achieved by having a magnetic recording head in close proximity to a moving magnetic recording disk. In the contact type magnetic heads, it is desired that the pole which normally contacts the magnetic recording medium is wear-resistant. The contact pad surrounds the distal end of the pole, and the wear of the pole is mitigated if the wear of the contact pad is small. Accordingly, it is preferable to make the contact pad from a material harder than a material of the base structure of the magnetic head. This may be accomplished using a protruding pad that extends the magnetic recording head to the surface of the magnetic recording disk which wears to just make contact with the disk surface.
A protruding pad may be formed over the region of the magnetic recording head. The protruding pad generally includes the alumina overcoat material sputtered during fabrication of the magnetic recording head and some part of the ceramic surface of the slider, which is typically made of a TiC/Al
2
O
3
composite that is referred to as N58. The protruding pad has to wear at a controllable rate and that is accomplished by controlling the area of the N58. The TiC/Al
2
O
3
composite area, or N58, wears slowly, whereas the Al
2
O
3
wears within minutes to it's asymptotic value.
However, during the process of forming the protruding pad, a photoresist mask must be aligned over the surface of the slider material so that material around the pad may be removed. Nevertheless, the alignment of the photoresist masks is difficult to control accurately. Thus, the area of the N58 in the pad is difficult to control. Yet, the inability to accurately control the area of the N58 in the pad causes the burnish rate of the protruding pad to vary. The wear rate will vary because the wear rate is very sensitive to the amount of the N58 area and the mask alignment tolerances of 5 microns lead to a nominal pad of 8 microns having anywhere from 37% to 162% of the required amount of N58. If the desired amount of pad area in N58 is smaller, e.g., 2 microns, then the error becomes unacceptably large.
It can be seen that there is a need for an optimized pad design for a slider that minimizes the effect of mask alignment tolerances to allow for a more consistent N58 pad area and hence a more controllable burnish rate of the protruding pad.
SUMMARY OF THE INVENTION
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses an optimized pad design for a slider that minimizes the effect of mask alignment tolerances to allow for a more consistent N58 pad area and hence a more controllable burnish rate of the protruding pad.
The present invention solves the above-described problems by using a pad area that can more easily be controlled and kept to an area that can burnish in a reasonable length of time acceptable for the file manufacturing process.
A protruding pad in accordance with the principles of the present invention includes a first portion and a second portion formed by processing material to form the first and second portion wherein at least a quantity of the first portion includes a first material type and the second portion includes a second material type, the protruding pad further including a boundary interface separating the first material type from the second material type, the boundary interface having a position on the first portion that is dependent upon an alignment tolerance for the processing and that defines a surface area for the material of the second type, wherein the surface area of the material of the second type is negligibly affected by the position of the boundary interface.
Other embodiments of a protruding pad in accordance with the principles of the invention may include alternative or optional additional aspects. One such aspect of the present invention is that the second material is a hard material and the first material is softer than the second material.
Another aspect of the present invention is that the first material includes aluminum oxide and the second material includes a composite of titanium carbide and aluminum oxide.
Another aspect of the present invention is that the surface area of the material of the second type is substantially constant and provides a predictable burnish rate.
Another aspect of the present invention is that the first portion includes a narrow vertical part and the second portion includes a horizontal part such that the first and second portions converge to form a generally T formation.
Another aspect of the present invention is that the first portion is flared to prevent debris collecting at the middle of the second portion from crossing the elements when the slider flies at various skew angles.
Another aspect of the present invention is that the horizontal part includes a width and a depth, wherein the width may be decreased and the depth increased in a manner such that the surface area of the material of the second type remains substantially constant.
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