Abrading – Precision device or process - or with condition responsive... – Computer controlled
Reexamination Certificate
2002-05-24
2004-09-21
Nguyen, George (Department: 3723)
Abrading
Precision device or process - or with condition responsive...
Computer controlled
C451S008000, C451S028000, C451S312000, C029S603150, C029S603180
Reexamination Certificate
active
06793557
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to magnetic recording heads used, for example, in disk drives; and more particularly the invention relates to a removable lapping guide used during lapping of a magnetic recording head.
2. Description of the Background Art
Disk drives using magnetic recording of digital information store most of the information in contemporary computer systems. A disk drive has at least one rotating disk with discrete concentric tracks of data. Each disk drive also has at least one recording head typically having a separate write element and read element for writing and reading the data on the tracks. The recording head is constructed on a slider and the slider is attached to a suspension. The combination of the recording head, slider, and suspension is called a head gimbal assembly. In addition, there is an actuator which positions the recording head over the specific track of interest. The actuator first rotates to seek the track of interest and after positioning the recording head over the track maintains the recording head in close registration to that track. The disk in a disk drive has a substrate and a magnetic layer on the substrate for magnetic recording. The slider carrying the recording head has a disk facing surface upon which an air bearing is constructed. The air bearing allows the slider to float on a cushion of air and to be positioned close to the disk surface. Alternatively, the slider surface facing the disk can be adapted for partial or continuous contact with the disk.
Recording heads are constructed on a wafer using thin film methods. After the construction of the recording heads, the wafer is typically sliced into rows. Each row will typically have 20 to 80 recording heads. The row is first lapped in order to give the final dimensions to the read and write elements. After lapping, the air bearings are then simultaneously constructed on one surface of the row. Individual sliders are then separated from the row. For very high recording density, row lapping does not deliver the required dimensional control of stripe height of the read element and throat height of the write element.
Improved read element stripe height control is achieved by separating individual sliders from the row prior to lapping and construction of the airbearing. This better control of stripe height is important because each new disk drive product generally has read elements which are smaller than those of previous products. This ever decreasing size of each new read element exacerbates the difficulty of controlling the stripe height during lapping.
Electrical lapping guides have been used to monitor the progress of lapping. Electrical lapping guides are thin films of resistive metal. These stripes of metal are partially removed during the lapping of the slider. Thus by measuring the resistance of the electrical lapping guide during lapping the progress of lapping the read element may be monitored. For example, U.S. Pat. No. 5,588,199 discloses a lapping guide for use with a single slider wherein the lapping guide is connected in parallel with the read element.
What is needed is a lapping guide which is suitable for use with individual sliders, offers an unambiguous indication of lapping progression, does not interfere with the read or write elements, and is capable of being removed or inactivated after the lapping has been completed.
SUMMARY OF THE INVENTION
The present invention provides an electrical lapping guide for use with individual sliders. The electrical lapping guide thus provided allows lapping to be monitored without the need for additional connection pads and without causing interference with the read or write elements.
In a preferred embodiment, the electrical lapping guide is a resistive thin film member having a relatively high resistance. One of the electrical leads forming a connection to the electrical lapping guide is connected to one of the read element connection pads. The other electrical lead forming a connection to the electrical lapping guide is connected to one of the write element connection pads. By these electrical connections, the resistance monitored during lapping unambiguously indicates the state of the electrical lapping guide.
One of the electrical connections to the electrical lapping guide can be shallow with respect to a surface of the slider and therefore removable by ion milling or reactive ion etching after lapping is complete. Removing the electrical circuit of the electrical lapping guide can eliminate interference with subsequent use of the read or write elements in the recording head.
Other aspects and advantages of the invention will become apparent from the following detailed description, which when taken in conjunction with the drawings, illustrate by way of example the principles of the invention.
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Bunch Richard D.
Reiley Timothy Clark
Nguyen George
Nunnelley Lewis D.
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