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# Prediction of Magnetic Slider Flatness Based on Lapping Plate Monitoring

IP.com Disclosure Number: IPCOM000016665D
Publication Date: 2003-Jul-08
Document File: 2 page(s) / 107K

## Publishing Venue

The IP.com Prior Art Database

## Abstract

The lapping rate of a disk drive air-bearing slider is found to follow the Preston law, which states the rate is linearly proportional to the relative velocity and the applied load. By measuring the Preston coefficient, the degradation of flatness in the sliders being lapped can be predicted.

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Prediction of Magnetic Slider Flatness Based on Lapping Plate Monitoring

The air-bearing surface (ABS) of sliders used in magnetic recording disk drives must have a certain flatness that is critical to the reliable read/write operation of a magnetic head. The slider ABS is defined by lapping the slider against a lapping plate. Variations of the lapping characteristics among prepared plates contribute significantly to variations in the slider ABS flatness. In addition a plate's characteristics change over the course of its life. Because it is hard to detect changes of intrinsic plate characteristics, there is not much preventive correction and prediction about the slider flatness. As a result state-of-the-art slider fabrication calls for a 100% inspection of slider ABS flatness.

It is desirable to predict changes in the slider flatness based on an in-situ assessment of a plate lapping characteristics through the course of a lapping plate life.

The lapping rate of a slider is found to follow the Preston law which states the rate is linearly proportional to the relative velocity and the applied load as

Rate = Preston_Coefficient * Velocity * Load

The Preston coefficient is a complex function of lapping condition, such as the property of plate topology and the fluid dynamics of the lapping fluid. One can compute the Preston coefficient by measuring the velocity, load and lapping rate during lapping.

As a plate is worn through lapping, the Preston coefficient also decreases. Interestingly the slider flatness also degrades, as the chart shown. Therefore,...