Gurinder P. Singh

Thin film thermocouple sensors for measurement of contact temperatures during slider asperity interaction on magnetic recording disks

Thin-film thermocouple sensors have been fabricated on a magnetic recording slider. Both the sensors and the reference junctions are located on the air bearing surface of the slider. The effective size of the junctions is 4 mu m, and response time is faster than 0.5 mu s. The sensitivity of these thermocouples is measured to be 7 mu V/ degrees C. The thermocouple signals obtained at the slider asperity contacts show a temperature rise of 1-5 degrees C. Incorporating the sensor dimensions and assuming asperities of 0.5 mu m width, the actual temperatures are estimated to be in the range of 90-450 degrees C. >

Mechanism for formation of whiskers on a flying magnetic recording slider

When large amounts of contaminant particles exist in magnetic hard disk drives, whiskers can form at the trailing end of the air bearing of the sliders. Through whisker formation, small particles can accumulate to form a mass comparable to the slider dimensions. Redeposition of these whiskers on the tapers of the slider can lead to a loss of air bearing and head crash. We present a systematic study of the whisker formation mechanism. By injecting fluorescent, spherical polystyrene-latex particles we find that virtually all particles in whiskers are deformed from the original spherical shape. This deformation indicates that particles must pass through the interface before they are collected in the whiskers. Whiskers grow at the tip and not at the base, and form an extension of the air bearing surface. Presence of liquid lubricant on the disk is necessary to form whiskers. The viscosity of the lubricant significantly affects whisker morphology and growth rate. The lower the viscosity, the faster the whisker growth, the shorter the life of the whisker, and the longer and thinner the whisker. >

Calibration of micron‐size thermocouples for measurements of surface temperature

Imbedded thin‐film thermocouples can be used for the measurement of transient surface temperatures with high spatial resolution and sensitivity. To minimize environmental effects it is desirable to have close proximity between the reference junction and the sensor junction. In this article, we present and compare two calibration techniques for such thermocouples. The first technique is a steady‐state technique and uses a focused laser beam with a diameter of 3 μm as a point heat source. This technique consists of two steps. The first step is an absolute, but spatially averaged temperature measurement with a resistive temperature sensor. In the second step, the uncalibrated thermocouple junction is translated to resolve the spatial temperature profile generated by the laser spot. Both measurements are then combined to provide an absolute calibration which is independent of the thermal properties of the imbedding material and of the absorbed laser power. We used a simple sensor design which consists of a Ni...

Laser gram load adjust for improved disk drive performance

A new manufacturing technology for enabling tight distribution of magnetic recording slider flying heights and lower slider disk spacings is described. The technique uses high intensity laser radiation to increase or decrease the suspension preload on the slider to change the flying height. The technique can be employed for tightening gram load or flying height distributions, contact avoidance or to adjust the magnetic recording capabilities of the disk drive.

Effect of disk roughness on slider dynamics

The effect of roughness on the static and dynamic behavior of a taper flat slider on particulate disks of varying roughness and a much smoother thin-film disk has been measured, using a capacitance technique. The results are compared to the behavior modeled for a perfectly smooth disk. The data on the thin-film disk agree very well with the modeling results, but significant differences are observed for the rougher particulate disks. The trailing-edge resting height at zero velocity is higher on rougher disks. At low velocities, the frequency of the normal air bearing mode on the particulate disks is significantly higher than on the thin-film disk. At higher disk velocities, the air bearing mode on the particulate disks is at a lower frequency than on the thin-film disk. This implies that the disk roughness makes the slider fly at an effectively higher flying height at these disk velocities. At low disk velocities the increase in the frequency of the air bearing mode could be due to disk asperity contacts. >

Laser Smoothing of the Load/Unload Tabs of Magnetic Recording Head Gimbal Assemblies

A novel technology to smooth the metal tab surfaces using a pulsed laser beam is applied to reduce the wear of the load/ unload ramps used in disk drives that employ load/unload technology. The laser pulse length, pulse energy and the pulse repetition rate are so chosen that they cause the surface layer of the load/unload tab, approximately 2-3 um deep, to melt and refreeze quickly. As the surface layer melts, the surface tension of the melt removes most of the micro roughness and a smooth surface is obtained. The reduction in the micro surface roughness is confirmed by the AFM traces and a sharp decrease in the light scattered from the tab surface. In wear tests, such tabs show a remarkable improvement in the wear of the plastic load/unload ramps, allowing 5-10 X more load/unload cycles for a given amount of ramp wear.