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This paper reports the results of constant speed drag tests on disks with four different lubricants using an ultra-high vacuum (UHV) tribochamber equipped with a mass spectrometer (MS). An optical surface analyzer (OSA) is also used to observe lubricant migration. Based on the analysis of the experimental results, we propose that, in the case of diamond-like carbon (DLC)-coated sliders, the durability of a lubricant is dominated by its mobility, its ability to bond to the carbon overcoat and its thermal stability. However, in the case of uncoated sliders, the durability of the lubricant, is dominated by the strength of the lubricant layer formed on the carbon overcoat, the interaction between lubricant molecules and the Al2O3 of the slider surface, the degradation rate of the lubricants caused by catalysis of Al2O3, as well as thermal stability of lubricant. Reaction of Al2O3 with the oxygen atoms in the backbones of the molecules is the dominant factor in their catalytic degradation.

The optical surface analyzer (OSA) was found to be an excellent tool to examine the lubricant migration rate on thin film disks. Using the OSA it was found that the rate of lubricant migration increased as molecular weight decreased. An AM type perfluoropolyether with an aromatic end group and Z-Dol were also observed to have different migration rates for the same molecular weight. The migration rate of AM lubricant was increased significantly by the presence of X-1P as an additive in the lubricant system.

Fly-stiction is a special kind of stiction that occurs at the interface between a hard drive head and the hard disk. It can have very high values and has caused serious problems for the computer industry in the past. It is defined as that taken after a certain number of CSS cycles in the landing zone of a disk, followed by an extended period of time of sweep or track dwell in the data zone and finally an extended period of park time in the landing zone. This paper has studied the nature, mechanism and solutions of the high fly-stiction phenomenon. CSS testers, optical microscopes, an optical surface analyzer and a Fourier transform infrared spectrometer were used to measure fly-stiction values and analyze the test surfaces of heads and disks. The results obtained indicate that the fly-stiction value is much higher than the corresponding park-stiction value. The fly-stiction value does not change with increasing number of CSS cycles, and may decrease slightly with increasing lubricant thickness. In addition, a high fly-stiction value may be caused by a contamination of spindle grease. Finally, a high fly-stiction value can be reduced by avoiding contamination or increasing the resistance to contamination of a disk. For instance, an ion-beam carbon overcoat can reduce the fly-stiction to half the value obtained with a sputter carbon overcoat.

Thermal asperities (TA’s) are tribological events that cause repercussions for giant magnetoresistance (GMR) and MR heads in the hard disk drive industry. A TA is a read signal spike caused by sensor temperature rise due to contact with disk asperities or contaminant particles. TA events may cause GMR and MR heads to temporarily lose their reading capability, and may potentially damage the transducer. It is difficult to completely avoid particle contamination in hard drive applications. Hence it is necessary to design heads/media with a minimum TA sensitivity to particles. A test method for TA sensitivity to particles is needed. This work developed a test method for TA sensitivities to particles. The test system includes a CSS tester with TA detection capability, a chamber to contain the head/disk interface, a particle atomizer, and a particle counter. Aluminum silicate particles used in the test have sizes ranging from 0.2 to 1.0 μm. Particles are injected into the chamber during head scan for TA’s from ID to OD with adjustable air-borne concentrations in the chamber from 10×106 to 30×106particles/m3. TA counts of 30 scans are averaged to obtain reliable TA sensitivity data. Media with different lubricant thickness, different carbon overcoats, and different lubricant types are tested with this method. The results indicated that this methodology can effectively differentiate TA sensitivity to particles for the media studied.

Spinstand level testing has demonstrated a failure mechanism that may go undetected using standard strain gage and acoustic emission methods of data capture. Since normally static friction is higher than dynamic friction, dynamic friction measurements are often ignored, filtered, or sampled at a much lower data rate than static friction measurements. In this study, dynamic friction peak values significantly higher than the static friction were recorded during take-off of Pico heads on laser-textured media. Furthermore, data collected using an optical surfaceanalyzer (OSA) showed a greater degree of wear on disks exhibiting high dynamic friction. FFT was employed to analyze the signal modulation of the high dynamic friction event. Resonance at a frequency of approximately 1050 Hz was found to be associated with the high dynamic friction.Experiments were designed to reveal factors that influence this resonance occurrence. The factors identified that contribute to this resonance were natural frequency of the head load arm, disk bump pitch, and lubricant thickness. The head/disk interface system is believed to be excited by an improper bump pitch if the lubricant layer is not thick enough to reduce the friction value.