Tribological characterization of lapping lubricant in hard disk drive fabrication

One of the most important processes in hard disk drive fabrication is the lapping process. As two bodies are in contact, the friction occurs, and the softer material can be worn out by the harder. By using lubricant in the lapping process, it does not only reduce the friction, but it also transfers heat and captures debris away from the surface contacts. This thesis work focused on the effects of tribological parameters toward the characteristics of lubricants, using ball-on-disk tribometer. The tribological behaviors between using different base lubricants were investigated. At the same condition as final lapping process, EG-based and oil-based lubricants exhibited the average coefficient of friction (after 100 contact cycles) at about 0.089± 0.115 and 0.023±0.012, respectively. These values were much lower than without lubricants. Scanning electron microscopy results confirmed deeper and wilder wear tracks on dry lubricant than those with lubricants. Dry surface exhibited the boundary regime, which the normal load and sliding speed has no influence on its friction regime. By using oil-based lubricant, the friction regime transited from mixed to boundary regime, as the normal load increased. Applying EG-based lubricant, the friction regime transited from mixed for lower sliding speed to hydrodynamic regime for higher sliding speed at 0.1N but transited from mixed regime to boundary regime at 0.5N instead. Moreover, the effects of adding additives in EG based lubricant were also studied. It was found that by added surfactant on EG-based lubricant its friction belongs to boundary regime. While added corrosion inhibitors its friction belongs to mixed regimes.