Lubricating oil for fluid dynamic bearing in 2.5 inch hard disk drive motor

In this research, lubricating oil was developed for fluid dynamic bearing (FDB) that can be used in 2.5 inch HDD. The characteristics of base oils that effect on the potential usage of lubricant in fluid dynamic bearing for 2.5 inch HDD were studied. The preparation of base oil samples and properties assessment were performed. Finally, finished lubricants were improved and their properties were assessed such as flash point, outgas, friction coefficient and service life test. The results showed that finished lubricant which could be used in FDB spindle motor of 2.5 inch HDD can be prepared from a mixture of base oils prepared from DOS and DOA (1:1) and then blended with antioxidant additive, antiwear additive and metal deactivator additive at 2%, 1% and 0.05% w/w, respectively. This finished lubricant has kinematic viscosity at 9.67 mm²/s at 40℃, wear scar at 0.31 mm., % weight loss at 0.289 (85℃ x 3 hrs.), outgas at 1,394 ng/g (85℃x 3 hrs.) and friction coefficient by SRV at 0.097 (50℃), Moreover, it has excellent long service life and weight loss properties which are better than those of commercial available lubricant.