Actuator Bearing Greases: Their Effect on Aerosol Contamination in Disk Drives

Head stiction problems have driven the search for new actuator bearing greases. It is well known in the industry that heads gradually accumulate e organic products which lead to stiction seizures after the heads have landed on the disks. Actuator pivot bearings were lubricated by the test greases. Three grease types were tested: 1) mineral oil with a polyurea thickener, 2) polyolester oil with a polyurea thickener, and 3) perfluorinated polyether oil with a polytetrafluorethelyne thickener. Airborne particle count tests were performed on five files each to assess the grease effect on disk drive contamination levels. Particle counts for sizes 0.2, 0.5 and 1.0 micron were taken from accessing files. Differences in the generation rate of aerosolized grease were measured when the files were new and also after having been exercised 10, 20 and 60 million seeks. Cascade impaction of disk drive’s air stream was analyzed by time of flight secondary ion mass spectroscopy to confirm that the aerosol particles captured were from the grease. Files built with the perfluorinated polyether oil based grease had the lowest particle count. Files built with bearings lubricated by the mineral oil based grease had a moderate particle count. Files containing the polyol ester oil based grease had the highest particle count.