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Development of FDB spindle motors for HDD use

The areal recording density of an HDD has increased noticeably at a rate of 60% to 100% a year, and further increases are expected in the future. In line with this trend, increasingly exacting tolerances are required regarding off-track errors of heads. Ball bearings have been conventionally used in spindle motors. However, off-track errors caused by non-repeatable run outs (NRRO) are approaching the control limit. Expectations for the implementation of spindle motors incorporating fluid dynamic bearings (FDBs) are rising. In this paper, we discuss FDB spindle motors, which are thought of as the future mainstream of HDD.