Development of FDB spindle motors for HDD use

Hard disk drives (HDD) are improving rapidly in recording density and transfer rate every year. A significant factor contributing to their evolution is the spindle motor. Development of a spindle motor using a fluid dynamic bearing (FDB) is desirable as conventional spindle motors incorporating ball bearings are expected to reach their limitation technically in the near future. In this paper we discuss the trends of HDD, requirements for HDD spindle motors, motor construction, problems in relation to magnetic circuits, and constituent FDB technologies.